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Dhar K, Abinandan S, Sana T, Venkateswarlu K, Megharaj M. Anaerobic biodegradation of phenanthrene and pyrene by sulfate-reducing cultures enriched from contaminated freshwater lake sediments. ENVIRONMENTAL RESEARCH 2023; 235:116616. [PMID: 37437866 DOI: 10.1016/j.envres.2023.116616] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/26/2023] [Revised: 06/17/2023] [Accepted: 07/09/2023] [Indexed: 07/14/2023]
Abstract
Our current understanding of the susceptibility of hazardous polycyclic aromatic hydrocarbons (PAHs) to anaerobic microbial degradation is very limited. In the present study, we obtained phenanthrene- and pyrene-degrading strictly anaerobic sulfate-reducing enrichments using contaminated freshwater lake sediments as the source material. The highly enriched phenanthrene-degrading culture, MMKS23, was dominated (98%) by a sulfate-reducing bacterium belonging to the genus Desulfovibrio. While Desulfovibrio sp. was also predominant (79%) in the pyrene-degrading enrichment culture, MMKS44, an anoxygenic purple non-sulfur bacterium, Rhodopseudomonas sp., constituted a significant fraction (18%) of the total microbial community. Phenanthrene or pyrene biodegradation by the enrichment cultures was coupled with sulfate reduction, as evident from near stoichiometric consumption of sulfate and accumulation of sulfide. Also, there was almost complete inhibition of substrate degradation in the presence of an inhibitor of sulfate reduction, i.e., 20 mM MoO42-, in the culture medium. After 180 days of incubation, about 79.40 μM phenanthrene was degraded in the MMKS23 culture, resulting in the consumption of 806.80 μM sulfate and accumulation of 625.80 μM sulfide. Anaerobic pyrene biodegradation by the MMKS44 culture was relatively slow. About 22.30 μM of the substrate was degraded after 180 days resulting in the depletion of 239 μM sulfate and accumulation of 196.90 μM sulfide. Biodegradation of phenanthrene by the enrichment yielded a metabolite, phenanthrene-2-carboxylic acid, suggesting that carboxylation could be a widespread initial step of phenanthrene activation under sulfate-reducing conditions. Overall, this novel study demonstrates the ability of sulfate-reducing bacteria (SRB), dwelling in contaminated freshwater sediments to anaerobically biodegrade three-ringed phenanthrene and highly recalcitrant four-ringed pyrene. Our findings suggest that SRB could play a crucial role in the natural attenuation of PAHs in anoxic freshwater sediments.
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Affiliation(s)
- Kartik Dhar
- Global Centre for Environmental Remediation (GCER), College of Engineering, Science and Environment, University of Newcastle, Callaghan, NSW, 2308, Australia.
| | - Sudharsanam Abinandan
- Global Centre for Environmental Remediation (GCER), College of Engineering, Science and Environment, University of Newcastle, Callaghan, NSW, 2308, Australia; Cooperative Research Centre for Contamination Assessment and Remediation of the Environment (CRC CARE), University of Newcastle, Callaghan, NSW, 2308, Australia
| | - Tanmoy Sana
- Global Centre for Environmental Remediation (GCER), College of Engineering, Science and Environment, University of Newcastle, Callaghan, NSW, 2308, Australia
| | - Kadiyala Venkateswarlu
- Formerly Department of Microbiology, Sri Krishnadevaraya University, Anantapur, Andhra Pradesh, 515003, India
| | - Mallavarapu Megharaj
- Global Centre for Environmental Remediation (GCER), College of Engineering, Science and Environment, University of Newcastle, Callaghan, NSW, 2308, Australia; Cooperative Research Centre for Contamination Assessment and Remediation of the Environment (CRC CARE), University of Newcastle, Callaghan, NSW, 2308, Australia.
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Dhar K, Venkateswarlu K, Megharaj M. Anoxygenic phototrophic purple non-sulfur bacteria: tool for bioremediation of hazardous environmental pollutants. World J Microbiol Biotechnol 2023; 39:283. [PMID: 37594588 PMCID: PMC10439078 DOI: 10.1007/s11274-023-03729-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2023] [Accepted: 08/11/2023] [Indexed: 08/19/2023]
Abstract
The extraordinary metabolic flexibility of anoxygenic phototrophic purple non-sulfur bacteria (PNSB) has been exploited in the development of various biotechnological applications, such as wastewater treatment, biohydrogen production, improvement of soil fertility and plant growth, and recovery of high-value compounds. These versatile microorganisms can also be employed for the efficient bioremediation of hazardous inorganic and organic pollutants from contaminated environments. Certain members of PNSB, especially strains of Rhodobacter sphaeroides and Rhodopseudomonas palustris, exhibit efficient remediation of several toxic and carcinogenic heavy metals and metalloids, such as arsenic, cadmium, chromium, and lead. PNSB are also known to utilize diverse biomass-derived lignocellulosic organic compounds and xenobiotics. Although biodegradation of some substituted aromatic compounds by PNSB has been established, available information on the involvement of PNSB in the biodegradation of toxic organic pollutants is limited. In this review, we present advancements in the field of PNSB-based bioremediation of heavy metals and organic pollutants. Furthermore, we highlight that the potential role of PNSB as a promising bioremediation tool remains largely unexplored. Thus, this review emphasizes the necessity of investing extensive research efforts in the development of PNSB-based bioremediation technology.
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Affiliation(s)
- Kartik Dhar
- Global Centre for Environmental Remediation (GCER), College of Engineering, Science and Environment, University of Newcastle, Callaghan, NSW, 2308, Australia
- Department of Microbiology, Faculty of Biological Sciences, University of Chittagong, Chittagong, 4331, Bangladesh
| | - Kadiyala Venkateswarlu
- Formerly Department of Microbiology, Sri Krishnadevaraya University, Anantapuramu, Andhra Pradesh, 515003, India
| | - Mallavarapu Megharaj
- Global Centre for Environmental Remediation (GCER), College of Engineering, Science and Environment, University of Newcastle, Callaghan, NSW, 2308, Australia.
- Cooperative Research Centre for Contamination Assessment and Remediation of the Environment (CRC CARE), University of Newcastle, Callaghan, NSW, 2308, Australia.
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3
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Tec-Campos D, Posadas C, Tibocha-Bonilla JD, Thiruppathy D, Glonek N, Zuñiga C, Zepeda A, Zengler K. The genome-scale metabolic model for the purple non-sulfur bacterium Rhodopseudomonas palustris Bis A53 accurately predicts phenotypes under chemoheterotrophic, chemoautotrophic, photoheterotrophic, and photoautotrophic growth conditions. PLoS Comput Biol 2023; 19:e1011371. [PMID: 37556472 PMCID: PMC10441798 DOI: 10.1371/journal.pcbi.1011371] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2022] [Revised: 08/21/2023] [Accepted: 07/18/2023] [Indexed: 08/11/2023] Open
Abstract
The purple non-sulfur bacterium Rhodopseudomonas palustris is recognized as a critical microorganism in the nitrogen and carbon cycle and one of the most common members in wastewater treatment communities. This bacterium is metabolically extremely versatile. It is capable of heterotrophic growth under aerobic and anaerobic conditions, but also able to grow photoautotrophically as well as mixotrophically. Therefore R. palustris can adapt to multiple environments and establish commensal relationships with other organisms, expressing various enzymes supporting degradation of amino acids, carbohydrates, nucleotides, and complex polymers. Moreover, R. palustris can degrade a wide range of pollutants under anaerobic conditions, e.g., aromatic compounds such as benzoate and caffeate, enabling it to thrive in chemically contaminated environments. However, many metabolic mechanisms employed by R. palustris to breakdown and assimilate different carbon and nitrogen sources under chemoheterotrophic or photoheterotrophic conditions remain unknown. Systems biology approaches, such as metabolic modeling, have been employed extensively to unravel complex mechanisms of metabolism. Previously, metabolic models have been reconstructed to study selected capabilities of R. palustris under limited experimental conditions. Here, we developed a comprehensive metabolic model (M-model) for R. palustris Bis A53 (iDT1294) consisting of 2,721 reactions, 2,123 metabolites, and comprising 1,294 genes. We validated the model using high-throughput phenotypic, physiological, and kinetic data, testing over 350 growth conditions. iDT1294 achieved a prediction accuracy of 90% for growth with various carbon and nitrogen sources and close to 80% for assimilation of aromatic compounds. Moreover, the M-model accurately predicts dynamic changes of growth and substrate consumption rates over time under nine chemoheterotrophic conditions and demonstrated high precision in predicting metabolic changes between photoheterotrophic and photoautotrophic conditions. This comprehensive M-model will help to elucidate metabolic processes associated with the assimilation of multiple carbon and nitrogen sources, anoxygenic photosynthesis, aromatic compound degradation, as well as production of molecular hydrogen and polyhydroxybutyrate.
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Affiliation(s)
- Diego Tec-Campos
- Facultad de Ingeniería Química, Universidad Autónoma de Yucatán, Mérida, Yucatán, México
- Department of Pediatrics, University of California, San Diego, La Jolla, California, United States of America
| | - Camila Posadas
- Facultad de Ingeniería Química, Universidad Autónoma de Yucatán, Mérida, Yucatán, México
| | - Juan D. Tibocha-Bonilla
- Bioinformatics and Systems Biology Graduate Program, University of California, San Diego, La Jolla, California, United States of America
| | - Deepan Thiruppathy
- Department of Pediatrics, University of California, San Diego, La Jolla, California, United States of America
- Department of Bioengineering, University of California, San Diego, La Jolla California, United States of America
| | - Nathan Glonek
- Department of Pediatrics, University of California, San Diego, La Jolla, California, United States of America
| | - Cristal Zuñiga
- Department of Pediatrics, University of California, San Diego, La Jolla, California, United States of America
| | - Alejandro Zepeda
- Facultad de Ingeniería Química, Universidad Autónoma de Yucatán, Mérida, Yucatán, México
| | - Karsten Zengler
- Department of Pediatrics, University of California, San Diego, La Jolla, California, United States of America
- Department of Bioengineering, University of California, San Diego, La Jolla California, United States of America
- Center for Microbiome Innovation, University of California, San Diego, La Jolla, California, United States of America
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4
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Schaerer LG, Wu R, Putman LI, Pearce JM, Lu T, Shonnard DR, Ong RG, Techtmann SM. Killing two birds with one stone: chemical and biological upcycling of polyethylene terephthalate plastics into food. Trends Biotechnol 2023; 41:184-196. [PMID: 36058768 DOI: 10.1016/j.tibtech.2022.06.012] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2022] [Revised: 05/24/2022] [Accepted: 06/21/2022] [Indexed: 01/24/2023]
Abstract
Most polyethylene terephthalate (PET) plastic waste is landfilled or pollutes the environment. Additionally, global food production must increase to support the growing population. This article explores the feasibility of using microorganisms in an industrial system that upcycles PET into edible microbial protein powder to solve both problems simultaneously. Many microorganisms can utilize plastics as feedstock, and the resultant microbial biomass contains fats, nutrients, and proteins similar to those found in human diets. While microbial degradation of PET is promising, biological PET depolymerization is too slow to resolve the global plastic crisis and projected food shortages. Evidence reviewed here suggests that by coupling chemical depolymerization and biological degradation of PET, and using cooperative microbial communities, microbes can efficiently convert PET waste into food.
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Affiliation(s)
- Laura G Schaerer
- Department of Biological Sciences, Michigan Technological University, Houghton, MI, USA
| | - Ruochen Wu
- Department of Chemical Engineering, Michigan Technological University, Houghton, MI, USA
| | - Lindsay I Putman
- Department of Biological Sciences, Michigan Technological University, Houghton, MI, USA
| | - Joshua M Pearce
- Department of Electrical and Computer Engineering, Western University, London, Ontario, Canada
| | - Ting Lu
- Department of Bioengineering, University of Illinois Urbana-Champaign, Champaign, IL, USA
| | - David R Shonnard
- Department of Chemical Engineering, Michigan Technological University, Houghton, MI, USA
| | - Rebecca G Ong
- Department of Chemical Engineering, Michigan Technological University, Houghton, MI, USA
| | - Stephen M Techtmann
- Department of Biological Sciences, Michigan Technological University, Houghton, MI, USA.
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Saulnier BK, Siahkamari M, Singh SK, Nejad M, Hodge DB. Effect of Dilute Acid Pretreatment and Lignin Extraction Conditions on Lignin Properties and Suitability as a Phenol Replacement in Phenol-Formaldehyde Wood Adhesives. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2023; 71:592-602. [PMID: 36562625 DOI: 10.1021/acs.jafc.2c07299] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/17/2023]
Abstract
Corn stover was subjected to dilute sulfuric acid pretreatment to assess the impact of pretreatment conditions on lignin extractability, properties, and utility as a phenol replacement in wood phenol-formaldehyde (PF) adhesives. It was identified that both formic acid and NaOH could extract and recover 60-70% of the lignin remaining after pretreatment and enzymatic hydrolysis under the mildest pretreatment conditions while simultaneously achieving reasonable enzymatic hydrolysis yields (>60%). The availability of reaction sites for the incorporation of lignins into the PF polymer matrix (i.e., unsubstituted phenolic hydroxyl groups) was shown to be strongly impacted by the pretreatment time and the recovery. Finally, a lignin-based wood adhesive was formulated by replacing 100% of the phenol with formic-acid-extracted lignin, which exhibited a dry shear strength exceeding a conventional PF adhesive. These findings suggest that both pretreatment and lignin extraction conditions can be tailored to yield lignins with properties targeted for this co-product application.
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Affiliation(s)
- Brian K Saulnier
- Department of Chemical & Biological Engineering, Montana State University, Bozeman, Montana 59717, United States
| | - Mohsen Siahkamari
- Department of Forestry, Michigan State University, East Lansing, Michigan 48824, United States
| | - Sandip K Singh
- Department of Chemical & Biological Engineering, Montana State University, Bozeman, Montana 59717, United States
| | - Mojgan Nejad
- Department of Forestry, Michigan State University, East Lansing, Michigan 48824, United States
| | - David B Hodge
- Department of Chemical & Biological Engineering, Montana State University, Bozeman, Montana 59717, United States
- Division of Sustainable Process Engineering, Luleå University of Technology, Luleå 97187, Sweden
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Brown B, Wilkins M, Saha R. Rhodopseudomonas palustris: A biotechnology chassis. Biotechnol Adv 2022; 60:108001. [PMID: 35680002 DOI: 10.1016/j.biotechadv.2022.108001] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2022] [Revised: 05/18/2022] [Accepted: 06/01/2022] [Indexed: 11/26/2022]
Abstract
Rhodopseudomonas palustris is an attractive option for biotechnical applications and industrial engineering due to its metabolic versatility and its ability to catabolize a wide variety of feedstocks and convert them to several high-value products. Given its adaptable metabolism, R. palustris has been studied and applied in an extensive variety of applications such as examining metabolic tradeoffs for environmental perturbations, biodegradation of aromatic compounds, environmental remediation, biofuel production, agricultural biostimulation, and bioelectricity production. This review provides a holistic summary of the commercial applications for R. palustris as a biotechnology chassis and suggests future perspectives for research and engineering.
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Affiliation(s)
- Brandi Brown
- Department of Biological Systems Engineering, University of Nebraska-Lincoln, Lincoln, NE 68583, USA
| | - Mark Wilkins
- Department of Biological Systems Engineering, University of Nebraska-Lincoln, Lincoln, NE 68583, USA; Industrial Agricultural Products Center, University of Nebraska-Lincoln, Lincoln, NE 68583, USA; Department of Food Science and Technology, University of Nebraska-Lincoln, Lincoln, NE 68588, USA
| | - Rajib Saha
- Department of Chemical and Biomolecular Engineering, University of Nebraska-Lincoln, Lincoln, NE 68588, USA.
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Li M, Ning P, Sun Y, Luo J, Yang J. Characteristics and Application of Rhodopseudomonas palustris as a Microbial Cell Factory. Front Bioeng Biotechnol 2022; 10:897003. [PMID: 35646843 PMCID: PMC9133744 DOI: 10.3389/fbioe.2022.897003] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2022] [Accepted: 04/27/2022] [Indexed: 01/20/2023] Open
Abstract
Rhodopseudomonas palustris, a purple nonsulfur bacterium, is a bacterium with the properties of extraordinary metabolic versatility, carbon source diversity and metabolite diversity. Due to its biodetoxification and biodegradation properties, R. palustris has been traditionally applied in wastewater treatment and bioremediation. R. palustris is rich in various metabolites, contributing to its application in agriculture, aquaculture and livestock breeding as additives. In recent years, R. palustris has been engineered as a microbial cell factory to produce valuable chemicals, especially photofermentation of hydrogen. The outstanding property of R. palustris as a microbial cell factory is its ability to use a diversity of carbon sources. R. palustris is capable of CO2 fixation, contributing to photoautotrophic conversion of CO2 into valuable chemicals. R. palustris can assimilate short-chain organic acids and crude glycerol from industrial and agricultural wastewater. Lignocellulosic biomass hydrolysates can also be degraded by R. palustris. Utilization of these feedstocks can reduce the industry cost and is beneficial for environment. Applications of R. palustris for biopolymers and their building blocks production, and biofuels production are discussed. Afterward, some novel applications in microbial fuel cells, microbial electrosynthesis and photocatalytic synthesis are summarized. The challenges of the application of R. palustris are analyzed, and possible solutions are suggested.
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Affiliation(s)
- Meijie Li
- Energy-Rich Compound Production by Photosynthetic Carbon Fixation Research Center, Shandong Key Lab of Applied Mycology, Qingdao Agricultural University, Qingdao, China
- College of Life Sciences, Qingdao Agricultural University, Qingdao, China
| | - Peng Ning
- Energy-Rich Compound Production by Photosynthetic Carbon Fixation Research Center, Shandong Key Lab of Applied Mycology, Qingdao Agricultural University, Qingdao, China
- College of Life Sciences, Qingdao Agricultural University, Qingdao, China
| | - Yi Sun
- Haiyang Comprehensive Administrative Law Enforcement Bureau (Agriculture), Haiyang, China
| | - Jie Luo
- Qingdao Garden Forestry Technology School, Qingdao, China
- *Correspondence: Jie Luo, ; Jianming Yang,
| | - Jianming Yang
- Energy-Rich Compound Production by Photosynthetic Carbon Fixation Research Center, Shandong Key Lab of Applied Mycology, Qingdao Agricultural University, Qingdao, China
- College of Life Sciences, Qingdao Agricultural University, Qingdao, China
- *Correspondence: Jie Luo, ; Jianming Yang,
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Zhu D, Qaria MA, Zhu B, Sun J, Yang B. Extremophiles and extremozymes in lignin bioprocessing. RENEWABLE AND SUSTAINABLE ENERGY REVIEWS 2022; 157:112069. [DOI: 10.1016/j.rser.2021.112069] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/01/2023]
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Immethun CM, Kathol M, Changa T, Saha R. Synthetic Biology Tool Development Advances Predictable Gene Expression in the Metabolically Versatile Soil Bacterium Rhodopseudomonas palustris. Front Bioeng Biotechnol 2022; 10:800734. [PMID: 35372317 PMCID: PMC8966681 DOI: 10.3389/fbioe.2022.800734] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2021] [Accepted: 02/16/2022] [Indexed: 11/13/2022] Open
Abstract
Harnessing the unique biochemical capabilities of non-model microorganisms would expand the array of biomanufacturing substrates, process conditions, and products. There are non-model microorganisms that fix nitrogen and carbon dioxide, derive energy from light, catabolize methane and lignin-derived aromatics, are tolerant to physiochemical stresses and harsh environmental conditions, store lipids in large quantities, and produce hydrogen. Model microorganisms often only break down simple sugars and require low stress conditions, but they have been engineered for the sustainable manufacture of numerous products, such as fragrances, pharmaceuticals, cosmetics, surfactants, and specialty chemicals, often by using tools from synthetic biology. Transferring complex pathways has proven to be exceedingly difficult, as the cofactors, cellular conditions, and energy sources necessary for this pathway to function may not be present in the host organism. Utilization of unique biochemical capabilities could also be achieved by engineering the host; although, synthetic biology tools developed for model microbes often do not perform as designed in other microorganisms. The metabolically versatile Rhodopseudomonas palustris CGA009, a purple non-sulfur bacterium, catabolizes aromatic compounds derived from lignin in both aerobic and anaerobic conditions and can use light, inorganic, and organic compounds for its source of energy. R. palustris utilizes three nitrogenase isozymes to fulfill its nitrogen requirements while also generating hydrogen. Furthermore, the bacterium produces two forms of RuBisCo in response to carbon dioxide/bicarbonate availability. While this potential chassis harbors many beneficial traits, stable heterologous gene expression has been problematic due to its intrinsic resistance to many antibiotics and the lack of synthetic biology parts investigated in this microbe. To address these problems, we have characterized gene expression and plasmid maintenance for different selection markers, started a synthetic biology toolbox specifically for the photosynthetic R. palustris, including origins of replication, fluorescent reporters, terminators, and 5′ untranslated regions, and employed the microbe’s endogenous plasmid for exogenous protein production. This work provides essential synthetic biology tools for engineering R. palustris’ many unique biochemical processes and has helped define the principles for expressing heterologous genes in this promising microbe through a methodology that could be applied to other non-model microorganisms.
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10
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Gao Y, Yuan L, Du J, Wang H, Yang X, Duan L, Zheng L, Bahar MM, Zhao Q, Zhang W, Liu Y, Fu Z, Wang W, Naidu R. Bacterial community profile of the crude oil-contaminated saline soil in the Yellow River Delta Natural Reserve, China. CHEMOSPHERE 2022; 289:133207. [PMID: 34890619 DOI: 10.1016/j.chemosphere.2021.133207] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/01/2021] [Revised: 12/04/2021] [Accepted: 12/06/2021] [Indexed: 06/13/2023]
Abstract
Crude oil contamination greatly influence soil bacterial community. Proliferative microbes in the crude oil-contaminated soil are closely related to the living conditions. Oil wells in the Yellow River Delta Natural Reserve (YRDNR) region is an ideal site for investigating the bacterial community of crude oil-contaminated saline soil. In the present study, 18 soil samples were collected from the depths of 0-20 cm and 20-40 cm around the oil wells in the YRDNR. The bacterial community profile was analyzed through high-throughput sequencing to trace the oil-degrading aerobic and anaerobic bacteria. The results indicated that C15-C28 and C29-C38 were the main fractions of total petroleum hydrocarbon (TPH) in the sampled soil. These TPH fractions had a significant negative effect on bacterial biodiversity (Shannon, Simpson, and Chao1 indices), which led to the proliferation of hydrocarbon-degrading bacteria. A comprehensive analysis between the environmental factors and soil microbial community structure showed that Streptococcus, Bacillus, Sphingomonas, and Arthrobacter were the aerobic hydrocarbon-degrading bacteria; unidentified Rhodobacteraceae and Porticoccus were considered to be the possible facultative anaerobic bacteria with hydrocarbon biodegradation ability; Acidithiobacillus, SAR324 clade, and Nitrosarchaeum were predicted to be the anaerobic hydrocarbon-degrading bacteria in the sub-surface soil. Furthermore, large amount of carbon sources derived from TPH was found to cause depletion of bioavailable nitrogen in the soil. The bacteria associated with nitrogen transformation, such as Solirubrobacter, Candidatus Udaeobacter, Lysinibacillus, Bradyrhizobium, Sphingomonas, Mycobacterium, and Acidithiobacillus, were highly abundant; these bacteria may possess the ability to increase nitrogen availability in the crude oil-contaminated soil. The bacterial community functions were significantly different between the surface and the sub-surface soil, and the dissolved oxygen concentration in soil was considered to be potential influencing factor. Our results could provide useful information for the bioremediation of crude oil-contaminated saline soil.
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Affiliation(s)
- Yongchao Gao
- Qilu University of Technology (Shandong Academy of Sciences), Ecology Institute, Shandong Provincial Key Laboratory of Applied Microbiology, 28789 East Jingshi Road, Jinan, 250103, China.
| | - Liyuan Yuan
- Qilu University of Technology (Shandong Academy of Sciences), Ecology Institute, Shandong Provincial Key Laboratory of Applied Microbiology, 28789 East Jingshi Road, Jinan, 250103, China
| | - Jianhua Du
- Global Centre for Environmental Remediation, Faculty of Science, University of Newcastle, Callaghan, NSW, 2308, Australia
| | - Hui Wang
- School of Resources and Environment, University of Jinan, Jinan, 250022, China
| | - Xiaodong Yang
- Department of Geography & Spatial Information Technology, Ningbo University, Ningbo, 315211, China.
| | - Luchun Duan
- Global Centre for Environmental Remediation, Faculty of Science, University of Newcastle, Callaghan, NSW, 2308, Australia
| | - Liwen Zheng
- Qilu University of Technology (Shandong Academy of Sciences), Ecology Institute, Shandong Provincial Key Laboratory of Applied Microbiology, 28789 East Jingshi Road, Jinan, 250103, China
| | - Md Mezbaul Bahar
- Global Centre for Environmental Remediation, Faculty of Science, University of Newcastle, Callaghan, NSW, 2308, Australia
| | - Qingqing Zhao
- Qilu University of Technology (Shandong Academy of Sciences), Ecology Institute, Shandong Provincial Key Laboratory of Applied Microbiology, 28789 East Jingshi Road, Jinan, 250103, China
| | - Wen Zhang
- Qilu University of Technology (Shandong Academy of Sciences), Ecology Institute, Shandong Provincial Key Laboratory of Applied Microbiology, 28789 East Jingshi Road, Jinan, 250103, China
| | - Yanju Liu
- Global Centre for Environmental Remediation, Faculty of Science, University of Newcastle, Callaghan, NSW, 2308, Australia
| | - Zhaoyang Fu
- Qilu University of Technology (Shandong Academy of Sciences), Ecology Institute, Shandong Provincial Key Laboratory of Applied Microbiology, 28789 East Jingshi Road, Jinan, 250103, China
| | - Wei Wang
- Qilu University of Technology (Shandong Academy of Sciences), Ecology Institute, Shandong Provincial Key Laboratory of Applied Microbiology, 28789 East Jingshi Road, Jinan, 250103, China
| | - Ravi Naidu
- Global Centre for Environmental Remediation, Faculty of Science, University of Newcastle, Callaghan, NSW, 2308, Australia; Cooperative Research Centre for Contamination Assessment and Remediation of the Environment, Callaghan, NSW, 2308, Australia
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11
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Harwood CS. Rhodopseudomonas palustris. Trends Microbiol 2021; 30:307-308. [PMID: 34933806 DOI: 10.1016/j.tim.2021.12.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2021] [Revised: 11/29/2021] [Accepted: 12/01/2021] [Indexed: 10/19/2022]
Affiliation(s)
- Caroline S Harwood
- Department of Microbiology, University of Washington, Seattle, WA 98195-7735, USA.
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12
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Alsiyabi A, Brown B, Immethun C, Long D, Wilkins M, Saha R. Synergistic experimental and computational approach identifies novel strategies for polyhydroxybutyrate overproduction. Metab Eng 2021; 68:1-13. [PMID: 34464732 DOI: 10.1016/j.ymben.2021.08.008] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2021] [Revised: 07/28/2021] [Accepted: 08/25/2021] [Indexed: 11/28/2022]
Abstract
Polyhydroxybutyrate (PHB) is a sustainable bioplastic produced by bacteria that is a potential replacement for conventional plastics. This study delivers an integrated experimental and computational modeling approach to decipher metabolic factors controlling PHB production and offers engineering design strategies to boost production. In the metabolically robust Rhodopseudomonas palustris CGA009, PHB production significantly increased when grown on the carbon- and electron-rich lignin breakdown product p-coumarate (C9H8O3) compared to virtually no PHB titer from acetate (C2H3NaO2). The maximum yield did not improve further when grown on coniferyl alcohol (C10H12O3), but comparison of the PHB profiles showed that coniferyl alcohol's higher carbon content resulted in a higher rate of PHB production. Combined experimental results revealed that cytoplasmic space may be a limiting factor for maximum PHB titer. In order to obtain a systems-level understanding of factors driving PHB yield, a model-driven investigation was performed. The model yielded several engineering design strategies including utilizing reduced, high molecular weight substrates that bypass the thiolase reaction (phaA). Based on these strategies, utilization of butyrate was predicted and subsequently validated to produce PHB. Model analysis also explained why nitrogen starvation was not essential for PHB production and revealed that renewable and abundant lignin aromatics are ideal candidates for PHB production. Most importantly, the generality of the derived design rules allows them to be applied to any PHB-producing microbe with similar metabolic features.
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Affiliation(s)
- Adil Alsiyabi
- Department of Chemical and Biomolecular Engineering, University of Nebraska-Lincoln, Lincoln, NE, 68588, USA
| | - Brandi Brown
- Department of Biological Systems Engineering, University of Nebraska-Lincoln, Lincoln, NE, 68583, USA
| | - Cheryl Immethun
- Department of Chemical and Biomolecular Engineering, University of Nebraska-Lincoln, Lincoln, NE, 68588, USA
| | - Dianna Long
- Department of Biological Systems Engineering, University of Nebraska-Lincoln, Lincoln, NE, 68583, USA
| | - Mark Wilkins
- Department of Biological Systems Engineering, University of Nebraska-Lincoln, Lincoln, NE, 68583, USA; Industrial Agricultural Products Center, University of Nebraska-Lincoln, Lincoln, NE, 68583, USA; Department of Food Science and Technology, University of Nebraska-Lincoln, Lincoln, NE, 68588, USA
| | - Rajib Saha
- Department of Chemical and Biomolecular Engineering, University of Nebraska-Lincoln, Lincoln, NE, 68588, USA.
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Sogani M, Pankan AO, Dongre A, Yunus K, Fisher AC. Augmenting the biodegradation of recalcitrant ethinylestradiol using Rhodopseudomonas palustris in a hybrid photo-assisted microbial fuel cell with enhanced bio-hydrogen production. JOURNAL OF HAZARDOUS MATERIALS 2021; 408:124421. [PMID: 33199150 DOI: 10.1016/j.jhazmat.2020.124421] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/11/2020] [Revised: 10/26/2020] [Accepted: 10/27/2020] [Indexed: 06/11/2023]
Abstract
This study presents the biodegradation potential of ethinylestradiol (EE2) in anaerobic environments using exoelectrogenic activity of Rhodopseudomonas palustris. EE2, a basic ingredient in oral contraceptives, is a significant estrogenic micropollutant in various wastewaters and is considered highly recalcitrant. This recalcitrance of EE2 has caused anoxic areas to become repositories for these pollutants. Thus, it is essential to find the microorganisms and suitable methods to degrade this compound. An initial EE2 concentration of 1 mg/L, used in an anaerobic photobioreactor, resulted in 70% EE2 degradation over a period of 16 days with an increase of 63% in hydrogen production when EE2 was used with glycerol as the main carbon source in the culture medium. Furthermore, in the novel setup of hybrid photo-assisted microbial fuel cell (h-PMFC) employed here, EE2 degradation enhanced to 89.82% with a maximum power density of 0.633 ± 0.04 mW/m2. The hybrid MFC employed here could metabolize EE2 and sustained the bio-hydrogen production for 14 days to run the hydrogen fuel cell which otherwise could not be sustained with glycerol only and thus increased the overall power output. The current work highlights the use of R. palustris and the significance of co-metabolism in bioremediation of pollutants and bioenergy generation.
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Affiliation(s)
- Monika Sogani
- Department of Chemical Engineering and Biotechnology, University of Cambridge, Philippa Fawcett Drive, Cambridge, United Kingdom CB3 0AS; School of Civil and Chemical Engineering, Manipal University Jaipur, Dehmi Kalan, Off Jaipur Ajmer Express Highway, Jaipur, India 303007.
| | - Aazraa O Pankan
- Department of Chemical Engineering and Biotechnology, University of Cambridge, Philippa Fawcett Drive, Cambridge, United Kingdom CB3 0AS
| | - Aman Dongre
- Department of Chemical Engineering and Biotechnology, University of Cambridge, Philippa Fawcett Drive, Cambridge, United Kingdom CB3 0AS; School of Civil and Chemical Engineering, Manipal University Jaipur, Dehmi Kalan, Off Jaipur Ajmer Express Highway, Jaipur, India 303007
| | - Kamran Yunus
- Department of Chemical Engineering and Biotechnology, University of Cambridge, Philippa Fawcett Drive, Cambridge, United Kingdom CB3 0AS
| | - Adrian C Fisher
- Department of Chemical Engineering and Biotechnology, University of Cambridge, Philippa Fawcett Drive, Cambridge, United Kingdom CB3 0AS
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Redundancy in aromatic O-demethylation and ring opening reactions in Novosphingobium aromaticivorans and their impact in the metabolism of plant derived phenolics. Appl Environ Microbiol 2021; 87:AEM.02794-20. [PMID: 33579679 PMCID: PMC8091115 DOI: 10.1128/aem.02794-20] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Lignin is a plant heteropolymer composed of phenolic subunits. Because of its heterogeneity and recalcitrance, the development of efficient methods for its valorization still remains an open challenge. One approach to utilize lignin is its chemical deconstruction into mixtures of monomeric phenolic compounds followed by biological funneling into a single product. Novosphingobium aromaticivorans DSM12444 has been previously engineered to produce 2-pyrone-4,6-dicarboxylic acid (PDC) from depolymerized lignin by simultaneously metabolizing multiple aromatics through convergent routes involving the intermediates 3-methoxygallic acid (3-MGA) and protocatechuic acid (PCA). We investigated enzymes predicted to be responsible for O-demethylation and oxidative aromatic ring opening, two critical reactions involved in the metabolism of phenolics compounds by N. aromaticivorans The results showed the involvement of DesA in O-demethylation of syringic and vanillic acids, LigM in O-demethylation of vanillic acid and 3-MGA, and a new O-demethylase, DmtS, in the conversion of 3-MGA into gallic acid (GA). In addition, we found that LigAB was the main aromatic ring opening dioxygenase involved in 3-MGA, PCA, and GA metabolism, and that a previously uncharacterized dioxygenase, LigAB2, had high activity with GA. Our results indicate a metabolic route not previously identified in N. aromaticivorans that involves O-demethylation of 3-MGA to GA. We predict this pathway channels ∼15% of the carbon flow from syringic acid, with the rest following ring opening of 3-MGA. The new knowledge obtained in this study allowed for the creation of an improved engineered strain for the funneling of aromatic compounds that exhibits stoichiometric conversion of syringic acid into PDC.IMPORTANCE For lignocellulosic biorefineries to effectively contribute to reduction of fossil fuel use, they need to become efficient at producing chemicals from all major components of plant biomass. Making products from lignin will require engineering microorganisms to funnel multiple phenolic compounds to the chemicals of interest, and N. aromaticivorans is a promising chassis for this technology. The ability of N. aromaticivorans to efficiently and simultaneously degrade many phenolic compounds may be linked to having functionally redundant aromatic degradation pathways and enzymes with broad substrate specificity. A detailed knowledge of aromatic degradation pathways is thus essential to identify genetic engineering targets to maximize product yields. Furthermore, knowledge of enzyme substrate specificity is critical to redirect flow of carbon to desired pathways. This study described an uncharacterized pathway in N. aromaticivorans and the enzymes that participate in this pathway, allowing the engineering of an improved strain for production of PDC from lignin.
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Ma Y, Donohue TJ, Noguera DR. Kinetic modeling of anaerobic degradation of plant-derived aromatic mixtures by Rhodopseudomonas palustris. Biodegradation 2021; 32:179-192. [PMID: 33675449 PMCID: PMC7997838 DOI: 10.1007/s10532-021-09932-3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2020] [Accepted: 02/23/2021] [Indexed: 11/23/2022]
Abstract
Rhodopseudomonas palustris is a model microorganism for studying the anaerobic metabolism of aromatic compounds. While it is well documented which aromatics can serve as sole organic carbon sources, co-metabolism of other aromatics is poorly understood. This study used kinetic modeling to analyze the simultaneous degradation of aromatic compounds present in corn stover hydrolysates and model the co-metabolism of aromatics not known to support growth of R. palustris as sole organic substrates. The simulation predicted that p-coumaroyl amide and feruloyl amide were hydrolyzed to p-coumaric acid and ferulic acid, respectively, and further transformed via p-coumaroyl-CoA and feruloyl-CoA. The modeling also suggested that metabolism of p-hydroxyphenyl aromatics was slowed by substrate inhibition, whereas the transformation of guaiacyl aromatics was inhibited by their p-hydroxyphenyl counterparts. It also predicted that substrate channeling may occur during degradation of p-coumaroyl-CoA and feruloyl-CoA, resulting in no detectable accumulation of p-hydroxybenzaldehyde and vanillin, during the transformation of these CoA ligated compounds to p-hydroxybenzoic acid and vanillic acid, respectively. While the simulation correctly represented the known transformation of p-hydroxybenzoic acid via the benzoyl-CoA pathway, it also suggested co-metabolism of vanillic acid and syringic acid, which are known not to serve as photoheterotrophic growth substrate for R. palustris.
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Affiliation(s)
- Yanjun Ma
- Great Lakes Bioenergy Research Center, Wisconsin Energy Institute, University of Wisconsin-Madison, Madison, WI, 53726, USA
| | - Timothy J Donohue
- Great Lakes Bioenergy Research Center, Wisconsin Energy Institute, University of Wisconsin-Madison, Madison, WI, 53726, USA.,Department of Bacteriology, University of Wisconsin-Madison, Madison, WI, 53706, USA
| | - Daniel R Noguera
- Great Lakes Bioenergy Research Center, Wisconsin Energy Institute, University of Wisconsin-Madison, Madison, WI, 53726, USA. .,Department of Civil and Environmental Engineering, University of Wisconsin-Madison, Madison, WI, 53706, USA.
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Rhodopseudomonas palustris CGA009 polyhydroxybutyrate production from a lignin aromatic and quantification via flow cytometry. ACTA ACUST UNITED AC 2020. [DOI: 10.1016/j.biteb.2020.100474] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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Lo KJ, Lee SK, Liu CT. Development of a low-cost culture medium for the rapid production of plant growth-promoting Rhodopseudomonas palustris strain PS3. PLoS One 2020; 15:e0236739. [PMID: 32730333 PMCID: PMC7392278 DOI: 10.1371/journal.pone.0236739] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2020] [Accepted: 07/13/2020] [Indexed: 02/07/2023] Open
Abstract
Rhodopseudomonas palustris PS3 is one of the purple phototrophic non-sulfur bacteria (PNSB), which have plant growth-promoting effects on various plants. To expand the scale of PS3 fermentation in a time- and cost-effective fashion, the purpose of this work was to evaluate the use of low-cost materials as culture media and to optimize the culture conditions via response surface methodology. Corn steep liquor (CSL) and molasses were identified as potential materials to replace the nitrogen and carbon sources, respectively, in the conventional growth medium. The optimum culture conditions identified through central composite design were CSL, 39.41 mL/L; molasses, 32.35 g/L; temperature, 37.9°C; pH, 7.0; and DO 30%. Under the optimized conditions, the biomass yield reached 2.18 ± 0.01 g/L at 24 hours, which was 7.8-fold higher than that under the original medium (0.28 ± 0.01 g/L). The correlation between the predicted and experimental values of the model was over 98%, which verified the validity of the response models. Furthermore, we verified the effectiveness of the R. palustris PS3 inoculant grown under the newly developed culture conditions for plant growth promotion. This study provides a potential strategy for improving the fermentation of R. palustris PS3 in low-cost media for large-scale industrial production.
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Affiliation(s)
- Kai-Jiun Lo
- Institute of Biotechnology, National Taiwan University, Taipei, Taiwan
| | - Sook-Kuan Lee
- Institute of Biotechnology, National Taiwan University, Taipei, Taiwan
| | - Chi-Te Liu
- Institute of Biotechnology, National Taiwan University, Taipei, Taiwan
- Agricultural Biotechnology Research Center, Academia Sinica, Nankang, Taipei, Taiwan
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18
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Common problems associated with the microbial productions of aromatic compounds and corresponding metabolic engineering strategies. Biotechnol Adv 2020; 41:107548. [DOI: 10.1016/j.biotechadv.2020.107548] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2019] [Revised: 04/06/2020] [Accepted: 04/08/2020] [Indexed: 01/06/2023]
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Weiss R, Guebitz GM, Pellis A, Nyanhongo GS. Harnessing the Power of Enzymes for Tailoring and Valorizing Lignin. Trends Biotechnol 2020; 38:1215-1231. [PMID: 32423726 DOI: 10.1016/j.tibtech.2020.03.010] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2019] [Revised: 03/17/2020] [Accepted: 03/19/2020] [Indexed: 02/07/2023]
Abstract
Lignin, a structural component of lignocellulosic plants, is an alternative raw material with enormous potential to replace diminishing fossil-based resources for the sustainable production of many chemicals and materials. Unfortunately, lignin's heterogeneity, low reactivity, and strong intra- and intermolecular hydrogen interactions and modifications introduced during the pulping process present significant technical challenges. However, the increasing ability to tailor lignin biosynthesis pathways by targeting enzymes and the continued discovery of more robust biocatalysts are enabling the synthesis of novel valuable products. This review summarizes how enzymes involved in lignin biosynthesis pathways and microbial enzymes are being harnessed to produce chemicals and materials and to upgrade lignin properties for the synthesis of a variety of value-added lignin industrial products.
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Affiliation(s)
- Renate Weiss
- University of Natural Resources and Life Sciences, Vienna, Institute of Environmental Biotechnology, Konrad Lorenz Straße 20, 3430, Tulln an der Donau, Austria
| | - Georg M Guebitz
- University of Natural Resources and Life Sciences, Vienna, Institute of Environmental Biotechnology, Konrad Lorenz Straße 20, 3430, Tulln an der Donau, Austria; Austrian Centre for Industrial Biotechnology (ACIB), Konrad Lorenz Strasse 20, 3430, Tulln an der Donau, Austria
| | - Alessandro Pellis
- University of Natural Resources and Life Sciences, Vienna, Institute of Environmental Biotechnology, Konrad Lorenz Straße 20, 3430, Tulln an der Donau, Austria
| | - Gibson S Nyanhongo
- University of Natural Resources and Life Sciences, Vienna, Institute of Environmental Biotechnology, Konrad Lorenz Straße 20, 3430, Tulln an der Donau, Austria; Austrian Centre for Industrial Biotechnology (ACIB), Konrad Lorenz Strasse 20, 3430, Tulln an der Donau, Austria.
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20
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Anaerobic Degradation of Syringic Acid by an Adapted Strain of Rhodopseudomonas palustris. Appl Environ Microbiol 2020; 86:AEM.01888-19. [PMID: 31732577 PMCID: PMC6974649 DOI: 10.1128/aem.01888-19] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2019] [Accepted: 11/13/2019] [Indexed: 01/06/2023] Open
Abstract
Lignin is the most abundant aromatic polymer on Earth and a resource that could eventually substitute for fossil fuels as a source of aromatic compounds for industrial and biotechnological applications. Engineering microorganisms for the production of aromatic-based biochemicals requires detailed knowledge of the metabolic pathways for the degradation of aromatics that are present in lignin. Our isolation and analysis of a Rhodopseudomonas palustris strain capable of syringic acid degradation reveal a previously unknown metabolic route for aromatic degradation in R. palustris. This study highlights several key features of this pathway and sets the stage for a more complete understanding of the microbial metabolic repertoire required to metabolize aromatic compounds from lignin and other renewable sources. While lignin represents a major fraction of the carbon in plant biomass, biological strategies to convert the components of this heterogeneous polymer into products of industrial and biotechnological value are lacking. Syringic acid (3,5-dimethoxy-4-hydroxybenzoic acid) is a by-product of lignin degradation, appearing in lignocellulosic hydrolysates, deconstructed lignin streams, and other agricultural products. Rhodopseudomonas palustris CGA009 is a known degrader of phenolic compounds under photoheterotrophic conditions via the benzoyl coenzyme A (CoA) degradation (BAD) pathway. However, R. palustris CGA009 is reported to be unable to metabolize meta-methoxylated phenolics, such as syringic acid. We isolated a strain of R. palustris (strain SA008.1.07), adapted from CGA009, which can grow on syringic acid under photoheterotrophic conditions, utilizing it as a sole source of organic carbon and reducing power. An SA008.1.07 mutant with an inactive benzoyl-CoA reductase structural gene was able to grow on syringic acid, demonstrating that the metabolism of this aromatic compound is not through the BAD pathway. Comparative gene expression analyses of SA008.1.07 implicated the involvement of products of the vanARB operon (rpa3619, rpa3620, rpa3621), which has been described as catalyzing aerobic aromatic ring demethylation in other bacteria, in anaerobic syringic acid degradation. In addition, experiments with a vanARB deletion mutant demonstrated the involvement of the vanARB operon in anaerobic syringic acid degradation. These observations provide new insights into the anaerobic degradation of meta-methoxylated and other aromatics by R. palustris. IMPORTANCE Lignin is the most abundant aromatic polymer on Earth and a resource that could eventually substitute for fossil fuels as a source of aromatic compounds for industrial and biotechnological applications. Engineering microorganisms for the production of aromatic-based biochemicals requires detailed knowledge of the metabolic pathways for the degradation of aromatics that are present in lignin. Our isolation and analysis of a Rhodopseudomonas palustris strain capable of syringic acid degradation reveal a previously unknown metabolic route for aromatic degradation in R. palustris. This study highlights several key features of this pathway and sets the stage for a more complete understanding of the microbial metabolic repertoire required to metabolize aromatic compounds from lignin and other renewable sources.
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Modeling the Interplay between Photosynthesis, CO 2 Fixation, and the Quinone Pool in a Purple Non-Sulfur Bacterium. Sci Rep 2019; 9:12638. [PMID: 31477760 PMCID: PMC6718658 DOI: 10.1038/s41598-019-49079-z] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2019] [Accepted: 08/19/2019] [Indexed: 11/17/2022] Open
Abstract
Rhodopseudomonas palustris CGA009 is a purple non-sulfur bacterium that can fix carbon dioxide (CO2) and nitrogen or break down organic compounds for its carbon and nitrogen requirements. Light, inorganic, and organic compounds can all be used for its source of energy. Excess electrons produced during its metabolic processes can be exploited to produce hydrogen gas or biodegradable polyesters. A genome-scale metabolic model of the bacterium was reconstructed to study the interactions between photosynthesis, CO2 fixation, and the redox state of the quinone pool. A comparison of model-predicted flux values with available Metabolic Flux Analysis (MFA) fluxes yielded predicted errors of 5–19% across four different growth substrates. The model predicted the presence of an unidentified sink responsible for the oxidation of excess quinols generated by the TCA cycle. Furthermore, light-dependent energy production was found to be highly dependent on the quinol oxidation rate. Finally, the extent of CO2 fixation was predicted to be dependent on the amount of ATP generated through the electron transport chain, with excess ATP going toward the energy-demanding Calvin-Benson-Bassham (CBB) pathway. Based on this analysis, it is hypothesized that the quinone redox state acts as a feed-forward controller of the CBB pathway, signaling the amount of ATP available.
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Liu Q, Tang J, Liu X, Song B, Zhen M, Ashbolt NJ. Vertical response of microbial community and degrading genes to petroleum hydrocarbon contamination in saline alkaline soil. J Environ Sci (China) 2019; 81:80-92. [PMID: 30975332 DOI: 10.1016/j.jes.2019.02.001] [Citation(s) in RCA: 32] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2018] [Revised: 02/01/2019] [Accepted: 02/03/2019] [Indexed: 06/09/2023]
Abstract
A column microcosm was conducted by amending crude oil into Dagang Oilfield soil to simulate the bioremediation process. The dynamic change of microbial communities and metabolic genes in vertical depth soil from 0 to 80 cm were characterized to evaluate the petroleum degradation potential of indigenous microorganism. The influence of environmental variables on the microbial responds to petroleum contamination were analyzed. Degradation extent of 42.45% of n-alkanes (C8-C40) and 34.61% of 16ΣPAH were reached after 22 weeks. Relative abundance of alkB, nah, and phe gene showed about 10-fold increment in different depth of soil layers. Result of HTS profiles demonstrated that Pseudomonas, Marinobacter and Lactococcus were the major petroleum-degrading bacteria in 0-30 and 30-60 cm depth of soils. Fusarium and Aspergillus were the dominant oil-degrading fungi in the 0-60 cm depth of soils. In 60-80 cm deep soil, anaerobic bacteria such as Bacteroidetes, Lactococcus, and Alcanivorax played important roles in petroleum degradation. Redundancy analysis (RDA) and correlation analysis demonstrated that petroleum hydrocarbons (PHs) as well as soil salinity, clay content, and anaerobic conditions were the dominant effect factors on microbial community compositions in 0-30, 30-60, and 60-80 cm depth of soils, respectively.
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Affiliation(s)
- Qinglong Liu
- College of Environmental Science and Engineering, Nankai University, Tianjin 300071, China..
| | - Jingchun Tang
- College of Environmental Science and Engineering, Nankai University, Tianjin 300071, China.; Key Laboratory of Pollution Processes and Environmental Criteria (Ministry of Education), Tianjin 300071, China; Tianjin Engineering Research Center of Environmental Diagnosis and Contamination Remediation, Tianjin 300071, China.
| | - Xiaomei Liu
- College of Environmental Science and Engineering, Nankai University, Tianjin 300071, China
| | - Benru Song
- College of Environmental Science and Engineering, Nankai University, Tianjin 300071, China
| | - Meinan Zhen
- College of Environmental Science and Engineering, Nankai University, Tianjin 300071, China
| | - Nicholas J Ashbolt
- School of Public Health, University of Alberta, Edmonton, Alberta T6G 2G7, Canada
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Phototrophic Lactate Utilization by Rhodopseudomonas palustris Is Stimulated by Coutilization with Additional Substrates. Appl Environ Microbiol 2019; 85:AEM.00048-19. [PMID: 30902855 DOI: 10.1128/aem.00048-19] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2019] [Accepted: 03/14/2019] [Indexed: 01/09/2023] Open
Abstract
The phototrophic purple nonsulfur bacterium Rhodopseudomonas palustris is known for its metabolic versatility and is of interest for various industrial and environmental applications. Despite decades of research on R. palustris growth under diverse conditions, patterns of R. palustris growth and carbon utilization with mixtures of carbon substrates remain largely unknown. R. palustris readily utilizes most short-chain organic acids but cannot readily use lactate as a sole carbon source. Here we investigated the influence of mixed-substrate utilization on phototrophic lactate consumption by R. palustris We found that lactate was simultaneously utilized with a variety of other organic acids and glycerol in time frames that were insufficient for R. palustris growth on lactate alone. Thus, lactate utilization by R. palustris was expedited by its coutilization with additional substrates. Separately, experiments using carbon pairs that did not contain lactate revealed acetate-mediated inhibition of glycerol utilization in R. palustris This inhibition was specific to the acetate-glycerol pair, as R. palustris simultaneously utilized acetate or glycerol when either was paired with succinate or lactate. Overall, our results demonstrate that (i) R. palustris commonly employs simultaneous mixed-substrate utilization, (ii) mixed-substrate utilization expands the spectrum of readily utilized organic acids in this species, and (iii) R. palustris has the capacity to exert carbon catabolite control in a substrate-specific manner.IMPORTANCE Bacterial carbon source utilization is frequently assessed using cultures provided single carbon sources. However, the utilization of carbon mixtures by bacteria (i.e., mixed-substrate utilization) is of both fundamental and practical importance; it is central to bacterial physiology and ecology, and it influences the utility of bacteria as biotechnology. Here we investigated mixed-substrate utilization by the model organism Rhodopseudomonas palustris Using mixtures of organic acids and glycerol, we show that R. palustris exhibits an expanded range of usable carbon substrates when provided substrates in mixtures. Specifically, coutilization enabled the prompt consumption of lactate, a substrate that is otherwise not readily used by R. palustris Additionally, we found that R. palustris utilizes acetate and glycerol sequentially, revealing that this species has the capacity to use some substrates in a preferential order. These results provide insights into R. palustris physiology that will aid the use of R. palustris for industrial and commercial applications.
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Lubbers RJM, Dilokpimol A, Visser J, Mäkelä MR, Hildén KS, de Vries RP. A comparison between the homocyclic aromatic metabolic pathways from plant-derived compounds by bacteria and fungi. Biotechnol Adv 2019; 37:107396. [PMID: 31075306 DOI: 10.1016/j.biotechadv.2019.05.002] [Citation(s) in RCA: 49] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2018] [Revised: 04/18/2019] [Accepted: 05/03/2019] [Indexed: 12/13/2022]
Abstract
Aromatic compounds derived from lignin are of great interest for renewable biotechnical applications. They can serve in many industries e.g. as biochemical building blocks for bioplastics or biofuels, or as antioxidants, flavor agents or food preservatives. In nature, lignin is degraded by microorganisms, which results in the release of homocyclic aromatic compounds. Homocyclic aromatic compounds can also be linked to polysaccharides, tannins and even found freely in plant biomass. As these compounds are often toxic to microbes already at low concentrations, they need to be degraded or converted to less toxic forms. Prior to ring cleavage, the plant- and lignin-derived aromatic compounds are converted to seven central ring-fission intermediates, i.e. catechol, protocatechuic acid, hydroxyquinol, hydroquinone, gentisic acid, gallic acid and pyrogallol through complex aromatic metabolic pathways and used as energy source in the tricarboxylic acid cycle. Over the decades, bacterial aromatic metabolism has been described in great detail. However, the studies on fungal aromatic pathways are scattered over different pathways and species, complicating a comprehensive view of fungal aromatic metabolism. In this review, we depicted the similarities and differences of the reported aromatic metabolic pathways in fungi and bacteria. Although both microorganisms share the main conversion routes, many alternative pathways are observed in fungi. Understanding the microbial aromatic metabolic pathways could lead to metabolic engineering for strain improvement and promote valorization of lignin and related aromatic compounds.
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Affiliation(s)
- Ronnie J M Lubbers
- Fungal Physiology, Westerdijk Fungal Biodiversity Institute & Fungal Molecular Physiology, Utrecht University, Uppsalalaan 8, 3584 CT Utrecht, the Netherlands.
| | - Adiphol Dilokpimol
- Fungal Physiology, Westerdijk Fungal Biodiversity Institute & Fungal Molecular Physiology, Utrecht University, Uppsalalaan 8, 3584 CT Utrecht, the Netherlands.
| | - Jaap Visser
- Fungal Physiology, Westerdijk Fungal Biodiversity Institute & Fungal Molecular Physiology, Utrecht University, Uppsalalaan 8, 3584 CT Utrecht, the Netherlands.
| | - Miia R Mäkelä
- Department of Microbiology, University of Helsinki, Viikinkaari 9, Helsinki, Finland.
| | - Kristiina S Hildén
- Department of Microbiology, University of Helsinki, Viikinkaari 9, Helsinki, Finland.
| | - Ronald P de Vries
- Fungal Physiology, Westerdijk Fungal Biodiversity Institute & Fungal Molecular Physiology, Utrecht University, Uppsalalaan 8, 3584 CT Utrecht, the Netherlands; Department of Microbiology, University of Helsinki, Viikinkaari 9, Helsinki, Finland.
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25
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Advances in microbial lignin degradation and its applications. Curr Opin Biotechnol 2019; 56:179-186. [DOI: 10.1016/j.copbio.2018.11.011] [Citation(s) in RCA: 87] [Impact Index Per Article: 17.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2018] [Revised: 11/14/2018] [Accepted: 11/14/2018] [Indexed: 12/29/2022]
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Lo KJ, Lin SS, Lu CW, Kuo CH, Liu CT. Whole-genome sequencing and comparative analysis of two plant-associated strains of Rhodopseudomonas palustris (PS3 and YSC3). Sci Rep 2018; 8:12769. [PMID: 30143697 PMCID: PMC6109142 DOI: 10.1038/s41598-018-31128-8] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2018] [Accepted: 08/13/2018] [Indexed: 11/14/2022] Open
Abstract
Rhodopseudomonas palustris strains PS3 and YSC3 are purple non-sulfur phototrophic bacteria isolated from Taiwanese paddy soils. PS3 has beneficial effects on plant growth and enhances the uptake efficiency of applied fertilizer nutrients. In contrast, YSC3 has no significant effect on plant growth. The genomic structures of PS3 and YSC3 are similar; each contains one circular chromosome that is 5,269,926 or 5,371,816 bp in size, with 4,799 or 4,907 protein-coding genes, respectively. In this study, a large class of genes involved in chemotaxis and motility was identified in both strains, and genes associated with plant growth promotion, such as nitrogen fixation-, IAA synthesis- and ACC deamination-associated genes, were also identified. We noticed that the growth rate, the amount of biofilm formation, and the relative expression levels of several chemotaxis-associated genes were significantly higher for PS3 than for YSC3 upon treatment with root exudates. These results indicate that PS3 responds better to the presence of plant hosts, which may contribute to the successful interactions of PS3 with plant hosts. Moreover, these findings indicate that the existence of gene clusters associated with plant growth promotion is required but not sufficient for a bacterium to exhibit phenotypes associated with plant growth promotion.
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Affiliation(s)
- Kai-Jiun Lo
- Institute of Biotechnology, National Taiwan University, Taipei, 106, Taiwan
| | - Shih-Shun Lin
- Institute of Biotechnology, National Taiwan University, Taipei, 106, Taiwan.,Agricultural Biotechnology Research Center, Academia Sinica, Taipei, 115, Taiwan.,Center of Biotechnology, National Taiwan University, Taipei, 106, Taiwan.,National Center for High-Performance Computing, National Applied Research Laboratories, Hsinchu, 300, Taiwan
| | - Chia-Wei Lu
- Center for Shrimp Disease Control and Genetic Improvement, National Cheng Kung University, Tainan, 701, Taiwan
| | - Chih-Horng Kuo
- Institute of Plant and Microbial Biology, Academia Sinica, Taipei, 115, Taiwan. .,Molecular and Biological Agricultural Sciences Program, Taiwan International Graduate Program, National Chung Hsing University and Academia Sinica, Taipei, 115, Taiwan. .,Graduate Institute of Biotechnology, National Chung Hsing University, Taichung City, 402, Taiwan.
| | - Chi-Te Liu
- Institute of Biotechnology, National Taiwan University, Taipei, 106, Taiwan. .,Agricultural Biotechnology Research Center, Academia Sinica, Taipei, 115, Taiwan.
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Scarborough MJ, Lynch G, Dickson M, McGee M, Donohue TJ, Noguera DR. Increasing the economic value of lignocellulosic stillage through medium-chain fatty acid production. BIOTECHNOLOGY FOR BIOFUELS 2018; 11:200. [PMID: 30034526 PMCID: PMC6052542 DOI: 10.1186/s13068-018-1193-x] [Citation(s) in RCA: 45] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/05/2018] [Accepted: 07/06/2018] [Indexed: 05/14/2023]
Abstract
BACKGROUND Lignocellulosic biomass is seen as an abundant renewable source of liquid fuels and chemicals that are currently derived from petroleum. When lignocellulosic biomass is used for ethanol production, the resulting liquid residue (stillage) contains large amounts of organic material that could be further transformed into recoverable bioproducts, thus enhancing the economics of the biorefinery. RESULTS Here we test the hypothesis that a bacterial community could transform the organics in stillage into valuable bioproducts. We demonstrate the ability of this microbiome to convert stillage organics into medium-chain fatty acids (MCFAs), identify the predominant community members, and perform a technoeconomic analysis of recovering MCFAs as co-products of ethanol production. Steady-state operation of a stillage-fed bioreactor showed that 18% of the organic matter in stillage was converted to MCFAs. Xylose and complex carbohydrates were the primary substrates transformed. During the MCFA production period, the five major genera represented more than 95% of the community, including Lactobacillus, Roseburia, Atopobium, Olsenella, and Pseudoramibacter. To assess the potential benefits of producing MCFAs from stillage, we modeled the economics of ethanol and MCFA co-production, at MCFA productivities observed during reactor operation. CONCLUSIONS The analysis predicts that production of MCFAs, ethanol, and electricity could reduce the minimum ethanol selling price from $2.15 to $1.76 gal-1 ($2.68 gal-1 gasoline equivalents) when compared to a lignocellulosic biorefinery that produces only ethanol and electricity.
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Affiliation(s)
- Matthew J. Scarborough
- The Great Lakes Bioenergy Research Center, University of Wisconsin-Madison, Madison, WI USA
- Department of Civil and Environmental Engineering, University of Wisconsin-Madison, Madison, WI USA
| | - Griffin Lynch
- The Great Lakes Bioenergy Research Center, University of Wisconsin-Madison, Madison, WI USA
- Department of Chemical and Biological Engineering, University of Wisconsin-Madison, Madison, WI USA
| | - Mitch Dickson
- The Great Lakes Bioenergy Research Center, University of Wisconsin-Madison, Madison, WI USA
- Department of Chemical and Biological Engineering, University of Wisconsin-Madison, Madison, WI USA
| | - Mick McGee
- The Great Lakes Bioenergy Research Center, University of Wisconsin-Madison, Madison, WI USA
| | - Timothy J. Donohue
- The Great Lakes Bioenergy Research Center, University of Wisconsin-Madison, Madison, WI USA
- Department of Bacteriology, University of Wisconsin-Madison, Madison, WI USA
| | - Daniel R. Noguera
- The Great Lakes Bioenergy Research Center, University of Wisconsin-Madison, Madison, WI USA
- Department of Civil and Environmental Engineering, University of Wisconsin-Madison, Madison, WI USA
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Rosa LT, Dix SR, Rafferty JB, Kelly DJ. Structural basis for high-affinity adipate binding to AdpC (RPA4515), an orphan periplasmic-binding protein from the tripartite tricarboxylate transporter (TTT) family in Rhodopseudomonas palustris. FEBS J 2017; 284:4262-4277. [PMID: 29082669 DOI: 10.1111/febs.14304] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2017] [Revised: 09/27/2017] [Accepted: 10/19/2017] [Indexed: 01/24/2023]
Abstract
The tripartite tricarboxylate transporter (TTT) family is a poorly characterised group of prokaryotic secondary solute transport systems, which employ a periplasmic substrate-binding protein (SBP) for initial ligand recognition. The substrates of only a small number of TTT systems are known and very few SBP structures have been solved, so the mechanisms of SBP-ligand interactions in this family are not well understood. The SBP RPA4515 (AdpC) from Rhodopseudomonas palustris was found by differential scanning fluorescence and isothermal titration calorimetry to bind aliphatic dicarboxylates of a chain length of six to nine carbons, with KD values in the μm range. The highest affinity was found for the C6-dicarboxylate adipate (1,6-hexanedioate). Crystal structures of AdpC, either adipate or 2-oxoadipate bound, revealed a lack of positively charged amino acids in the binding pocket and showed that water molecules are involved in bridging hydrogen bonds to the substrate, a conserved feature in the TTT SBP family that is distinct from other types of SBP. In AdpC, both of the ligand carboxylate groups and a linear chain conformation are needed for coordination in the binding pocket. RT-PCR showed that adpC expression is upregulated by low environmental adipate concentrations, suggesting adipate is a physiologically relevant substrate but as adpC is not genetically linked to any TTT membrane transport genes, the role of AdpC may be in signalling rather than transport. Our data expand the known ligands for TTT systems and identify a novel high-affinity binding protein for adipate, an important industrial chemical intermediate and food additive. DATABASES Protein structure co-ordinates are available in the PDB under the accession numbers 5OEI and 5OKU.
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Affiliation(s)
- Leonardo T Rosa
- Department of Molecular Biology and Biotechnology, The University of Sheffield, Sheffield, UK
| | - Samuel R Dix
- Department of Molecular Biology and Biotechnology, The University of Sheffield, Sheffield, UK
| | - John B Rafferty
- Department of Molecular Biology and Biotechnology, The University of Sheffield, Sheffield, UK
| | - David J Kelly
- Department of Molecular Biology and Biotechnology, The University of Sheffield, Sheffield, UK
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Gall DL, Ralph J, Donohue TJ, Noguera DR. Biochemical transformation of lignin for deriving valued commodities from lignocellulose. Curr Opin Biotechnol 2017; 45:120-126. [DOI: 10.1016/j.copbio.2017.02.015] [Citation(s) in RCA: 67] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2016] [Revised: 02/06/2017] [Accepted: 02/24/2017] [Indexed: 11/30/2022]
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Abstract
Lipids from microbes offer a promising source of renewable alternatives to petroleum-derived compounds. In particular, oleaginous microbes are of interest because they accumulate a large fraction of their biomass as lipids. In this study, we analyzed genetic changes that alter lipid accumulation in Rhodobacter sphaeroides. By screening an R. sphaeroides Tn5 mutant library for insertions that increased fatty acid content, we identified 10 high-lipid (HL) mutants for further characterization. These HL mutants exhibited increased sensitivity to drugs that target the bacterial cell envelope and changes in shape, and some had the ability to secrete lipids, with two HL mutants accumulating ~60% of their total lipids extracellularly. When one of the highest-lipid-secreting strains was grown in a fed-batch bioreactor, its lipid content was comparable to that of oleaginous microbes, with the majority of the lipids secreted into the medium. Based on the properties of these HL mutants, we conclude that alterations of the cell envelope are a previously unreported approach to increase microbial lipid production. We also propose that this approach may be combined with knowledge about biosynthetic pathways, in this or other microbes, to increase production of lipids and other chemicals. This paper reports on experiments to understand how to increase microbial lipid production. Microbial lipids are often cited as one renewable replacement for petroleum-based fuels and chemicals, but strategies to increase the yield of these compounds are needed to achieve this goal. While lipid biosynthesis is often well understood, increasing yields of these compounds to industrially relevant levels is a challenge, especially since genetic, synthetic biology, or engineering approaches are not feasible in many microbes. We show that altering the bacterial cell envelope can be used to increase microbial lipid production. We also find that the utility of some of these alterations can be enhanced by growing cells in bioreactor configurations that can be used industrially. We propose that our findings can inform current and future efforts to increase production of microbial lipids, other fuels, or chemicals that are currently derived from petroleum.
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Shen Y, Jarboe L, Brown R, Wen Z. A thermochemical–biochemical hybrid processing of lignocellulosic biomass for producing fuels and chemicals. Biotechnol Adv 2015; 33:1799-813. [DOI: 10.1016/j.biotechadv.2015.10.006] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2015] [Revised: 10/16/2015] [Accepted: 10/16/2015] [Indexed: 12/28/2022]
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