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Vongkampang T, Sreenivas K, Grey C, van Niel EWJ. Immobilization techniques improve volumetric hydrogen productivity of Caldicellulosiruptor species in a modified continuous stirred tank reactor. Biotechnol Biofuels Bioprod 2023; 16:25. [PMID: 36793132 PMCID: PMC9933333 DOI: 10.1186/s13068-023-02273-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/20/2022] [Accepted: 01/30/2023] [Indexed: 02/17/2023]
Abstract
BACKGROUND Co-cultures and cell immobilization have been used for retaining biomass in a bioreactor, with the aim to improve the volumetric hydrogen productivity (QH2). Caldicellulosiruptor kronotskyensis is a strong cellulolytic species that possesses tāpirin proteins for attaching on lignocellulosic materials. C. owensensis has its reputation as a biofilm former. It was investigated whether continuous co-cultures of these two species with different types of carriers can improve the QH2. RESULTS QH2 up to 30 ± 0.2 mmol L-1 h-1 was obtained during pure culture of C. kronotskyensis with combined acrylic fibres and chitosan. In addition, the yield of hydrogen was 2.95 ± 0.1 mol H2 mol-1 sugars at a dilution rate (D) of 0.3 h-1. However, the second-best QH2 26.4 ± 1.9 mmol L-1 h-1 and 25.4 ± 0.6 mmol L-1 h-1 were obtained with a co-culture of C. kronotskyensis and C. owensensis with acrylic fibres only and a pure culture of C. kronotskyensis with acrylic fibres, respectively. Interestingly, the population dynamics revealed that C. kronotskyensis was the dominant species in the biofilm fraction, whereas C. owensensis was the dominant species in the planktonic phase. The highest amount of c-di-GMP (260 ± 27.3 µM at a D of 0.2 h-1) were found with the co-culture of C. kronotskyensis and C. owensensis without a carrier. This could be due to Caldicellulosiruptor producing c-di-GMP as a second messenger for regulation of the biofilms under the high dilution rate (D) to prevent washout. CONCLUSIONS The cell immobilization strategy using a combination of carriers exhibited a promising approach to enhance the QH2. The QH2 obtained during the continuous culture of C. kronotskyensis with combined acrylic fibres and chitosan gave the highest QH2 among the pure culture and mixed cultures of Caldicellulosiruptor in the current study. Moreover, it was the highest QH2 among all cultures of Caldicellulosiruptor species studied so far.
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Affiliation(s)
- Thitiwut Vongkampang
- Department of Applied Microbiology, Lund University, 124, 221 00, Lund, Sweden. .,Biorefinery and Functional Food Research Unit, Department of Biotechnology, Faculty of Technology, Mahasarakham University, Kantharawichai, Mahasarakham, 44150, Thailand.
| | - Krishnan Sreenivas
- grid.4514.40000 0001 0930 2361Department of Applied Microbiology, Lund University, 124, 221 00 Lund, Sweden
| | - Carl Grey
- grid.4514.40000 0001 0930 2361Department of Biotechnology, Lund University, 124, 221 00 Lund, Sweden
| | - Ed W. J. van Niel
- grid.4514.40000 0001 0930 2361Department of Applied Microbiology, Lund University, 124, 221 00 Lund, Sweden
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Rao NS, Ermann Lundberg L, Tomasson J, Tullberg C, Brink DP, Palmkron SB, van Niel EWJ, Håkansson S, Carlquist M. Non-inhibitory levels of oxygen during cultivation increase freeze-drying stress tolerance in Limosilactobacillus reuteri DSM 17938. Front Microbiol 2023; 14:1152389. [PMID: 37125176 PMCID: PMC10140318 DOI: 10.3389/fmicb.2023.1152389] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2023] [Accepted: 03/22/2023] [Indexed: 05/02/2023] Open
Abstract
The physiological effects of oxygen on Limosilactobacillus reuteri DSM 17938 during cultivation and the ensuing properties of the freeze-dried probiotic product was investigated. On-line flow cytometry and k-means clustering gating was used to follow growth and viability in real time during cultivation. The bacterium tolerated aeration at 500 mL/min, with a growth rate of 0.74 ± 0.13 h-1 which demonstrated that low levels of oxygen did not influence the growth kinetics of the bacterium. Modulation of the redox metabolism was, however, seen already at non-inhibitory oxygen levels by 1.5-fold higher production of acetate and 1.5-fold lower ethanol production. A significantly higher survival rate in the freeze-dried product was observed for cells cultivated in presence of oxygen compared to absence of oxygen (61.8% ± 2.4% vs. 11.5% ± 4.3%), coinciding with a higher degree of unsaturated fatty acids (UFA:SFA ratio of 10 for air sparged vs. 3.59 for N2 sparged conditions.). Oxygen also resulted in improved bile tolerance and boosted 5'nucleotidase activity (370 U/L vs. 240 U/L in N2 sparged conditions) but lower tolerance to acidic conditions compared bacteria grown under complete anaerobic conditions which survived up to 90 min of exposure at pH 2. Overall, our results indicate the controlled supply of oxygen during production may be used as means for probiotic activity optimization of L. reuteri DSM 17938.
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Affiliation(s)
- Nikhil Seshagiri Rao
- Division of Applied Microbiology, Department of Chemistry, Lund University, Lund, Sweden
- *Correspondence: Nikhil Seshagiri Rao,
| | - Ludwig Ermann Lundberg
- The Department of Molecular Sciences, Uppsala BioCenter, Swedish University of Agricultural Sciences, Uppsala, Sweden
- BioGaia, SE-103 64, Stockholm, Sweden
| | | | - Cecilia Tullberg
- Division of Biotechnology, Department of Chemistry, Lund University, Lund, Sweden
| | - Daniel P. Brink
- Division of Applied Microbiology, Department of Chemistry, Lund University, Lund, Sweden
| | - Shuai Bai Palmkron
- Department of Food Technology, Engineering and Nutrition, Department of Chemistry, Lund University, Lund, Sweden
| | - Ed W. J. van Niel
- Division of Applied Microbiology, Department of Chemistry, Lund University, Lund, Sweden
| | - Sebastian Håkansson
- Division of Applied Microbiology, Department of Chemistry, Lund University, Lund, Sweden
- BioGaia, SE-241 38, Eslöv, Sweden
| | - Magnus Carlquist
- Division of Applied Microbiology, Department of Chemistry, Lund University, Lund, Sweden
- Magnus Carlquist,
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Byrne E, Björkmalm J, Bostick JP, Sreenivas K, Willquist K, van Niel EWJ. Characterization and adaptation of Caldicellulosiruptor strains to higher sugar concentrations, targeting enhanced hydrogen production from lignocellulosic hydrolysates. Biotechnol Biofuels 2021; 14:210. [PMID: 34717729 PMCID: PMC8557575 DOI: 10.1186/s13068-021-02058-x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/23/2020] [Accepted: 10/17/2021] [Indexed: 06/13/2023]
Abstract
BACKGROUND The members of the genus Caldicellulosiruptor have the potential for future integration into a biorefinery system due to their capacity to generate hydrogen close to the theoretical limit of 4 mol H2/mol hexose, use a wide range of sugars and can grow on numerous lignocellulose hydrolysates. However, members of this genus are unable to survive in high sugar concentrations, limiting their ability to grow on more concentrated hydrolysates, thus impeding their industrial applicability. In this study five members of this genus, C. owensensis, C. kronotskyensis, C. bescii, C. acetigenus and C. kristjanssonii, were developed to tolerate higher sugar concentrations through an adaptive laboratory evolution (ALE) process. The developed mixed population C. owensensis CO80 was further studied and accompanied by the development of a kinetic model based on Monod kinetics to quantitatively compare it with the parental strain. RESULTS Mixed populations of Caldicellulosiruptor tolerant to higher glucose concentrations were obtained with C. owensensis adapted to grow up to 80 g/L glucose; other strains in particular C. kristjanssonii demonstrated a greater restriction to adaptation. The C. owensensis CO80 mixed population was further studied and demonstrated the ability to grow in glucose concentrations up to 80 g/L glucose, but with reduced volumetric hydrogen productivities ([Formula: see text]) and incomplete sugar conversion at elevated glucose concentrations. In addition, the carbon yield decreased with elevated concentrations of glucose. The ability of the mixed population C. owensensis CO80 to grow in high glucose concentrations was further described with a kinetic growth model, which revealed that the critical sugar concentration of the cells increased fourfold when cultivated at higher concentrations. When co-cultured with the adapted C. saccharolyticus G5 mixed culture at a hydraulic retention time (HRT) of 20 h, C. owensensis constituted only 0.09-1.58% of the population in suspension. CONCLUSIONS The adaptation of members of the Caldicellulosiruptor genus to higher sugar concentrations established that the ability to develop improved strains via ALE is species dependent, with C. owensensis adapted to grow on 80 g/L, whereas C. kristjanssonii could only be adapted to 30 g/L glucose. Although C. owensensis CO80 was adapted to a higher sugar concentration, this mixed population demonstrated reduced [Formula: see text] with elevated glucose concentrations. This would indicate that while ALE permits adaptation to elevated sugar concentrations, this approach does not result in improved fermentation performances at these higher sugar concentrations. Moreover, the observation that planktonic mixed culture of CO80 was outcompeted by an adapted C. saccharolyticus, when co-cultivated in continuous mode, indicates that the robustness of CO80 mixed culture should be improved for industrial application.
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Affiliation(s)
- Eoin Byrne
- Division of Applied Microbiology, Lund University, PO Box 124, 221 00, Lund, Sweden
- Department of Food Biosciences, Teagasc Food Research Centre, Moorepark, Fermoy, Co. Cork, P61 C996, Ireland
| | - Johanna Björkmalm
- Division of Applied Microbiology, Lund University, PO Box 124, 221 00, Lund, Sweden
- RISE, Ideon Science Park, Building Beta 2 3v Scheelevägen 17, 22370, Lund, Sweden
| | - James P Bostick
- Division of Applied Microbiology, Lund University, PO Box 124, 221 00, Lund, Sweden
- Coriolis Pharma Research GmbH, Fraunhoferstrasse 18B, 82152, Planegg, Germany
| | - Krishnan Sreenivas
- Division of Applied Microbiology, Lund University, PO Box 124, 221 00, Lund, Sweden
| | - Karin Willquist
- RISE, Ideon Science Park, Building Beta 2 3v Scheelevägen 17, 22370, Lund, Sweden
| | - Ed W J van Niel
- Division of Applied Microbiology, Lund University, PO Box 124, 221 00, Lund, Sweden.
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Örn OE, Sacchetto S, van Niel EWJ, Hatti-Kaul R. Enhanced Protocatechuic Acid Production From Glucose Using Pseudomonas putida 3-Dehydroshikimate Dehydratase Expressed in a Phenylalanine-Overproducing Mutant of Escherichia coli. Front Bioeng Biotechnol 2021; 9:695704. [PMID: 34249890 PMCID: PMC8264583 DOI: 10.3389/fbioe.2021.695704] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2021] [Accepted: 05/31/2021] [Indexed: 11/28/2022] Open
Abstract
Protocatechuic acid (PCA) is a strong antioxidant and is also a potential platform for polymer building blocks like vanillic acid, vanillin, muconic acid, and adipic acid. This report presents a study on PCA production from glucose via the shikimate pathway precursor 3-dehydroshikimate by heterologous expression of a gene encoding 3-dehydroshikimate dehydratase in Escherichia coli. The phenylalanine overproducing E. coli strain, engineered to relieve the allosteric inhibition of 3-deoxy-7-phosphoheptulonate synthase by the aromatic amino acids, was shown to give a higher yield of PCA than the unmodified strain under aerobic conditions. Highest PCA yield of 18 mol% per mol glucose and concentration of 4.2 g/L was obtained at a productivity of 0.079 g/L/h during cultivation in fed-batch mode using a feed of glucose and ammonium salt. Acetate was formed as a major side-product indicating a shift to catabolic metabolism as a result of feedback inhibition of the enzymes including 3-dehydroshikimate dehydratase by PCA when reaching a critical concentration. Indirect measurement of proton motive force by flow cytometry revealed no membrane damage of the cells by PCA, which was thus ruled out as a cause for affecting PCA formation.
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Affiliation(s)
- Oliver Englund Örn
- Division of Biotechnology, Department of Chemistry, Center for Chemistry and Chemical Engineering, Lund University, Lund, Sweden
| | - Stefano Sacchetto
- Division of Biotechnology, Department of Chemistry, Center for Chemistry and Chemical Engineering, Lund University, Lund, Sweden
| | - Ed W J van Niel
- Division of Applied Microbiology, Department of Chemistry, Center for Chemistry & Chemical Engineering, Lund University, Lund, Sweden
| | - Rajni Hatti-Kaul
- Division of Biotechnology, Department of Chemistry, Center for Chemistry and Chemical Engineering, Lund University, Lund, Sweden
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Vongkampang T, Sreenivas K, Engvall J, Grey C, van Niel EWJ. Characterization of simultaneous uptake of xylose and glucose in Caldicellulosiruptor kronotskyensis for optimal hydrogen production. Biotechnol Biofuels 2021; 14:91. [PMID: 33832529 PMCID: PMC8034154 DOI: 10.1186/s13068-021-01938-6] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/18/2021] [Accepted: 03/22/2021] [Indexed: 06/12/2023]
Abstract
BACKGROUND Caldicellulosiruptor kronotskyensis has gained interest for its ability to grow on various lignocellulosic biomass. The aim of this study was to investigate the growth profiles of C. kronotskyensis in the presence of mixtures of glucose-xylose. Recently, we characterized a diauxic-like pattern for C. saccharolyticus on lignocellulosic sugar mixtures. In this study, we aimed to investigate further whether C. kronotskyensis has adapted to uptake glucose in the disaccharide form (cellobiose) rather than the monosaccharide (glucose). RESULTS Interestingly, growth of C. kronotskyensis on glucose and xylose mixtures did not display diauxic-like growth patterns. Closer investigation revealed that, in contrast to C. saccharolyticus, C. kronotskyensis does not possess a second uptake system for glucose. Both C. saccharolyticus and C. kronotskyensis share the characteristics of preferring xylose over glucose. Growth on xylose was twice as fast (μmax = 0.57 h-1) as on glucose (μmax = 0.28 h-1). A study of the sugar uptake was made with different glucose-xylose ratios to find a kinetic relationship between the two sugars for transport into the cell. High concentrations of glucose inhibited xylose uptake and vice versa. The inhibition constants were estimated to be KI,glu = 0.01 cmol L-1 and KI,xyl = 0.001 cmol L-1, hence glucose uptake was more severely inhibited by xylose uptake. Bioinformatics analysis could not exclude that C. kronotskyensis possesses more than one transporter for glucose. As a next step it was investigated whether glucose uptake by C. kronotskyensis improved in the form of cellobiose. Indeed, cellobiose is taken up faster than glucose; nevertheless, the growth rate on each sugar remained similar. CONCLUSIONS C. kronotskyensis possesses a xylose transporter that might take up glucose at an inferior rate even in the absence of xylose. Alternatively, glucose can be taken up in the form of cellobiose, but growth performance is still inferior to growth on xylose. Therefore, we propose that the catabolism of C. kronotskyensis has adapted more strongly to pentose rather than hexose, thereby having obtained a specific survival edge in thermophilic lignocellulosic degradation communities.
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Affiliation(s)
- Thitiwut Vongkampang
- Division of Applied Microbiology, Lund University, P.O. Box 124, 221 00, Lund, Sweden.
| | - Krishnan Sreenivas
- Division of Applied Microbiology, Lund University, P.O. Box 124, 221 00, Lund, Sweden
| | - Jonathan Engvall
- Division of Applied Microbiology, Lund University, P.O. Box 124, 221 00, Lund, Sweden
| | - Carl Grey
- Division of Biotechnology, Lund University, P.O. Box 124, 221 00, Lund, Sweden
| | - Ed W J van Niel
- Division of Applied Microbiology, Lund University, P.O. Box 124, 221 00, Lund, Sweden
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6
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Kristjansdottir T, Ron EYC, Molins-Delgado D, Fridjonsson OH, Turner C, Bjornsdottir SH, Gudmundsson S, van Niel EWJ, Karlsson EN, Hreggvidsson GO. Engineering the carotenoid biosynthetic pathway in Rhodothermus marinus for lycopene production. Metab Eng Commun 2020; 11:e00140. [PMID: 32793416 PMCID: PMC7414004 DOI: 10.1016/j.mec.2020.e00140] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2020] [Revised: 06/25/2020] [Accepted: 07/20/2020] [Indexed: 11/20/2022] Open
Abstract
Rhodothermus marinus has the potential to be well suited for biorefineries, as an aerobic thermophile that produces thermostable enzymes and is able to utilize polysaccharides from different 2nd and 3rd generation biomass. The bacterium produces valuable chemicals such as carotenoids. However, the native carotenoids are not established for industrial production and R. marinus needs to be genetically modified to produce higher value carotenoids. Here we genetically modified the carotenoid biosynthetic gene cluster resulting in three different mutants, most importantly the lycopene producing mutant TK-3 (ΔtrpBΔpurAΔcruFcrtB::trpBcrtBT.thermophilus). The genetic modifications and subsequent structural analysis of carotenoids helped clarify the carotenoid biosynthetic pathway in R. marinus. The nucleotide sequences encoding the enzymes phytoene synthase (CrtB) and the previously unidentified 1′,2′-hydratase (CruF) were found fused together and encoded by a single gene in R. marinus. Deleting only the cruF part of the gene did not result in an active CrtB enzyme. However, by deleting the entire gene and inserting the crtB gene from Thermus thermophilus, a mutant strain was obtained, producing lycopene as the sole carotenoid. The lycopene produced by TK-3 was quantified as 0.49 g/kg CDW (cell dry weight). Genetically engineered Rhodothermus marinus produces lycopene instead of native γ-carotenoids. A gene encoding 1′,2′-hydratase (cruF) was identified in the genome, fused with the gene encoding phytoene synthase (crtB). Marker-replacement of the cruF-crtB gene with the crtB from Thermus thermophilus resulted in the R. marinus mutant TK-3. The mutant strain TK-3 produced lycopene as the sole carotenoid (0.49 g/kg CDW).
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Affiliation(s)
- Thordis Kristjansdottir
- Matis, Vinlandsleid 12, 113 Reykjavik, Iceland.,University of Iceland, Department of Computer Science, School of Engineering and Natural Sciences, Dunhagi 5, 107 Reykjavik, Iceland
| | - Emanuel Y C Ron
- Lund University, Department of Chemistry, Division of Biotechnology, Box 124, 221 00, Lund, Sweden
| | - Daniel Molins-Delgado
- Lund University, Department of Chemistry, Centre for Analysis and Synthesis, Box 124, 221 00, Lund, Sweden
| | | | - Charlotta Turner
- Lund University, Department of Chemistry, Centre for Analysis and Synthesis, Box 124, 221 00, Lund, Sweden
| | - Snaedis H Bjornsdottir
- University of Iceland, Department of Biology, School of Engineering and Natural Sciences, Sturlugata 7, 102 Reykjavík, Iceland
| | - Steinn Gudmundsson
- University of Iceland, Department of Computer Science, School of Engineering and Natural Sciences, Dunhagi 5, 107 Reykjavik, Iceland
| | - Ed W J van Niel
- Lund University, Department of Chemistry, Division of Applied Microbiology, Box 124, 221 00, Lund, Sweden
| | - Eva Nordberg Karlsson
- Lund University, Department of Chemistry, Division of Biotechnology, Box 124, 221 00, Lund, Sweden
| | - Gudmundur O Hreggvidsson
- Matis, Vinlandsleid 12, 113 Reykjavik, Iceland.,University of Iceland, Department of Biology, School of Engineering and Natural Sciences, Sturlugata 7, 102 Reykjavík, Iceland
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Ron EYC, Sardari RRR, Anthony R, van Niel EWJ, Hreggvidsson GO, Nordberg-Karlsson E. Cultivation technology development of Rhodothermus marinus DSM 16675. Extremophiles 2019; 23:735-745. [PMID: 31522265 PMCID: PMC6801211 DOI: 10.1007/s00792-019-01129-0] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2019] [Accepted: 08/14/2019] [Indexed: 12/17/2022]
Abstract
This work presents an evaluation of batch, fed-batch, and sequential batch cultivation techniques for production of R. marinus DSM 16675 and its exopolysaccharides (EPSs) and carotenoids in a bioreactor, using lysogeny broth (LB) and marine broth (MB), respectively, in both cases supplemented with 10 g/L maltose. Batch cultivation using LB supplemented with maltose (LBmalt) resulted in higher cell density (OD620 = 6.6) than use of MBmalt (OD620 = 1.7). Sequential batch cultivation increased the cell density threefold (OD620 = 20) in LBmalt and eightfold (OD620 = 14) in MBmalt. In both single and sequential batches, the production of carotenoids and EPSs using LBmalt was detected in the exponential phase and stationary phase, respectively, while in MBmalt formation of both products was detectable in both the exponential and stationary phases of the culture. Heteropolymeric EPSs were produced with an overall volumetric productivity (QE) of 0.67 (mg/L h) in MBmalt and the polymer contained xylose. In LB, QE was lower (0.1 mg/L h) and xylose could not be detected in the composition of the produced EPSs. In conclusion, this study showed the importance of a process design and medium source for production of R. marinus DSM 16675 and its metabolites.
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Affiliation(s)
- Emanuel Y C Ron
- Division of Biotechnology, Department of Chemistry, Lund University, Naturvetarvägen 14, 22100, Lund, Sweden
| | - Roya R R Sardari
- Division of Biotechnology, Department of Chemistry, Lund University, Naturvetarvägen 14, 22100, Lund, Sweden.
| | - Richard Anthony
- Division of Biotechnology, Department of Chemistry, Lund University, Naturvetarvägen 14, 22100, Lund, Sweden
| | - Ed W J van Niel
- Division of Applied Microbiology, Department of Chemistry, Lund University, Naturvetarvägen 14, 22100, Lund, Sweden
| | | | - Eva Nordberg-Karlsson
- Division of Biotechnology, Department of Chemistry, Lund University, Naturvetarvägen 14, 22100, Lund, Sweden
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Hernández A, Larsson CU, Sawicki R, van Niel EWJ, Roos S, Håkansson S. Impact of the fermentation parameters pH and temperature on stress resilience of Lactobacillus reuteri DSM 17938. AMB Express 2019; 9:66. [PMID: 31102098 PMCID: PMC6525219 DOI: 10.1186/s13568-019-0789-2] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2019] [Accepted: 05/02/2019] [Indexed: 11/10/2022] Open
Abstract
This study was undertaken to investigate the impact of culture pH (4.5-6.5) and temperature (32-37 °C) on the stress resilience of Lactobacillus reuteri DSM 17938 during freeze-drying and post freeze-drying exposure to low pH (pH 2) and bile salts. Response-surface methodology analysis revealed that freeze-drying survival rates [Formula: see text] were linearly related to pH with the highest survival rate of 80% when cells were cultured at pH 6.5 and the lowest was 40% when cells were cultured at pH 4.5. The analysis further revealed that within the chosen temperature range the culture temperature did not significantly affect the freeze-drying survival rate. However, fermentation at pH 4.5 led to better survival rates when rehydrated cells were exposed to low pH shock or bile salts. Thus, the effect of pH on freeze-drying survival was in contrast to effects on low pH and bile salts stress tolerance. The rationale behind this irreconcilability is based on the responses being dissimilar and are not tuned to each other. Culturing strain DSM 17938 at pH values higher than 5.5 could be a useful option to improve the survivability and increase viable cell numbers in the final freeze-dried product. However, the dissimilar responses for the process- and application parameters tested here suggest that an optimal compromise has to be found in order to obtain the most functional probiotic product possible.
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Soto LR, Byrne E, van Niel EWJ, Sayed M, Villanueva CC, Hatti-Kaul R. Hydrogen and polyhydroxybutyrate production from wheat straw hydrolysate using Caldicellulosiruptor species and Ralstonia eutropha in a coupled process. Bioresour Technol 2019; 272:259-266. [PMID: 30352368 DOI: 10.1016/j.biortech.2018.09.142] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/28/2018] [Revised: 09/27/2018] [Accepted: 09/28/2018] [Indexed: 06/08/2023]
Abstract
This report presents an integrated biorefinery concept in which wheat straw hydrolysate was treated with co-cultures of osmotolerant thermophilic bacterial strains, Caldicellulosiruptor saccharolyticus and C. owensensis to obtain hydrogen, while the liquid effluent containing acetate and residual glucose was used as feed for polyhydroxybutyrate (PHB) production by Ralstonia eutropha. The Caldicellulosiruptor spp. co-culture consumed 10.8 g/L of pretreated straw sugars, glucose and xylose, producing 134 mmol H2/L. PHB accumulation by R. eutropha was first studied in minimal salts medium using acetate with/without glucose as carbon source. Addition of salts promoted cell growth and PHB production in the effluent. Fed-batch cultivation in a nitrogen limited medium with 40% (v/v) aeration resulted in a cell density of 15.1 g/L with PHB content of 80.1% w/w and PHB concentration of 12.1 g/L, while 20% aeration gave a cell density of 11.3 g/L with 83.4% w/w PHB content and 9.4 g/L PHB concentration.
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Affiliation(s)
- Luis Romero Soto
- Biotechnology, Department of Chemistry, Center for Chemistry & Chemical Engineering, Lund University, Box 124, SE-221 00 Lund, Sweden; Instituto de Investigación y Desarrollo de Procesos Químicos(3), Facultad de Ingeniería, Universidad Mayor de San Andrés, P.O. Box 12958, La Paz, Bolivia
| | - Eoin Byrne
- Applied Microbiology, Department of Chemistry, Center for Chemistry & Chemical Engineering, Lund University, Box 124, SE-221 00 Lund, Sweden
| | - Ed W J van Niel
- Applied Microbiology, Department of Chemistry, Center for Chemistry & Chemical Engineering, Lund University, Box 124, SE-221 00 Lund, Sweden
| | - Mahmoud Sayed
- Biotechnology, Department of Chemistry, Center for Chemistry & Chemical Engineering, Lund University, Box 124, SE-221 00 Lund, Sweden
| | - Cristhian Carrasco Villanueva
- Instituto de Investigación y Desarrollo de Procesos Químicos(3), Facultad de Ingeniería, Universidad Mayor de San Andrés, P.O. Box 12958, La Paz, Bolivia
| | - Rajni Hatti-Kaul
- Biotechnology, Department of Chemistry, Center for Chemistry & Chemical Engineering, Lund University, Box 124, SE-221 00 Lund, Sweden.
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Björkmalm J, Byrne E, van Niel EWJ, Willquist K. A non-linear model of hydrogen production by Caldicellulosiruptor saccharolyticus for diauxic-like consumption of lignocellulosic sugar mixtures. Biotechnol Biofuels 2018; 11:175. [PMID: 29977336 PMCID: PMC6013967 DOI: 10.1186/s13068-018-1171-3] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/24/2018] [Accepted: 06/12/2018] [Indexed: 06/08/2023]
Abstract
BACKGROUND Caldicellulosiruptor saccharolyticus is an attractive hydrogen producer suitable for growth on various lignocellulosic substrates. The aim of this study was to quantify uptake of pentose and hexose monosaccharides in an industrial substrate and to present a kinetic growth model of C. saccharolyticus that includes sugar uptake on defined and industrial media. The model is based on Monod and Hill kinetics extended with gas-to-liquid mass transfer and a cybernetic approach to describe diauxic-like growth. RESULTS Mathematical expressions were developed to describe hydrogen production by C. saccharolyticus consuming glucose, xylose, and arabinose. The model parameters were calibrated against batch fermentation data. The experimental data included four different cases: glucose, xylose, sugar mixture, and wheat straw hydrolysate (WSH) fermentations. The fermentations were performed without yeast extract. The substrate uptake rate of C. saccharolyticus on single sugar-defined media was higher on glucose compared to xylose. In contrast, in the defined sugar mixture and WSH, the pentoses were consumed faster than glucose. Subsequently, the cultures entered a lag phase when all pentoses were consumed after which glucose uptake rate increased. This phenomenon suggested a diauxic-like behavior as was deduced from the successive appearance of two peaks in the hydrogen and carbon dioxide productivity. The observation could be described with a modified diauxic model including a second enzyme system with a higher affinity for glucose being expressed when pentose saccharides are consumed. This behavior was more pronounced when WSH was used as substrate. CONCLUSIONS The previously observed co-consumption of glucose and pentoses with a preference for the latter was herein confirmed. However, once all pentoses were consumed, C. saccharolyticus most probably expressed another uptake system to account for the observed increased glucose uptake rate. This phenomenon could be quantitatively captured in a kinetic model of the entire diauxic-like growth process. Moreover, the observation indicates a regulation system that has fundamental research relevance, since pentose and glucose uptake in C. saccharolyticus has only been described with ABC transporters, whereas previously reported diauxic growth phenomena have been correlated mainly to PTS systems for sugar uptake.
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Affiliation(s)
- Johanna Björkmalm
- Department of Energy and Circular Economy, RISE Research Institutes of Sweden, PO Box 857, 501 15 Borås, Sweden
- Division of Applied Microbiology, Lund University, PO Box 124, 221 00 Lund, Sweden
| | - Eoin Byrne
- Division of Applied Microbiology, Lund University, PO Box 124, 221 00 Lund, Sweden
| | - Ed W. J. van Niel
- Division of Applied Microbiology, Lund University, PO Box 124, 221 00 Lund, Sweden
| | - Karin Willquist
- Department of Energy and Circular Economy, RISE Research Institutes of Sweden, PO Box 857, 501 15 Borås, Sweden
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11
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Byrne E, Kovacs K, van Niel EWJ, Willquist K, Svensson SE, Kreuger E. Reduced use of phosphorus and water in sequential dark fermentation and anaerobic digestion of wheat straw and the application of ensiled steam-pretreated lucerne as a macronutrient provider in anaerobic digestion. Biotechnol Biofuels 2018; 11:281. [PMID: 30337960 PMCID: PMC6180601 DOI: 10.1186/s13068-018-1280-z] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/19/2018] [Accepted: 10/04/2018] [Indexed: 05/14/2023]
Abstract
BACKGROUND Current EU directives demand increased use of renewable fuels in the transportation sector but restrict governmental support for production of biofuels produced from crops. The use of intercropped lucerne and wheat may comply with the directives. In the current study, the combination of ensiled lucerne (Medicago sativa L.) and wheat straw as substrate for hydrogen and methane production was investigated. Steam-pretreated and enzymatically hydrolysed wheat straw [WSH, 76% of total chemical oxygen demand (COD)] and ensiled lucerne (LH, 24% of total COD) were used for sequential hydrogen production through dark fermentation and methane production through anaerobic digestion and directly for anaerobic digestion. Synthetic co-cultures of extreme thermophilic Caldicellulosiruptor species adapted to elevated osmolalities were used for dark fermentation. RESULTS Based on 6 tested steam pretreatment conditions, 5 min at 200 °C was chosen for the ensiled lucerne. The same conditions as applied for wheat straw (10 min at 200 °C with 1% acetic acid) would give similar sugar yields. Volumetric hydrogen productivities of 6.7 and 4.3 mmol/L/h and hydrogen yields of 1.9 and 1.8 mol/mol hexose were observed using WSH and the combination of WSH and LH, respectively, which were relatively low compared to those of the wild-type strains. The combinations of WSH plus LH and the effluent from dark fermentation of WSH plus LH were efficiently converted to methane in anaerobic digestion with COD removal of 85-89% at organic loading rates of COD 5.4 and 8.5 g/L/day, respectively, in UASB reactors. The nutrients in the combined hydrolysates could support this conversion. CONCLUSIONS This study demonstrates the possibility of reducing the water addition to WSH by 26% and the phosphorus addition by 80% in dark fermentation with Caldicellulosiruptor species, compared to previous reports. WSH and combined WSH and LH were well tolerated by osmotolerant co-cultures. The yield was not significantly different when using defined media or hydrolysates with the same concentrations of sugars. However, the sugar concentration was negatively correlated with the hydrogen yield when comparing the results to previous reports. Hydrolysates and effluents from dark fermentation can be efficiently converted to methane. Lucerne can serve as macronutrient provider in anaerobic digestion. Intercropping with wheat is promising.
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Affiliation(s)
- Eoin Byrne
- Division of Applied Microbiology, Dept. of Chemistry, Lund University, PO Box 124, 221 00 Lund, Sweden
| | - Krisztina Kovacs
- Dept. of Chemical Engineering, Lund University, PO Box 124, 221 00 Lund, Sweden
| | - Ed W. J. van Niel
- Division of Applied Microbiology, Dept. of Chemistry, Lund University, PO Box 124, 221 00 Lund, Sweden
| | - Karin Willquist
- RISE, Forskningsbyn Ideon Scheelevägen 27, 223 70 Lund, Sweden
| | - Sven-Erik Svensson
- Dept. of Biosystems and Technology, Swedish University of Agricultural Sciences, PO Box 103, 230 53 Alnarp, Sweden
| | - Emma Kreuger
- Division of Biotechnology, Dept. of Chemistry, Lund University, PO Box 124, 221 00 Lund, Sweden
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12
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Ron EYC, Plaza M, Kristjansdottir T, Sardari RRR, Bjornsdottir SH, Gudmundsson S, Hreggvidsson GO, Turner C, van Niel EWJ, Nordberg-Karlsson E. Characterization of carotenoids in Rhodothermus marinus. Microbiologyopen 2017; 7. [PMID: 29045010 PMCID: PMC5822342 DOI: 10.1002/mbo3.536] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2017] [Revised: 08/10/2017] [Accepted: 08/18/2017] [Indexed: 11/13/2022] Open
Abstract
Rhodothermus marinus, a marine aerobic thermophile, was first isolated from an intertidal hot spring in Iceland. In recent years, the R. marinus strain PRI 493 has been genetically modified, which opens up possibilities for targeted metabolic engineering of the species, such as of the carotenoid biosynthetic pathway. In this study, the carotenoids of the R. marinus type‐strain DSM 4252T, strain DSM 4253, and strain PRI 493 were characterized. Bioreactor cultivations were used for pressurized liquid extraction and analyzed by ultra‐high performance supercritical fluid chromatography with diode array and quadropole time‐of‐flight mass spectrometry detection (UHPSFC‐DAD‐QTOF/MS). Salinixanthin, a carotenoid originally found in Salinibacter ruber and previously detected in strain DSM 4253, was identified in all three R. marinus strains, both in the hydroxylated and nonhydroxylated form. Furthermore, an additional and structurally distinct carotenoid was detected in the three strains. MS/MS fragmentation implied that the mass difference between salinixanthin and the novel carotenoid structure corresponded to the absence of a 4‐keto group on the ß‐ionone ring. The study confirmed the lack of carotenoids for the strain SB‐71 (ΔtrpBΔpurAcrtBI’::trpB) in which genes encoding two enzymes of the proposed pathway are partially deleted. Moreover, antioxidant capacity was detected in extracts of all the examined R. marinus strains and found to be 2–4 times lower for the knock‐out strain SB‐71. A gene cluster with 11 genes in two operons in the R. marinusDSM 4252T genome was identified and analyzed, in which several genes were matched with carotenoid biosynthetic pathway genes in other organisms.
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Affiliation(s)
- Emanuel Y C Ron
- Division of Biotechnology, Department of Chemistry, Lund University, Lund, Sweden
| | - Merichel Plaza
- Division of Centre for Analysis and Synthesis, Department of Chemistry, Lund University, Lund, Sweden
| | | | - Roya R R Sardari
- Division of Biotechnology, Department of Chemistry, Lund University, Lund, Sweden
| | | | | | | | - Charlotta Turner
- Division of Centre for Analysis and Synthesis, Department of Chemistry, Lund University, Lund, Sweden
| | - Ed W J van Niel
- Division of Applied Microbiology, Department of Chemistry, Lund University, Lund, Sweden
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13
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van Niel EWJ, Bergdahl B, Hahn-Hägerdal B. Close to the Edge: Growth Restrained by the NAD(P)H/ATP Formation Flux Ratio. Front Microbiol 2017; 8:1149. [PMID: 28690597 PMCID: PMC5479917 DOI: 10.3389/fmicb.2017.01149] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2017] [Accepted: 06/07/2017] [Indexed: 11/13/2022] Open
Abstract
Most fermentative microorganisms grow well-under anaerobic conditions managing a balanced redox and appropriate energy metabolism, but a few species do exist in which cells have to cope with inadequate energy recovery or capture and/or redox balancing. Two cases of these species, i.e., the metabolically engineered Saccharomyces cerevisiae enabling it to ferment xylose and Lactobacillus reuteri fermenting glucose via the phosphoketolase pathway, are here used to introduce a quantification parameter to capture what limits the growth rate of these microorganisms under anaerobic conditions. This dimensionless parameter, the cofactor formation flux ratio (RJ), is the ratio between the redox formation flux (JNADH+NADPH), and the energy carrier formation flux (JATP), which are mainly connected to the central carbon pathways. Data from metabolic flux analyses performed in previous and present studies were used to estimate the RJ-values. Even though both microorganisms possess different central pathways, a similar relationship between RJ and the specific growth rate (μ) was found. Furthermore, for both microorganisms external electron acceptors moderately reduced the RJ-value, thereby raising the μ accordingly. Based on the emerging profile of this relationship an interpretation is presented suggesting that this quantitative analysis can be applied beyond the two microbial species experimentally investigated in the current study to provide data for future targeted strain development strategies.
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Affiliation(s)
- Ed W J van Niel
- Division of Applied Microbiology, Lund UniversityLund, Sweden
| | - Basti Bergdahl
- Division of Applied Microbiology, Lund UniversityLund, Sweden
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14
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Narayanan V, Sànchez i Nogué V, van Niel EWJ, Gorwa-Grauslund MF. Adaptation to low pH and lignocellulosic inhibitors resulting in ethanolic fermentation and growth of Saccharomyces cerevisiae. AMB Express 2016; 6:59. [PMID: 27566648 PMCID: PMC5001960 DOI: 10.1186/s13568-016-0234-8] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2016] [Accepted: 08/18/2016] [Indexed: 01/12/2023] Open
Abstract
Lignocellulosic bioethanol from renewable feedstocks using Saccharomyces cerevisiae is a promising alternative to fossil fuels owing to environmental challenges. S. cerevisiae is frequently challenged by bacterial contamination and a combination of lignocellulosic inhibitors formed during the pre-treatment, in terms of growth, ethanol yield and productivity. We investigated the phenotypic robustness of a brewing yeast strain TMB3500 and its ability to adapt to low pH thereby preventing bacterial contamination along with lignocellulosic inhibitors by short-term adaptation and adaptive lab evolution (ALE). The short-term adaptation strategy was used to investigate the inherent ability of strain TMB3500 to activate a robust phenotype involving pre-culturing yeast cells in defined medium with lignocellulosic inhibitors at pH 5.0 until late exponential phase prior to inoculating them in defined media with the same inhibitor cocktail at pH 3.7. Adapted cells were able to grow aerobically, ferment anaerobically (glucose exhaustion by 19 ± 5 h to yield 0.45 ± 0.01 g ethanol g glucose(-1)) and portray significant detoxification of inhibitors at pH 3.7, when compared to non-adapted cells. ALE was performed to investigate whether a stable strain could be developed to grow and ferment at low pH with lignocellulosic inhibitors in a continuous suspension culture. Though a robust population was obtained after 3600 h with an ability to grow and ferment at pH 3.7 with inhibitors, inhibitor robustness was not stable as indicated by the characterisation of the evolved culture possibly due to phenotypic plasticity. With further research, this short-term adaptation and low pH strategy could be successfully applied in lignocellulosic ethanol plants to prevent bacterial contamination.
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Affiliation(s)
- Venkatachalam Narayanan
- Division of Applied Microbiology, Department of Chemistry, Lund University, P.O. Box 124, 221 00 Lund, Sweden
| | - Violeta Sànchez i Nogué
- National Bioenergy Center, National Renewable Energy Laboratory, 15013 Denver West Parkway, Golden, CO 80401 USA
| | - Ed W. J. van Niel
- Division of Applied Microbiology, Department of Chemistry, Lund University, P.O. Box 124, 221 00 Lund, Sweden
| | - Marie F. Gorwa-Grauslund
- Division of Applied Microbiology, Department of Chemistry, Lund University, P.O. Box 124, 221 00 Lund, Sweden
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15
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Abstract
Methane is produced usually from organic waste in a straightforward anaerobic digestion process. However, hydrogen production is technically more challenging as more stages are needed to convert all biomass to hydrogen because of thermodynamic constraints. Nevertheless, the benefit of hydrogen is that it can be produced, both biologically and thermochemically, in more than one way from either organic compounds or water. Research in biological hydrogen production is booming, as reflected by the myriad of recently published reviews on the topic. This overview is written from the perspective of how to transfer as much energy as possible from the feedstock into the gaseous products hydrogen, and to a lesser extent, methane. The status and remaining challenges of all the biological processes are concisely discussed.
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Affiliation(s)
- Ed W J van Niel
- Division of Applied Microbiology, Lund University, 124, 221 00, Lund, Sweden.
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16
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Pawar SS, van Niel EWJ. Evaluation of assimilatory sulphur metabolism in Caldicellulosiruptor saccharolyticus. Bioresour Technol 2014; 169:677-685. [PMID: 25108266 DOI: 10.1016/j.biortech.2014.07.059] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/01/2014] [Revised: 07/14/2014] [Accepted: 07/15/2014] [Indexed: 05/23/2023]
Abstract
Caldicellulosiruptor saccharolyticus has gained reputation as being among the best microorganisms to produce H2 due to possession of various appropriate features. The quest to develop an inexpensive cultivation medium led to determine a possible replacement of the expensive component cysteine, i.e. sulphate. C. saccharolyticus assimilated sulphate successfully in absence of a reducing agent without releasing hydrogen sulphide. A complete set of genes coding for enzymes required for sulphate assimilation were found in the majority of Caldicellulosiruptor species including C. saccharolyticus. C. saccharolyticus displayed indifferent physiological behaviour to source of sulphur when grown under favourable conditions in continuous cultures. Increasing the usual concentration of sulphur in the feed medium increased substrate conversion. Choice of sulphur source did not affect the tolerance of C. saccharolyticus to high partial pressures of H2. Thus, sulphate can be a principle sulphur source in an economically viable and more sustainable biohydrogen process using C. saccharolyticus.
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Affiliation(s)
- Sudhanshu S Pawar
- Division of Applied Microbiology, Lund University, P.O. Box 124, SE-221 00 Lund, Sweden.
| | - Ed W J van Niel
- Division of Applied Microbiology, Lund University, P.O. Box 124, SE-221 00 Lund, Sweden.
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17
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Bergdahl B, Gorwa-Grauslund MF, van Niel EWJ. Physiological effects of over-expressing compartment-specific components of the protein folding machinery in xylose-fermenting Saccharomyces cerevisiae. BMC Biotechnol 2014; 14:28. [PMID: 24758421 PMCID: PMC4021093 DOI: 10.1186/1472-6750-14-28] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2013] [Accepted: 04/11/2014] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Efficient utilization of both glucose and xylose is necessary for a competitive ethanol production from lignocellulosic materials. Although many advances have been made in the development of xylose-fermenting strains of Saccharomyces cerevisiae, the productivity remains much lower compared to glucose. Previous transcriptional analyses of recombinant xylose-fermenting strains have mainly focused on central carbon metabolism. Very little attention has been given to other fundamental cellular processes such as the folding of proteins. Analysis of previously measured transcript levels in a recombinant XR/XDH-strain showed a wide down-regulation of genes targeted by the unfolded protein response during xylose fermentation. Under anaerobic conditions the folding of proteins is directly connected with fumarate metabolism and requires two essential enzymes: FADH2-dependent fumarate reductase (FR) and Ero1p. In this study we tested whether these enzymes impair the protein folding process causing the very slow growth of recombinant yeast strains on xylose under anaerobic conditions. RESULTS Four strains over-expressing the cytosolic (FRD1) or mitochondrial (OSM1) FR genes and ERO1 in different combinations were constructed. The growth and fermentation performance was evaluated in defined medium as well as in a complex medium containing glucose and xylose. Over-expression of FRD1, alone or in combination with ERO1, did not have any significant effect on xylose fermentation in any medium used. Over-expression of OSM1, on the other hand, led to a diversion of carbon from glycerol to acetate and a decrease in growth rate by 39% in defined medium and by 25% in complex medium. Combined over-expression of OSM1 and ERO1 led to the same diversion of carbon from glycerol to acetate and had a stronger detrimental effect on the growth in complex medium. CONCLUSIONS Increasing the activities of the FR enzymes and Ero1p is not sufficient to increase the anaerobic growth on xylose. So additional components of the protein folding mechanism that were identified in transcription analysis of UPR related genes may also be limiting. This includes i) the transcription factor encoded by HAC1 ii) the activity of Pdi1p and iii) the requirement of free FAD during anaerobic growth.
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Affiliation(s)
- Basti Bergdahl
- Division of Applied Microbiology, Department of Chemistry, Lund University, P,O, Box 124, Lund SE-22100, Sweden.
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18
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Bergdahl B, Sandström AG, Borgström C, Boonyawan T, van Niel EWJ, Gorwa-Grauslund MF. Engineering yeast hexokinase 2 for improved tolerance toward xylose-induced inactivation. PLoS One 2013; 8:e75055. [PMID: 24040384 PMCID: PMC3765440 DOI: 10.1371/journal.pone.0075055] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2013] [Accepted: 08/05/2013] [Indexed: 11/21/2022] Open
Abstract
Hexokinase 2 (Hxk2p) from Saccharomyces cerevisiae is a bi-functional enzyme being both a catalyst and an important regulator in the glucose repression signal. In the presence of xylose Hxk2p is irreversibly inactivated through an autophosphorylation mechanism, affecting all functions. Consequently, the regulation of genes involved in sugar transport and fermentative metabolism is impaired. The aim of the study was to obtain new Hxk2p-variants, immune to the autophosphorylation, which potentially can restore the repressive capability closer to its nominal level. In this study we constructed the first condensed, rationally designed combinatorial library targeting the active-site in Hxk2p. We combined protein engineering and genetic engineering for efficient screening and identified a variant with Phe159 changed to tyrosine. This variant had 64% higher catalytic activity in the presence of xylose compared to the wild-type and is expected to be a key component for increasing the productivity of recombinant xylose-fermenting strains for bioethanol production from lignocellulosic feedstocks.
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Affiliation(s)
- Basti Bergdahl
- Division of Applied Microbiology, Department of Chemistry, Lund University, Lund, Sweden
- * E-mail:
| | - Anders G. Sandström
- Division of Applied Microbiology, Department of Chemistry, Lund University, Lund, Sweden
| | - Celina Borgström
- Division of Applied Microbiology, Department of Chemistry, Lund University, Lund, Sweden
| | - Tarinee Boonyawan
- Division of Applied Microbiology, Department of Chemistry, Lund University, Lund, Sweden
| | - Ed W. J. van Niel
- Division of Applied Microbiology, Department of Chemistry, Lund University, Lund, Sweden
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Abstract
Apart from being applied as an energy carrier, hydrogen is in increasing demand as a commodity. Currently, the majority of hydrogen (H2) is produced from fossil fuels, but from an environmental perspective, sustainable H2 production should be considered. One of the possible ways of hydrogen production is through fermentation, in particular, at elevated temperature, i.e. thermophilic biohydrogen production. This short review recapitulates the current status in thermophilic biohydrogen production through fermentation of commercially viable substrates produced from readily available renewable resources, such as agricultural residues. The route to commercially viable biohydrogen production is a multidisciplinary enterprise. Microbiological studies have pointed out certain desirable physiological characteristics in H2-producing microorganisms. More process-oriented research has identified best applicable reactor types and cultivation conditions. Techno-economic and life cycle analyses have identified key process bottlenecks with respect to economic feasibility and its environmental impact. The review has further identified current limitations and gaps in the knowledge, and also deliberates directions for future research and development of thermophilic biohydrogen production.
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Affiliation(s)
- Sudhanshu S Pawar
- Applied Microbiology, Lund University, Getingevägen 60, 222 41, Lund, Sweden.
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Zeidan AA, Rådström P, van Niel EWJ. Stable coexistence of two Caldicellulosiruptor species in a de novo constructed hydrogen-producing co-culture. Microb Cell Fact 2010; 9:102. [PMID: 21192828 PMCID: PMC3022713 DOI: 10.1186/1475-2859-9-102] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2010] [Accepted: 12/30/2010] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Mixed culture enrichments have been used frequently for biohydrogen production from different feedstock. In spite of the several advantages offered by those cultures, they suffer poor H2 yield. Constructing defined co-cultures of known H2 producers may offer a better performance than mixed-population enrichments, while overcoming some of the limitations of pure cultures based on synergies among the microorganisms involved. RESULTS The extreme thermophiles Caldicellulosiruptor saccharolyticus DSM 8903 and C. kristjanssonii DSM 12137 were combined in a co-culture for H2 production from glucose and xylose in a continuous-flow stirred tank reactor. The co-culture exhibited a remarkable stability over a period of 70 days under carbon-sufficient conditions, with both strains coexisting in the system at steady states of different dilution rates, as revealed by species-specific quantitative PCR assays. The two strains retained their ability to stably coexist in the reactor even when glucose was used as the sole growth-limiting substrate. Furthermore, H2 yields on glucose exceeded those of either organism alone under the same conditions, alluding to a synergistic effect of the two strains on H2 production. A maximum H2 yield of 3.7 mol (mol glucose)(-1) was obtained by the co-culture at a dilution rate of 0.06 h(-1); a higher yield than that reported for any mixed culture to date. A reproducible pattern of population dynamics was observed in the co-culture under both carbon and non-carbon limited conditions, with C. kristjanssonii outgrowing C. saccharolyticus during the batch start-up phase and prevailing at higher dilution rates. A basic continuous culture model assuming the ability of C. saccharolyticus to enhance the growth of C. kristjanssonii could mimic the pattern of population dynamics observed experimentally and provide clues to the nature of interaction between the two strains. As a proof, the cell-free growth supernatant of C. saccharolyticus was found able to enhance the growth of C. kristjanssonii in batch culture through shortening its lag phase and increasing its maximum biomass concentration by ca. 18%. CONCLUSIONS This study provides experimental evidence on the stable coexistence of two closely related organisms isolated from geographically-distant habitats under continuous operation conditions, with the production of H2 at high yields. An interspecies interaction is proposed as the reason behind the remarkable ability of the two Caldicellulosiruptor strains to coexist in the system rather than only competing for the growth-limiting substrate.
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Affiliation(s)
- Ahmad A Zeidan
- Applied Microbiology, Lund University, Getingevägen 60, SE-222 41 Lund, Sweden.
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Kostesha N, Willquist K, Emneus J, van Niel EWJ. Probing the redox metabolism in the strictly anaerobic, extremely thermophilic, hydrogen-producing Caldicellulosiruptor saccharolyticus using amperometry. Extremophiles 2010; 15:77-87. [PMID: 21132340 DOI: 10.1007/s00792-010-0341-4] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2010] [Accepted: 11/12/2010] [Indexed: 10/18/2022]
Abstract
Changes in the redox metabolism in the anaerobic, extremely thermophilic, hydrogen-forming bacterium Caldicellulosiruptor saccharolyticus were probed for the first time in vivo using mediated amperometry with ferricyanide as a thermotolerant external mediator. Clear differences in the intracellular electron flow were observed when cells were supplied with different carbon sources. A higher electrochemical response was detected when cells were supplied with xylose than with sucrose or glucose. Moreover, using the mediated electrochemical method, it was possible to detect differences in the electron flow between cells harvested in the exponential and stationary growth phases. The electron flow of C. saccharolyticus was dependent on the NADH- and reduced ferredoxin generation flux and the competitive behavior of cytosolic and membrane-associated oxidoreductases. Sodium oxamate was used to inhibit the NADH-dependent lactate dehydrogenase, upon which more NADH was directed to membrane-associated enzymes for ferricyanide reduction, leading to a higher electrochemical signal. The method is noninvasive and the results presented here demonstrate that this method can be used to accurately detect changes in the intracellular electron flow and to probe redox enzyme properties of a strictly anaerobic thermophile in vivo.
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Affiliation(s)
- Natalie Kostesha
- Department of Micro- and Nanotechnology, Technical University of Denmark, Ørsteds Plads 345 East, 2800 Kgs. Lyngby, Denmark.
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Bielen AAM, Willquist K, Engman J, van der Oost J, van Niel EWJ, Kengen SWM. Pyrophosphate as a central energy carrier in the hydrogen-producing extremely thermophilic Caldicellulosiruptor saccharolyticus. FEMS Microbiol Lett 2010; 307:48-54. [PMID: 20557574 DOI: 10.1111/j.1574-6968.2010.01957.x] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
The role of inorganic pyrophosphate (PPi) as an energy carrier in the central metabolism of the extremely thermophilic bacterium Caldicellulosiruptor saccharolyticus was investigated. In agreement with its annotated genome sequence, cell extracts were shown to exhibit PPi-dependent phosphofructokinase and pyruvate phosphate dikinase activity. In addition, membrane-bound pyrophosphatase activity was demonstrated, while no significant cytosolic pyrophosphatase activity was detected. During the exponential growth phase, high PPi levels (approximately 4 +/- 2 mM) and relatively low ATP levels (0.43 +/- 0.07 mM) were found, and the PPi/ATP ratio decreased 13-fold when the cells entered the stationary phase. Pyruvate kinase activity appeared to be allosterically affected by PPi. Altogether, these findings suggest an important role for PPi in the central energy metabolism of C. saccharolyticus.
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Cao R, Zeidan AA, Rådström P, van Niel EWJ. Inhibition kinetics of catabolic dehydrogenases by elevated moieties of ATP and ADP--implication for a new regulation mechanism in Lactococcus lactis. FEBS J 2010; 277:1843-52. [PMID: 20193044 DOI: 10.1111/j.1742-4658.2010.07601.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
ATP and ADP inhibit, in varying degrees, several dehydrogenases of the central carbon metabolism of Lactococcus lactis ATCC 19435 in vitro, i.e. glyceraldehyde-3-phosphate dehydrogenase (GAPDH), lactate dehydrogenase (LDH) and alcohol dehydrogenase (ADH). Here we demonstrate mixed inhibition for GAPDH and competitive inhibition for LDH and ADH by adenine nucleotides in single inhibition studies. The nonlinear negative co-operativity was best modelled with Hill-type kinetics, showing greater flexibility than the usual parabolic inhibition equation. Because these natural inhibitors are present simultaneously in the cytoplasm, multiple inhibition kinetics was determined for each dehydrogenase. For ADH and LDH, the inhibitor combinations ATP plus NAD and ADP plus NAD are indifferent to each other. Model discrimination suggested that the weak allosteric inhibition of GAPDH had no relevance when multiple inhibitors are present. Interestingly, with ADH and GAPDH the combination of ATP and ADP exhibits lower dissociation constants than with either inhibitor alone. Moreover, the concerted inhibition of ADH and GAPDH, but not of LDH, shows synergy between the two nucleotides. Similar kinetics, but without synergies, were found for horse liver and yeast ADHs, indicating that dehydrogenases can be modulated by these nucleotides in a nonlinear manner in many organisms. The action of an elevated pool of ATP and ADP may effectively inactivate lactococcal ADH, but not GAPDH and LDH, providing leverage for the observed metabolic shift to homolactic acid formation in lactococcal resting cells on maltose. Therefore, we interpret these results as a regulation mechanism contributing to readjusting the flux of ATP production in L. lactis.
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Affiliation(s)
- Rong Cao
- Department of Applied Microbiology, Lund University, Lund, Sweden
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Willquist K, van Niel EWJ. Lactate formation in Caldicellulosiruptor saccharolyticus is regulated by the energy carriers pyrophosphate and ATP. Metab Eng 2010; 12:282-90. [PMID: 20060925 DOI: 10.1016/j.ymben.2010.01.001] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2009] [Revised: 12/16/2009] [Accepted: 01/04/2010] [Indexed: 11/17/2022]
Abstract
Caldicellulosiruptor saccharolyticus displays superior H(2) yields on a wide range of carbon sources provided that lactate formation is avoided. Nevertheless, a low lactate flux is initiated as the growth rate declined in the transition to the stationary phase, which coincides with a drastic decrease in the glucose consumption and acetate production fluxes. In addition, the decrease in growth rate was accompanied by a sudden increase and then decrease in NADH levels. The V'(MAX) of the lactate dehydrogenase (LDH) doubled when the cells entered the stationary phase. Kinetic analysis revealed that at the metabolic level LDH activity is regulated through (i) competitive inhibition by pyrophosphate (PPi, k(i)=1.7 mM) and NAD (k(i)=0.43 mM) and (ii) allosteric activation by FBP (300%), ATP (160%) and ADP (140%). From these data a MWC-based model was derived. Simulations with this model could explain the observed lactate shift by displaying how the sensitivity of LDH activity to NADH/NAD ratio varied with different PP(i) concentrations. Moreover, the activation of LDH by ATP indicates that C. saccharolyticus uses LDH as a means to adjusts its flux of ATP and NADH production. To our knowledge, this is the first time PPi is observed as an effector of LDH.
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Affiliation(s)
- Karin Willquist
- Applied Microbiology, Lund University, P.O. Box 124, 22100 Lund, Sweden
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Arsköld E, Svensson M, Grage H, Roos S, Rådström P, van Niel EWJ. Environmental influences on exopolysaccharide formation in Lactobacillus reuteri ATCC 55730. Int J Food Microbiol 2007; 116:159-67. [PMID: 17316859 DOI: 10.1016/j.ijfoodmicro.2006.12.010] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2006] [Revised: 12/21/2006] [Accepted: 12/22/2006] [Indexed: 10/23/2022]
Abstract
Lactobacillus reuteri is known to produce exopolysaccharides (EPS), which have the potential to be used as an alternative biothickener in the food industry. In this study, the effect of several environmental conditions on the growth and EPS production in the L. reuteri strain ATCC 55730 was determined. The expression of the corresponding reuteransucrase gene, gtfO, was investigated over time and the results indicated that the expression increased with growth during the exponential phase and subsequently decreased in the stationary phase. Fermentation with glucose and/or sucrose as carbon and energy source revealed that gtfO was constitutively expressed and that the activity profile was independent of the sugar source. In the applied ranges of parameter values, temperature and pH were the most important factors for EPS formation and only temperature for growth. The best EPS yield, 1.4 g g(-1) CDW, was obtained at the conditions 37 degrees C, pH 4.5 and 100 g l(-1) sucrose, which were close to the estimated optimal conditions: pH 4.56 and 100 g l(-1) sucrose. No EPS formation could be detected with glucose. In addition, no direct connection between the expression and the activity of reuteransucrase could be established. Finally, the strain ATCC 55730 was benchmarked against 14 other L. reuteri strains with respect to EPS production from sucrose and abilities to metabolise sucrose, glucose and fructose. Eight strains were able to produce glucan and a corresponding glucansucrase gene was confirmed for each of them.
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Affiliation(s)
- Emma Arsköld
- Applied Microbiology, Lund University, P.O. Box 124, SE-221 00 Lund, Sweden
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Abstract
Lactococcal lactate dehydrogenases (LDHs) are coregulated at the substrate level by at least two mechanisms: the fructose-1,6-biphosphate/phosphate ratio and the NADH/NAD ratio. Among the Lactococcus lactis species, there are strains that are predominantly regulated by the first mechanism (e.g., strain 65.1) or by the second mechanism (e.g., strain NCDO 2118). A more complete model of the kinetics of the regulation of lactococcal LDH is discussed.
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Affiliation(s)
- Ed W J van Niel
- Department of Applied Microbiology, Lund University, Lund SE-221 00, Sweden.
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van Niel EWJ, Claassen PAM, Stams AJM. Substrate and product inhibition of hydrogen production by the extreme thermophile, Caldicellulosiruptor saccharolyticus. Biotechnol Bioeng 2003; 81:255-62. [PMID: 12474247 DOI: 10.1002/bit.10463] [Citation(s) in RCA: 242] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Substrate and product inhibition of hydrogen production during sucrose fermentation by the extremely thermophilic bacterium Caldicellulosiruptor saccharolyticus was studied. The inhibition kinetics were analyzed with a noncompetitive, nonlinear inhibition model. Hydrogen was the most severe inhibitor when allowed to accumulate in the culture. Concentrations of 5-10 mM H(2) in the gas phase (identical with partial hydrogen pressure (pH(2)) of (1-2) x 10(4) Pa) initiated a metabolic shift to lactate formation. The extent of inhibition by hydrogen was dependent on the density of the culture. The highest tolerance for hydrogen was found at low volumetric hydrogen production rates, as occurred in cultures with low cell densities. Under those conditions the critical hydrogen concentration in the gas phase was 27.7 mM H(2) (identical with pH(2) of 5.6 x 10(4) Pa); above this value hydrogen production ceased completely. With an efficient removal of hydrogen sucrose fermentation was mainly inhibited by sodium acetate. The critical concentrations of sucrose and acetate, at which growth and hydrogen production was completely inhibited (at neutral pH and 70 degrees C), were 292 and 365 mM, respectively. Inorganic salts, such as sodium chloride, mimicked the effect of sodium acetate, implying that ionic strength was responsible for inhibition. Undissociated acetate did not contribute to inhibition of cultures at neutral or slightly acidic pH. Exposure of exponentially growing cultures to concentrations of sodium acetate or sodium chloride higher than ca. 175 mM caused cell lysis, probably due to activation of autolysins.
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Affiliation(s)
- Ed W J van Niel
- Laboratory for Microbiology, Wageningen University and Research Center, Hesselink van Suchtelenweg 4, 6703 CT Wageningen, The Netherlands.
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van Niel EWJ, Hofvendahl K, Hahn-Hägerdal B. Formation and conversion of oxygen metabolites by Lactococcus lactis subsp. lactis ATCC 19435 under different growth conditions. Appl Environ Microbiol 2002; 68:4350-6. [PMID: 12200286 PMCID: PMC124107 DOI: 10.1128/aem.68.9.4350-4356.2002] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
A semidefined medium based on Casamino Acids allowed Lactococcus lactis ATCC 19435 to grow in the presence of oxygen at a slow rate (0.015 h(-1)). Accumulation of H(2)O(2) in the culture prevented a higher growth rate. Addition of asparagine to the medium increased the growth rate, whereby H(2)O(2) accumulated only temporarily during the lag phase. H(2)O(2) is an inhibitor for several glycolytic enzymes, glyceraldehyde-3-phosphate dehydrogenase being the most sensitive. Strain ATCC 19435 contained NADH oxidase (maximum specific rate under aerobic conditions, 426 nmol of NADH min(-1) mg of protein(-1)), which reduced oxygen to water, whereby superoxide was formed as a by-product. H(2)O(2) originated from the dismutation of superoxide by superoxide dismutase. Although H(2)O(2) was rapidly destroyed under high metabolic fluxes, neither NADH peroxidase nor any other enzymatic H(2)O(2)-reducing activity was detected. However, pyruvate, the end product of glycolysis, reacted nonenzymatically and rapidly with H(2)O(2) and hence was a potential alternative for scavenging of this oxygen metabolite intracellularly. Indeed, intracellular concentrations of up to 93 mM pyruvate were detected in aerobic cultures growing at high rates. It is hypothesized that self-generated pyruvate may serve to protect L. lactis strain ATCC 19435 from H(2)O(2).
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Affiliation(s)
- Ed W J van Niel
- Department of Applied Microbiology, Lund University, SE-22100 Lund, Sweden.
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