Biotransformation of 5-hydroxymethylfurfural by Acinetobacter oleivorans S27 for the synthesis of furan derivatives

Enhanced upgrading of lignocellulosic substrates by coculture of Saccharomyces cerevisiae and Acinetobacter baylyi ADP1

BACKGROUND

Lignocellulosic biomass as feedstock has a huge potential for biochemical production. Still, efficient utilization of hydrolysates derived from lignocellulose is challenged by their complex and heterogeneous composition and the presence of inhibitory compounds, such as furan aldehydes. Using microbial consortia where two specialized microbes complement each other could serve as a potential approach to improve the efficiency of lignocellulosic biomass upgrading.

RESULTS

This study describes the simultaneous inhibitor detoxification and production of lactic acid and wax esters from a synthetic lignocellulosic hydrolysate by a defined coculture of engineered Saccharomyces cerevisiae and Acinetobacter baylyi ADP1. A. baylyi ADP1 showed efficient bioconversion of furan aldehydes present in the hydrolysate, namely furfural and 5-hydroxymethylfurfural, and did not compete for substrates with S. cerevisiae, highlighting its potential as a coculture partner. Furthermore, the remaining carbon sources and byproducts of S. cerevisiae were directed to wax ester production by A. baylyi ADP1. The lactic acid productivity of S. cerevisiae was improved approximately 1.5-fold (to 0.41 ± 0.08 g/L/h) in the coculture with A. baylyi ADP1, compared to a monoculture of S. cerevisiae.

CONCLUSION

The coculture of yeast and bacterium was shown to improve the consumption of lignocellulosic substrates and the productivity of lactic acid from a synthetic lignocellulosic hydrolysate. The high detoxification capacity and the ability to produce high-value products by A. baylyi ADP1 demonstrates the strain to be a potential candidate for coculture to increase production efficiency and economics of S. cerevisiae fermentations.

Advances in enzymatic conversion of biomass derived furfural and 5-hydroxymethylfurfural to value-added chemicals and solvents

The progress of versatile chemicals and bio-based fuels using renewable biomass has gained ample importance. Furfural and 5-hydroxymethylfurfural are biomass-derived compounds that serve as the cornerstone for high-value chemicals and have a myriad of industrial applications. Despite the significant research into several chemical processes for furanic platform chemicals conversion, the harsh reaction conditions and toxic by-products render their biological conversion an ideal alternative strategy. Although biological conversion confers an array of advantages, these processes have been reviewed less. This review explicates and evaluates notable improvements in the bioconversion of 5-hydroxymethylfurfural and furfural to comprehend the current developments in the biocatalytic transformation of furan. Enzymatic conversion of HMF and furfural to furanic derivative have been explored, while the latter has substantially overlooked a foretime. This discrepancy was reviewed along with the outlook on the potential usage of 5-hydroxymethylfurfural and furfural for the furan-based value-added products' synthesis.

Evaluating the potential of engineered Trichoderma atroviride and its laccase-mediated system for the efficient bioconversion of 5-hydroxymethylfufural

5-Hydroxymethylfurfural (HMF) is a fermentation inhibitor which is formed during acid-based thermochemical pre-treatment of biomass. The present study involves two approaches for HMF conversion; the first includes screening and identification of fungal strains which produce oxidoreductases for HMF bioconversion, and thereafter evaluating their roles in HMF conversion. Out of the ten fungal strains screened, genetically engineered Trichoderma atroviride (Lac⁺) showed maximum HMF bioconversion and the activities of ligninolytic enzymes produced were noted. Maximum HMF conversion of 99% was achieved at pH 5.0 and 30 °C when 72 h old 10% inoculum of T. atroviride (Lac⁺) was utilized for 6 days. Based on the fungal bioconversion of HMF to 2, 5 diformylfuran with 58% yield, laccase was observed to influence the conversion process. Thus, a comparative study was established on HMF conversion by 100 U/mL of commercial laccases and partially purified laccase from T. atroviride (Lac+). In the presence of TEMPO, T. atroviride laccase showed comparable HMF conversion to commercial laccases, which establishes the efficiency of fungi and ligninolytic enzymes in bioconversion of HMF to value-added products.

Rendered-Protein Hydrolysates as a Low-Cost Nitrogen Source for the Fungal Biotransformation of 5-Hydroxymethylfurfural

5-hydroxymethylfurfural (HMF) is a platform chemical that can be converted into a wide range of high-value derivatives. Industrially, HMF-based derivatives are synthesized via chemical catalysis. However, biocatalytic transformation has emerged as an attractive alternative. Significant advances have been made in the last years using isolated enzymes and whole-cell biocatalysts in HMF biotransformation. Nonetheless, one of the major bottlenecks is the cost of the process, mainly due to the microorganism growth substrate. In this work, biotransformation studies to transform HMF into 2,5-di(hydroxymethyl)furan (DHMF) were carried out with the fungus Fusarium striatum using low-cost protein hydrolysates. The protein hydrolysates were obtained from fines, an unexploited material produced during the rendering process of meat industry waste residues. Given the high content in the protein of fines, of around 46%, protein hydrolysis was optimized using two commercially available proteases, Alcalase 2.4 L and Neutrase 0.8 L. The maximum degree of hydrolysis (DH) achieved with Alcalase 2.4 L was 21.4% under optimal conditions of 5% E/S ratio, pH 8, 55 °C, and 24 h. On the other hand, Neutrase 0.8 L exhibited lower efficiency, and therefore, lower protein recovery. After optimization of the Neutrase 0.8 L process using the response surface methodology (RSM), the maximum DH achieved was 7.2% with the variables set at 15% E/S ratio, initial pH 8, 40 °C, and 10.5 h. Using these hydrolysates as a nitrogen source allowed higher sporulation of the fungus and, therefore, the use of a lower volume of inoculum (three-fold), obtaining a DHMF yield > 90%, 50% higher than the yield obtained when using commercial peptones. The presented process allows the transformation of animal co- and by-products into low-cost nitrogen sources, which greatly impacts the industrial feasibility of HMF biotransformation.

Current Advances in the Sustainable Conversion of 5-Hydroxymethylfurfural into 2,5-Furandicarboxylic Acid

2,5-Furandicarboxylic acid (FDCA) is currently considered one of the most relevant bio-sourced building blocks, representing a fully sustainable competitor for terephthalic acid as well as the main component in green polymers such as poly(ethylene 2,5-furandicarboxylate) (PEF). The oxidation of biobased 5-hydroxymethylfurfural (HMF) represents the most straightforward approach to obtain FDCA, thus attracting the attention of both academia and industries, as testified by Avantium with the creation of a new plant expected to produce 5000 tons per year. Several approaches allow the oxidation of HMF to FDCA. Metal-mediated homogeneous and heterogeneous catalysis, metal-free catalysis, electrochemical approaches, light-mediated procedures, as well as biocatalytic processes share the target to achieve FDCA in high yield and mild conditions. This Review aims to give an up-to-date overview of the current developments in the main synthetic pathways to obtain FDCA from HMF, with a specific focus on process sustainability.

Cold-adaptive traits identified by comparative genomic analysis of a lipase-producing Pseudomonas sp. HS6 isolated from snow-covered soil of Sikkim Himalaya and molecular simulation of lipase for wide substrate specificity

The genomic analysis of industrially important bacteria can help in understanding their capability to withstand extreme environments and shed light on their metabolic capabilities. The whole genome of a previously reported broad temperature active lipase-producing Pseudomonas sp. HS6, isolated from snow-covered soil of the Sikkim Himalayan Region, was analyzed to understand the capability of the bacterium to withstand cold temperatures and study its lipolytic nature. Pseudomonas sp. HS6 was found to be psychrotolerant with an optimal growth temperature ranging between 25 and 30 °C, with the ability to grow at 5 °C. The genome harbours various cold-adaptation genes, such as cold-shock proteins, fatty acid alteration, and cold stress-tolerance genes, supporting the psychrotolerant nature of the organism. The comparative analysis of Pseudomonas sp. HS6 genome showed the presence of amino acid substitutions in genes that favor efficient functioning and flexibility at cold temperatures. Genome mining revealed the presence of four triacylglycerol lipases, among which the putative lipase 3 was highly similar to the broad temperature-active lipase purified and characterized in our previous study. In silico studies of putative lipase 3 revealed broad substrate specificity with partial and no inhibition of the enzyme activity in the presence of PMSF and orlistat. The presence of genes associated with cold adaptations and true lipases with activity at broad temperature and substrate specificity in the genome of Pseudomonas sp. HS6 makes this bacterium a suitable candidate for industrial applications.

Biochemical biorefinery: A low-cost and non-waste concept for promoting sustainable circular bioeconomy

The transition from a fossil-based linear economy to a circular bioeconomy is no longer an option but rather imperative, given worldwide concerns about the depletion of fossil resources and the demand for innovative products that are ecocompatible. As a critical component of sustainable development, this discourse has attracted wide attention at the regional and international levels. Biorefinery is an indispensable technology to implement the blueprint of the circular bioeconomy. As a low-cost, non-waste innovative concept, the biorefinery concept will spur a myriad of new economic opportunities across a wide range of sectors. Consequently, scaling up biorefinery processes is of the essence. Despite several decades of research and development channeled into upscaling biorefinery processes, the commercialization of biorefinery technology appears unrealizable. In this review, challenges limiting the commercialization of biorefinery technologies are discussed, with a particular focus on biofuels, biochemicals, and biomaterials. To counteract these challenges, various process intensification strategies such as consolidated bioprocessing, integrated biorefinery configurations, the use of highly efficient bioreactors, simultaneous saccharification and fermentation, have been explored. This study also includes an overview of biomass pretreatment-generated inhibitory compounds as platform chemicals to produce other essential biocommodities. There is a detailed examination of the technological, economic, and environmental considerations of a sustainable biorefinery. Finally, the prospects for establishing a viable circular bioeconomy in Nigeria are briefly discussed.

Whole Cell Biocatalysis of 5-Hydroxymethylfurfural for Sustainable Biorefineries

The implementation of cost-effective and sustainable biorefineries to substitute the petroleum-based economy is dependent on coupling the production of bioenergy with high-value chemicals. For this purpose, the US Department of Energy identified a group of key target compounds to be produced from renewable biomass. Among them, 5-hydroxymethylfurfural (HMF) can be obtained by dehydration of the hexoses present in biomass and is an extremely versatile molecule that can be further converted into a wide range of higher value compounds. HMF derivatives include 2,5-bis(hydroxymethyl)furan (BHMF), 5-hydroxymethyl-furan-2-carboxylic acid (HMFCA), 2,5-diformylfuran (DFF), 5-formyl-2-furancarboxylic acid (FFCA) and 2,5-furandicarboxylic acid (FDCA), all presenting valuable applications, in polymers, bioplastics and pharmaceuticals. Biocatalysis conversion of HMF into its derivatives emerges as a green alternative, taking into account the high selectivity of enzymes and the mild reaction conditions used. Considering these factors, this work reviews the use of microorganisms as whole-cell biocatalysts for the production of HMF derivatives. In the last years, a large number of whole-cell biocatalysts have been discovered and developed for HMF conversion into BHMF, FDCA and HMFCA, however there are no reports on microbial production of DFF and FFCA. While the production of BHMF and HMFCA mainly relies on wild type microorganisms, FDCA production, which requires multiple bioconversion steps from HMF, is strongly dependent on genetic engineering strategies. Together, the information gathered supports the possibility for the development of cell factories to produce high-value compounds, envisioning economical viable biorefineries.

Metabolic engineering of Saccharomyces cerevisiae for the production of top value chemicals from biorefinery carbohydrates

The implementation of biorefineries for a cost-effective and sustainable production of energy and chemicals from renewable carbon sources plays a fundamental role in the transition to a circular economy. The US Department of Energy identified a group of key target compounds that can be produced from biorefinery carbohydrates. In 2010, this list was revised and included organic acids (lactic, succinic, levulinic and 3-hydroxypropionic acids), sugar alcohols (xylitol and sorbitol), furans and derivatives (hydroxymethylfurfural, furfural and furandicarboxylic acid), biohydrocarbons (isoprene), and glycerol and its derivatives. The use of substrates like lignocellulosic biomass that impose harsh culture conditions drives the quest for the selection of suitable robust microorganisms. The yeast Saccharomyces cerevisiae, widely utilized in industrial processes, has been extensively engineered to produce high-value chemicals. For its robustness, ease of handling, genetic toolbox and fitness in an industrial context, S. cerevisiae is an ideal platform for the founding of sustainable bioprocesses. Taking these into account, this review focuses on metabolic engineering strategies that have been applied to S. cerevisiae for converting renewable resources into the previously identified chemical targets. The heterogeneity of each chemical and its manufacturing process leads to inevitable differences between the development stages of each process. Currently, 8 of 11 of these top value chemicals have been already reported to be produced by recombinant S. cerevisiae. While some of them are still in an early proof-of-concept stage, others, like xylitol or lactic acid, are already being produced from lignocellulosic biomass. Furthermore, the constant advances in genome-editing tools, e.g. CRISPR/Cas9, coupled with the application of innovative process concepts such as consolidated bioprocessing, will contribute for the establishment of S. cerevisiae-based biorefineries.

Preparation of highly diffusible porous cross-linked lipase B from Candida antarctica conjugates: Advances in mass transfer and application in transesterification of 5-Hydroxymethylfurfural

The present work pronounces the three phase partitioning (TPP)-facilitated preparation of porous cross-linked Candida antarctica lipase B (CaLB) aggregates (pCLEAs) for 5-Hydroxymethylfurfural (HMF) esters synthesis. CLEAs and pCLEAs of CaLB were prepared with eupergit as the support under the optimized conditions of pH 8.0, eupergit/protein ratio of 3.0:1.0, 50 mM cross-linker concentration and 3.3 mg/mL BSA concentration in 4 h. The optimum starch concentration for pCLEAs was 0.20%, m/v. The maximum biocatalytic load was 650 U/g (CLEAs) and 721 U/g (pCLEAs), and the immobilized biocatalysts were stable over a pH range of 6.0-9.0 and temperature range of (40-60)°C. The BET surface area of CLEAs and pCLEAs were 21.3 and 29.1 m²/g, respectively, and the catalytic efficiency of pCLEAs was 2.2-fold higher than that of CLEAs. Subsequently, the pCLEAs of CaLB were utilized for the manufacturing of industrially significant HMF esters. Under the optimized transesterification conditions, HMF conversion with pCLEAs CaLB was 1.41- and 1.25-fold higher than with free and CLEAs CaLB, respectively. The pCLEAs were reused upto 8 consecutive transesterification cycles and the produced HMF esters reduced the surface tension of water from 72 mN/m to 32.6 mN/m, proving its potential application as surface-active compounds.

Bioengineering advancements, innovations and challenges on green synthesis of 2, 5-furan dicarboxylic acid

The major drawback of chemical transformations for the production of 2, 5-furan dicarboxylic acid (FDCA) implies the usage of hazardous chemicals, high temperature and high pressure from nonrenewable resources. Alternate to chemical methods, biological methods are promising. Microbial FDCA production is improved through engineering approaches of media conditions, homologous and heterologous expression of genes, genetic and metabolic engineering, etc. The highest FDCA production of 41.29 g/L is observed by an engineered Raultella ornitholytica BF 60 from 35 g/L HMF in sodium phosphate buffer with a 95.14% yield in 72 h. Also, an enzyme cascade system of recombinant and wild enzymes like periplasmic aldehyde oxidase ABC, galactose oxidase M3-5, HRP and catalase have transformed 6.3 g/L HMF to 7.81 g/L FDCA in phosphate buffer with 100% yield in 6 h. Still, these processes are emerging for fulfilling the industrial needs due to the challenges in 'green FDCA production'.

Securing a furan-based biorefinery: disclosing the genetic basis of the degradation of hydroxymethylfurfural and its derivatives in the model fungus Aspergillus nidulans

Hydroxymethylfurfural (HMF) is a promising lignocellulosic-derived source for the generation of diverse chemical building blocks constituting an alternative to fossil fuels. However, it remains unanswered if ubiquitous fungi can ensure their efficient decay, similar to that observed in highly specialised fungi. To disclose the genetic basis of HMF degradation in aspergilli, we performed a comprehensive analysis of Aspergillus nidulans ability to tolerate and to degrade HMF and its derivatives (including an HMF-dimer). We identified the degradation pathway using a suite of metabolomics methods and showed that HMF was modified throughout sequential reactions, ultimately yielding derivatives subsequently channelled to the TCA cycle. Based on the previously revealed hmfFGH gene cluster of Cupriavidus basilensis, we combined gene expression of homologous genes in Aspergillus nidulans and functional analyses in single-deletion mutants. Results were complemented with orthology analyses across the genomes of twenty-five fungal species. Our results support high functional redundancy for the initial steps of the HMF degradation pathway in the majority of the analysed fungal genomes and the assignment of a single-copy furan-2,5-dicarboxylic acid decarboxylase gene in A. nidulans. Collectively our data made apparent the superior capacity of aspergilli to mineralise HMF, furthering the environmental sustainability of a furan-based chemistry.

Redox-Switchable Biocatalyst for Controllable Oxidation or Reduction of 5-Hydroxymethylfurfural into High-Value Derivatives

Biocatalytic upgrading of biomass-derived 5-hydroxymethylfurfural (HMF) into high-value derivatives is of great significance in green chemistry. In this study, we disclosed the successful utilization of whole-cell Paraburkholderia azotifigens F18 for its switchable catalytic performance in the on-demand catalysis of HMF to different value-added derivatives, namely, selective reduction to 2,5-bis(hydroxymethyl)furan (BHMF) or oxidation to 5-hydroxymethyl-2-furancarboxylic acid (HMFCA). Based on the fine-tuning of biochemical properties, the biocatalyst can proceed an efficient hydrogenation reaction toward HMF with a good selectivity of 97.6% to yield the BHMF at 92.2%. Noteworthily, BHMF could be further oxidized to HMFCA and 2,5-furandicarboxylic acid (FDCA) by the whole cell. To realize the on-demand syntheses of HMFCA, the genes encoding HMF oxidoreductase/oxidase of whole-cell F18 were then deleted to prevent the further conversion of HMFCA to FDCA, which led to a 10-fold decrease of FDCA. Thus, an HMF conversion of 100% with an HMFCA yield of 98.3% was finally achieved by the engineered whole cell at a substrate concentration of 150 mM. Moreover, HMFCA synthesis was efficiently prepared with an excellent selectivity of 96.3% and a yield of 85.1% even at a high substrate concentration of up to 200 mM.

Production and characterisation of lipase for application in detergent industry from a novel Pseudomonas helmanticensis HS6

The aim of this study was to explore novel source of lipase from biodiversity hot spot region of Sikkim with activity at broad temperature range for application in detergent industry. Among the isolates, Pseudomonas helmanticensis HS6 showed activity at wide range of temperatures was selected for lipase production. Statistical optimisation for enhanced production of lipase resulted in enhancement of lipase activity from 2.3 to 179.3 U/mg. Lipase was purified resulting in 18.78 fold purification, 5.58% yield and high specific activity of 3368 U/mg. The partially purified lipase was found to be active in wide range of temperature (5-80 °C) and pH (6-9), showing optimum activity at 50 °C at pH 7. Peptide sequences on mass spectrometric analysis of purified lipase showed similarity to lipase family protein of three species of Pseudomonas. Both crude and purified lipase retained residual activity of 40-80% after 3 h of incubation with commercial detergents suggesting its application in detergent industry.

Production of biosurfactant by Bacillus subtilis RSL-2 isolated from sludge and biosurfactant mediated degradation of oil

This study aims to unveil the effect of biosurfactant as stimulant in crude oil bioremediation. Isolated oil-degrading strain, B. subtilis RSL 2 was optimized for the maximum oil degradation and biosurfactant production using Response surface methodology. The produced biosurfactant was characterized and investigated for its effect on microbial oil degradation in two modes (a) sequential and (b) simultaneous. The strain produced 3.5 g/L of biosurfactant at pH 4.0, 25 °C, using 1 g/L crude oil as the only C-source in 7 days, which was characterized as lipopeptide with a critical micelle concentration (CMC) of 0.5 g/L. The biosurfactant improved surface wettability of a hydrophobic substrate i.e. increased surface energy from 30 ± 1 to 35 ± 1 mJ/m². Further, the simultaneous feed of biosurfactant at 0.5 CMC enhanced oil biodegradation (72%) and biosurfactant production (5.2 g/L) by about 1.6 times than the sequential mode due to improvement in mobilization of oil thus making it more bioavailable.

Biotransformation of 5-hydroxymethylfurfural into 2,5-dihydroxymethylfuran by Ganoderma sessile and toxicological assessment of both compounds

Biotransformation has the advantages of low cost and environmental protection and is a preferred method for production of compounds. At present, most 2,5-dihydroxymethylfuran (DHMF) is synthesized by chemical methods. In this study, 12.008 μg/mL DHMF was produced from 9.045 μg/mL 5-hydroxymethylfurfural (5-HMF) with a yield of 1.33 g/g using the crude enzymes from fungus Ganoderma sessile. To elucidate the toxic potential for both compounds, cytotoxicity tests and acute toxicity were evaluated respectively. 5-HMF induced weak cytotoxicity in HCT-8, A549 and SGC-7901 cells and DHMF exerted no cytotoxicity on HCT-8 while induced inhibition proliferation of A549 and SGC-7901 cells. The acute toxicity study showed no mortality happened in any group even at the single dose of 2000 mg/kg body weight. These results suggest it is feasible to convert 5-HMF to DHMF via crude enzymes from fungus G. sessile under mild condition, and that DHMF displays a potential effect of antitumor in vitro with little acute toxicity.

Biocatalytic production of 2,5-furandicarboxylic acid: recent advances and future perspectives

2,5-Furandicarboxylic acid (FDCA) is attracting increasing attention because of its potential applications as a sustainable substitute to petroleum-derived terephthalic acid for the production of bio-based polymers, such as poly(ethylene 2,5-furandicarboxylate) (PEF). Many catalytic methods have been developed for the synthesis of FDCA, including chemocatalysis, biocatalysis, photocatalysis, and electrocatalysis. Biocatalysis is a promising approach with advantages that include mild reaction condition, lower cost, higher selectivity, and environment amity. However, the biocatalytic production of FDCA has hardly been reviewed. To fully understand the current research developments, this review comprehensively considers the research progress on toxic effects and biodegradation of furan aldehydes, and then summarizes the latest achievements concerning the synthesis of FDCA from 5-hydroxymethylfurfural and other chemicals, such as 2-furoic acid and 5-methoxymethylfurfural. Our primary focus is on biocatalytic methods, including enzymatic catalysis (in vitro) and whole-cell catalysis (in vivo). Furthermore, future research directions and general developmental trends for more efficient biocatalytic production of FDCA are also proposed.