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Catalysts
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Biocatalysis for Green Chemistry
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Biocatalysis for Green Chemistry

A special issue of Catalysts (ISSN 2073-4344). This special issue belongs to the section "Biocatalysis".

Deadline for manuscript submissions: closed (31 May 2021) | Viewed by 55195

Special Issue Editors

Dr. Zheng Guo

E-Mail Website
Guest Editor
Department of Engineering, Faculty of Technical Science, Aarhus University, 8000 Aarhus, Denmark
Interests: bio-refining; green synthesis; biocatalysts; enzyme engineering; lipid chemistry; ionic liquids; enzyme discovery; new chemistry
Dr. Bekir Engin Eser

E-Mail Website
Guest Editor
Department of Engineering, Faculty of Technical Sciences, Aarhus University, 8000, Aarhus, Denmark
Interests: biocatalysis; enzyme engineering; enzyme kinetics and mechanisms

Special Issue Information

Dear colleagues,

Using biocatalysts, namely, enzymes or whole-cells, to develop greener approaches for organic synthesis and for bio-based production has been the central focus of biocatalysis. Enzymes, which can be used in isolated/purified form or as whole-cell catalysts, possess great advantages over their chemical counterparts. They are able to catalyze many kinds of reactions that are not accessible by other catalysts. Enzymes exhibit high catalytic efficiencies and excellent chemo-, regio-, and stereo-selectivities under mild reaction conditions. Moreover, enzymes are biocompatible, biodegradable, and generate much less waste than chemical catalysts. Biocatalysis is also very well suited for sustainable production using inexpensive and abundant starting materials, such as biomass, to generate high-value products.

However, there are also challenges associated with use of biocatalysts for synthetic purposes. These include the poor stability of enzymes at non-conventional conditions (e.g., high temperature, high pressure, and organic solvents), the requirement for expensive cofactors or partner proteins, and inhibition by high substrate/product concentrations. Moreover, enzymes are not very effective towards non-natural substrates, which are desired starting materials or compounds for many synthetic purposes.

Thus, there is a continuous need for the development of enzymes and biocatalytic processes for green and sustainable synthesis. Recent advances in molecular biology, microbiology, and high-throughput screening methods render great opportunities to discover new enzymes and to engineer existing enzymes for generating biocatalysts that are well suited for a target synthetic route. In addition, progress in medium engineering, enzyme immobilization, cofactor regeneration systems, cascade reactions, and computational approaches for enzyme design hold great promise to overcome the bottlenecks. Overall, with the recent developments in the field, enzymes and enzymatic processes can be modified to achieve a desired synthesis in an efficient way.

In this Special Issue, we welcome original research articles and reviews focused on all aspects of biocatalysis in green synthesis, including, but not limited to, the following:

-Enzymatic synthesis of value-added chemicals (e.g., active pharmaceutical ingredients, food additives, biofuels, and biobased materials)

-Enzyme discovery, design, and engineering for natural and non-natural synthetic routes

-Enzymatic transformation from sustainable biomass

-Enzymatic and/or chemo-enzymatic cascade reactions

-Optimization of biocatalytic processes through medium engineering, cofactor regeneration, and enzyme immobilization

Prof. Dr. Zheng Guo
Dr. Bekir Engin Eser
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Catalysts is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2700 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • biocatalysis
  • green chemistry
  • organic synthesis
  • enzymatic kinetic resolution
  • cascade reactions
  • asymmetric synthesis
  • sustainable synthesis
  • enzyme discovery
  • enzyme engineering
  • directed evolution
  • cofactor regeneration
  • enzyme immobilization
  • machine learning in enzyme design

Published Papers (16 papers)

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14 pages, 1640 KiB  
Article
Evaluation of Cr(VI) Reduction Using Indigenous Bacterial Consortium Isolated from a Municipal Wastewater Sludge: Batch and Kinetic Studies
by Buyisile Kholisa, Mpumelelo Matsena and Evans M. N. Chirwa
Catalysts 2021, 11(9), 1100; https://0-doi-org.brum.beds.ac.uk/10.3390/catal11091100 - 13 Sep 2021
Cited by 9 | Viewed by 2506
Abstract
Hexavalent Chromium (Cr(VI)) has long been known to be highly mobile and toxic when compared with the other stable oxidation state, Cr(III). Cr(VI)-soluble environmental pollutants have been detected in soils and water bodies receiving industrial and agricultural waste. The reduction of Cr(VI) by [...] Read more.
Hexavalent Chromium (Cr(VI)) has long been known to be highly mobile and toxic when compared with the other stable oxidation state, Cr(III). Cr(VI)-soluble environmental pollutants have been detected in soils and water bodies receiving industrial and agricultural waste. The reduction of Cr(VI) by microbial organisms is considered to be an environmentally compatible, less expensive and sustainable remediation alternative when compared to conventional treatment methods, such as chemical neutralization and chemical precipitation of Cr. This study aims to isolate and identify the composition of the microbial consortium culture isolated from waste activated sludge and digested sludge from a local wastewater treatment plant receiving high loads of Cr(VI) from an abandoned chrome foundry in Brits (North Waste Province, South Africa). Furthermore, the Cr(VI) reduction capability and efficiency by the isolated bacteria were investigated under a range of operational conditions, i.e., pH, temperature and Cr(VI) loading. The culture showed great efficiency in reduction capability, with 100% removal in less than 4 h at a nominal loading concentration of 50 mg Cr(VI)/L. The culture showed resilience by achieving total removal at concentrations as high as 400 mg Cr(VI)/L. The consortia exhibited considerable Cr(VI) removal efficiency in the pH range from 2 to 11, with 100% removal being achieved at a pH value of 7 at a 37 ± 1 °C incubation temperature. The time course reduction data fitted well on both first and second-order exponential rate equation yielding first-order rate constants in the range 0.615 to 0.011 h−1 and second order rate constants 0.0532 to 5 × 10−5 L·mg−1·h−1 for Cr(VI) concentration of 50–400 mg/L. This study demonstrated the bacterial consortium from municipal wastewater sludge has a high tolerance and reduction ability over a wide range of experimental conditions. Thus, show promise that bacteria could be used for hexavalent chromium remediate in contaminated sites. Full article
(This article belongs to the Special Issue Biocatalysis for Green Chemistry)
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14 pages, 2432 KiB  
Article
Performance Evaluation of Selenite (SeO32−) Reduction by Enterococcus spp.
by Job T. Tendenedzai, Evans M. N. Chirwa and Hendrik G. Brink
Catalysts 2021, 11(9), 1024; https://0-doi-org.brum.beds.ac.uk/10.3390/catal11091024 - 24 Aug 2021
Cited by 8 | Viewed by 2130
Abstract
Lactic acid bacteria (LAB) such as Enterococcus spp. have an advantage over several bacteria because of their ability to easily adapt to extreme conditions which include high temperatures, highly acidic or alkaline conditions and toxic metals. Although many microorganisms have been shown to [...] Read more.
Lactic acid bacteria (LAB) such as Enterococcus spp. have an advantage over several bacteria because of their ability to easily adapt to extreme conditions which include high temperatures, highly acidic or alkaline conditions and toxic metals. Although many microorganisms have been shown to reduce selenite (SeO32−) to elemental selenium (Se0), not much work has been done on the combined effect of Enterococcus spp. In this study, aerobic batch reduction of different selenite concentrations (1, 3 and 5 mM) was conducted using Enterococcus hermanniensis sp. and Enterococcus gallinarum sp. (3.5 h, 35 ± 2 °C, starting pH > 8.5). Results from the experiments showed that the average reductions rates were 0.608, 1.921 and 3.238 mmol·(L·h)−1, for the 1, 3 and 5 mM SeO32− concentrations respectively. In addition, more selenite was reduced for the 5 mM concentration compared to the 1 and 3 mM concentrations albeit constant biomass being used for all experiments. Other parameters which were monitored were the glucose consumption rate, protein variation, pH and ORP (oxidation reduction potential). TEM analysis was also conducted and it showed the location of electron-dense selenium nanoparticles (SeNPs). From the results obtained in this study, the authors concluded that Enterococcus species’s high adaptability makes it suitable for rapid selenium reduction and biosynthesis of elemental selenium. Full article
(This article belongs to the Special Issue Biocatalysis for Green Chemistry)
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15 pages, 4222 KiB  
Article
Identifying Energy Extraction Optimisation Strategies of Actinobacillus succinogenes
by Waldo Gideon Lexow, Sekgetho Charles Mokwatlo, Hendrik Gideon Brink and Willie Nicol
Catalysts 2021, 11(8), 1016; https://0-doi-org.brum.beds.ac.uk/10.3390/catal11081016 - 23 Aug 2021
Cited by 4 | Viewed by 2172
Abstract
A. succinogenes is well known for utilising various catabolic pathways. A multitude of batch fermentation studies confirm flux shifts in the catabolism as time proceeds. It has also been shown that continuous cultures exhibit flux variation as a function of dilution rate. This [...] Read more.
A. succinogenes is well known for utilising various catabolic pathways. A multitude of batch fermentation studies confirm flux shifts in the catabolism as time proceeds. It has also been shown that continuous cultures exhibit flux variation as a function of dilution rate. This indicates a direct influence of the external environment on the proteome of the organism. In this work, ATP production efficiency was explored to evaluate the extent of bio-available energy on the production behaviour of A. succinogenes. It was found that the microbe successively utilised its most-to-least efficient energy extraction pathways, providing evidence of an energy optimisation survival strategy. Moreover, data from this study suggest a pyruvate overflow mechanism as a means to throttle acetic and formic acid production, indicating a scenario in which the external concentration of these acids play a role in the energy extraction capabilities of the organism. Data also indicates a fleeting regime where A. succinogenes utilises an oxidised environment to its advantage for ATP production. Here it is postulated that the energy gain and excretion cost of catabolites coupled to the changing environment is a likely mechanism responsible for the proteome alteration and its ensuing carbon flux variation. This offers valuable insights into the microbe’s metabolic logic gates, providing a foundation to understand how to exploit the system. Full article
(This article belongs to the Special Issue Biocatalysis for Green Chemistry)
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16 pages, 2606 KiB  
Article
Criteria for Engineering Cutinases: Bioinformatics Analysis of Catalophores
by Sara Fortuna, Marco Cespugli, Anamaria Todea, Alessandro Pellis and Lucia Gardossi
Catalysts 2021, 11(7), 784; https://0-doi-org.brum.beds.ac.uk/10.3390/catal11070784 - 28 Jun 2021
Cited by 2 | Viewed by 2137
Abstract
Cutinases are bacterial and fungal enzymes that catalyze the hydrolysis of natural cutin, a three-dimensional inter-esterified polyester with epoxy-hydroxy fatty acids with chain lengths between 16 and 18 carbon atoms. Due to their ability to accept long chain substrates, cutinases are also effective [...] Read more.
Cutinases are bacterial and fungal enzymes that catalyze the hydrolysis of natural cutin, a three-dimensional inter-esterified polyester with epoxy-hydroxy fatty acids with chain lengths between 16 and 18 carbon atoms. Due to their ability to accept long chain substrates, cutinases are also effective in catalyzing in vitro both the degradation and synthesis of several synthetic polyesters and polyamides. Here, we present a bioinformatics study that intends to correlate the structural features of cutinases with their catalytic properties to provide rational basis for their effective exploitation, particularly in polymer synthesis and biodegradation. The bioinformatics study used the BioGPS method (Global Positioning System in Biological Space) that computed molecular descriptors based on Molecular Interaction Fields (MIFs) described in the GRID force field. The information was used to generate catalophores, spatial representations of the ability of each enzymatic active site to establish hydrophobic and electrostatic interactions. These tools were exploited for comparing cutinases to other serine-hydrolases enzymes, namely lipases, esterases, amidases and proteases, and for highlighting differences and similarities that might guide rational engineering strategies. Structural features of cutinases with their catalytic properties were correlated. The “catalophore” of cutinases indicate shared features with lipases and esterases. Full article
(This article belongs to the Special Issue Biocatalysis for Green Chemistry)
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15 pages, 1793 KiB  
Article
Optimization and Engineering of a Self-Sufficient CYP102 Enzyme from Bacillus amyloliquefaciens towards Synthesis of In-Chain Hydroxy Fatty Acids
by Li Zong, Yan Zhang, Zhengkang Shao, Yingwu Wang, Zheng Guo, Renjun Gao and Bekir Engin Eser
Catalysts 2021, 11(6), 665; https://0-doi-org.brum.beds.ac.uk/10.3390/catal11060665 - 23 May 2021
Cited by 6 | Viewed by 2809
Abstract
Cytochrome P450 (CYP) mediated enzymatic hydroxylation of fatty acids present a green alternative to chemical synthesis of hydroxy fatty acids (HFAs), which are high-value oleochemicals with various uses in materials industry and medical field. Although many CYPs require the presence of additional reductase [...] Read more.
Cytochrome P450 (CYP) mediated enzymatic hydroxylation of fatty acids present a green alternative to chemical synthesis of hydroxy fatty acids (HFAs), which are high-value oleochemicals with various uses in materials industry and medical field. Although many CYPs require the presence of additional reductase proteins for catalytic activity, self-sufficient CYPs have their reductase partner naturally fused into their catalytic domain, leading to a greatly simplified biotransformation process. A recently discovered self-sufficient CYP, BAMF2522 from Bacillus amyloliquefaciens DSM 7, exhibits novel regioselectivity by hydroxylating in-chain positions of palmitic acid generating ω-1 to ω-7 HFAs, a rare regiodiversity profile among CYPs. Besides, F89I mutant of BAMF2522 expanded hydroxylation up to ω-9 position of palmitic acid. Here, we further characterize this enzyme by determining optimum temperature and pH as well as thermal stability. Moreover, using extensive site-directed and site-saturation mutagenesis, we obtained BAMF2522 variants that demonstrate greatly increased regioselectivity for in-chain positions (ω-4 to ω-9) of various medium to long chain fatty acids. Remarkably, when a six-residue mutant was reacted with palmitic acid, 84% of total product content was the sum of ω-7, ω-8 and ω-9 HFA products, the highest in-chain selectivity observed to date with a self-sufficient CYP. In short, our study demonstrates the potential of a recently identified CYP and its mutants for green and sustainable production of a variety of in-chain hydroxy enriched HFAs. Full article
(This article belongs to the Special Issue Biocatalysis for Green Chemistry)
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12 pages, 3122 KiB  
Article
Integrated Utilization of Dairy Whey in Probiotic β-Galactosidase Production and Enzymatic Synthesis of Galacto-Oligosaccharides
by Feiyu Duan, Renfei Zhao, Jingyi Yang, Min Xiao and Lili Lu
Catalysts 2021, 11(6), 658; https://0-doi-org.brum.beds.ac.uk/10.3390/catal11060658 - 22 May 2021
Cited by 12 | Viewed by 2714
Abstract
This work established an integrated utilization of dairy whey in β-galactosidase production from Lactobacillus bulgaricus and prebiotics synthesis by the probiotic enzyme. A cost-effective whey-based medium was newly developed for culturing Lactobacillus bulgaricus to produce β-galactosidase. The medium was optimized through response surface [...] Read more.
This work established an integrated utilization of dairy whey in β-galactosidase production from Lactobacillus bulgaricus and prebiotics synthesis by the probiotic enzyme. A cost-effective whey-based medium was newly developed for culturing Lactobacillus bulgaricus to produce β-galactosidase. The medium was optimized through response surface methodology (RSM) involving a series of statistical designs, such as the Plackett–Burman design, steepest ascent experiment, and central composite design. Under the optimized medium, the β-galactosidase activity of L. bulgaricus reached 2034 U/L, which was twice that produced from the traditional MRS medium. The cells of L. bulgaricus harvested from the whey-based medium were subsequently treated with lysozyme. The resulting crude enzyme was used as an efficient catalyst, which catalyzed the synthesis of the prebiotic galacto-oligosaccharides (GOS) in a high yield of 44.7% by using whey (200 g/L) as the substrate. The sugar mixture was further purified by activated charcoal adsorption, thereby yielding a high-purity level of 77.6% GOS. Full article
(This article belongs to the Special Issue Biocatalysis for Green Chemistry)
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15 pages, 1589 KiB  
Article
Microbial Removal of Pb(II) Using an Upflow Anaerobic Sludge Blanket (UASB) Reactor
by Jeremiah Chimhundi, Carla Hörstmann, Evans M. N. Chirwa and Hendrik G. Brink
Catalysts 2021, 11(4), 512; https://0-doi-org.brum.beds.ac.uk/10.3390/catal11040512 - 19 Apr 2021
Cited by 8 | Viewed by 2426
Abstract
The main objective of this study was to achieve the continuous biorecovery and bioreduction of Pb(II) using an industrially obtained consortia as a biocatalyst. An upflow anaerobic sludge blanket reactor was used in the treatment process. The bioremediation technique that was applied made [...] Read more.
The main objective of this study was to achieve the continuous biorecovery and bioreduction of Pb(II) using an industrially obtained consortia as a biocatalyst. An upflow anaerobic sludge blanket reactor was used in the treatment process. The bioremediation technique that was applied made use of a yeast extract as the microbial substrate and Pb(NO3)2 as the source of Pb(II). The UASB reactor exhibited removal efficiencies of between 90 and 100% for the inlet Pb concentrations from 80 to 2000 ppm and a maximum removal rate of 1948.4 mg/(L·d) was measured. XRD and XPS analyses of the precipitate revealed the presence of Pb0, PbO, PbS and PbSO4. Supporting experimental work carried out included growth measurements, pH, oxidation–reduction potentials and nitrate levels. Full article
(This article belongs to the Special Issue Biocatalysis for Green Chemistry)
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11 pages, 1304 KiB  
Article
Cascade Biocatalysis Designed for the Allylic Oxidation of α-Pinene
by Giulia R. Gheorghita, Cristina Sora, Sabina Ion, Vasile I. Parvulescu and Madalina Tudorache
Catalysts 2021, 11(1), 134; https://0-doi-org.brum.beds.ac.uk/10.3390/catal11010134 - 18 Jan 2021
Cited by 5 | Viewed by 2395
Abstract
A biocatalytic cascade system using a cocktail of oxidoreductase enzymes (2-1B peroxidase and M120 laccase) was designed for the allylic oxidation of (+)-α-pinene into value-added products (e.g., verbenol and verbenone). The oxidative transformation involved a two-step process as follows: (+)-α-pinene was (i) oxidized [...] Read more.
A biocatalytic cascade system using a cocktail of oxidoreductase enzymes (2-1B peroxidase and M120 laccase) was designed for the allylic oxidation of (+)-α-pinene into value-added products (e.g., verbenol and verbenone). The oxidative transformation involved a two-step process as follows: (+)-α-pinene was (i) oxidized on the allylic position with H2O2 mainly assisted by 2-1B peroxidase leading to verbenol as the principal reaction product, and (ii) directed to verbenone in the presence of M120 laccase responsible for further oxidation of verbenol to verbenone. The reaction environment was ensured by the acetate buffer (0.1 M, pH = 5). Optimum values for the experimental parameters (e.g., concentration of 2-1B peroxidase, M120 laccase, and H2O2) were set up. The biocatalytic cascade process was monitored for 24 h in order to evaluate the process pathway. Maximum performance under optimum conditions was reached after 5 h incubation time (e.g., 80% (+)-α-pinene conversion and 70% yield in verbenol). Therefore, the developed biocatalytic cascade system offered promising perspectives for (+)-α-pinene valorization. Full article
(This article belongs to the Special Issue Biocatalysis for Green Chemistry)
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12 pages, 927 KiB  
Article
Development of a Cofactor Balanced, Multi Enzymatic Cascade Reaction for the Simultaneous Production of L-Alanine and L-Serine from 2-Keto-3-deoxy-gluconate
by Benjamin Begander, Anna Huber, Josef Sperl and Volker Sieber
Catalysts 2021, 11(1), 31; https://0-doi-org.brum.beds.ac.uk/10.3390/catal11010031 - 30 Dec 2020
Cited by 4 | Viewed by 2598
Abstract
Enzymatic reaction cascades represent a powerful tool to convert biogenic resources into valuable chemicals for fuel and commodity markets. Sugars and their breakdown products constitute a significant group of possible substrates for such biocatalytic conversion strategies to value-added products. However, one major drawback [...] Read more.
Enzymatic reaction cascades represent a powerful tool to convert biogenic resources into valuable chemicals for fuel and commodity markets. Sugars and their breakdown products constitute a significant group of possible substrates for such biocatalytic conversion strategies to value-added products. However, one major drawback of sugar cascades is the need for cofactor recycling without using additional enzymes and/or creating unwanted by-products. Here, we describe a novel, multi-enzymatic reaction cascade for the one-pot simultaneous synthesis of L-alanine and L-serine, using the sugar degradation product 2-keto-3-deoxygluconate and ammonium as precursors. To pursue this aim, we used four different, thermostable enzymes, while the necessary cofactor NADH is recycled entirely self-sufficiently. Buffer and pH optimisation in combination with an enzyme titration study yielded an optimised production of 21.3 +/− 1.0 mM L-alanine and 8.9 +/− 0.4 mM L-serine in one pot after 21 h. Full article
(This article belongs to the Special Issue Biocatalysis for Green Chemistry)
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15 pages, 1723 KiB  
Article
Enzyme-Assisted Aqueous Extraction of Cobia Liver Oil and Protein Hydrolysates with Antioxidant Activity
by Yu-Hsiang Wang, Chia-Hung Kuo, Chien-Liang Lee, Wen-Cheng Kuo, Mei-Ling Tsai and Pei-Pei Sun
Catalysts 2020, 10(11), 1323; https://0-doi-org.brum.beds.ac.uk/10.3390/catal10111323 - 14 Nov 2020
Cited by 14 | Viewed by 3402
Abstract
Cobia, Rachycentron canadum, is a medium-size marine fish with emerging global potential for offshore aquaculture. The processing waste, cobia liver, is a raw material rich in polyunsaturated fatty acid oils. In this study, an environmentally friendly green process, aqueous extraction (AE), was [...] Read more.
Cobia, Rachycentron canadum, is a medium-size marine fish with emerging global potential for offshore aquaculture. The processing waste, cobia liver, is a raw material rich in polyunsaturated fatty acid oils. In this study, an environmentally friendly green process, aqueous extraction (AE), was used to extract the cobia liver oil. The effect of cooking time and substrate water ratio on the oil extractability was investigated herein. The cooking time of 15 min, and substrate water ratio of 1:2 obtained the highest extraction efficiency. However, the oil extractability was only 18.8%. Thus, enzyme-assisted aqueous extraction (EAAE) was used to increase oil extractability and recovery of protein hydrolysates. The commercial proteases—including alcalase, papain, trypsin, and pepsin—were employed in pretreated cobia liver in order to increase oil release during AE. The EAAE results showed that maximum oil extractability was 38% by papain pretreatment. EAAE greatly improved the extraction efficiency; the oil extractability was double than that of AE (18.8%). The fatty acid profiles revealed that ω-3 polyunsaturated fatty acid contents of extracted oil obtained from AE and EAAE were 21.3% and 19.5%, respectively. Besides, the cobia liver hydrolysates obtained from EAAE by alcalase, papain, pepsin, and trypsin pretreatment showed scavenge DPPH radical activity with EC50 values of 0.92, 1.03, 0.83, and 0.53 mg, respectively. After in vitro simulated gastrointestinal digestion, the protein hydrolysates exhibited scavenge DPPH radical activity with EC50 values of 1.15, 1.55, 0.98, and 0.76 mg for alcalase, papain, pepsin, and trypsin, respectively. The study showed that the EAAE process can be used for extracting fish oil from fish waste while simultaneously obtaining the protein hydrolysates with antioxidant activity. Full article
(This article belongs to the Special Issue Biocatalysis for Green Chemistry)
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21 pages, 5501 KiB  
Article
Phylogeny and Structure of Fatty Acid Photodecarboxylases and Glucose-Methanol-Choline Oxidoreductases
by Vladimir A. Aleksenko, Deepak Anand, Alina Remeeva, Vera V. Nazarenko, Valentin Gordeliy, Karl-Erich Jaeger, Ulrich Krauss and Ivan Gushchin
Catalysts 2020, 10(9), 1072; https://0-doi-org.brum.beds.ac.uk/10.3390/catal10091072 - 17 Sep 2020
Cited by 16 | Viewed by 5005
Abstract
Glucose-methanol-choline (GMC) oxidoreductases are a large and diverse family of flavin-binding enzymes found in all kingdoms of life. Recently, a new related family of proteins has been discovered in algae named fatty acid photodecarboxylases (FAPs). These enzymes use the energy of light to [...] Read more.
Glucose-methanol-choline (GMC) oxidoreductases are a large and diverse family of flavin-binding enzymes found in all kingdoms of life. Recently, a new related family of proteins has been discovered in algae named fatty acid photodecarboxylases (FAPs). These enzymes use the energy of light to convert fatty acids to the corresponding Cn-1 alkanes or alkenes, and hold great potential for biotechnological application. In this work, we aimed at uncovering the natural diversity of FAPs and their relations with other GMC oxidoreductases. We reviewed the available GMC structures, assembled a large dataset of GMC sequences, and found that one active site amino acid, a histidine, is extremely well conserved among the GMC proteins but not among FAPs, where it is replaced with alanine. Using this criterion, we found several new potential FAP genes, both in genomic and metagenomic databases, and showed that related bacterial, archaeal and fungal genes are unlikely to be FAPs. We also identified several uncharacterized clusters of GMC-like proteins as well as subfamilies of proteins that lack the conserved histidine but are not FAPs. Finally, the analysis of the collected dataset of potential photodecarboxylase sequences revealed the key active site residues that are strictly conserved, whereas other residues in the vicinity of the flavin adenine dinucleotide (FAD) cofactor and in the fatty acid-binding pocket are more variable. The identified variants may have different FAP activity and selectivity and consequently may prove useful for new biotechnological applications, thereby fostering the transition from a fossil carbon-based economy to a bio-economy by enabling the sustainable production of hydrocarbon fuels. Full article
(This article belongs to the Special Issue Biocatalysis for Green Chemistry)
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10 pages, 5098 KiB  
Article
Biosynthesis of Putrescine from L-arginine Using Engineered Escherichia coli Whole Cells
by Hongjie Hui, Yajun Bai, Tai-Ping Fan, Xiaohui Zheng and Yujie Cai
Catalysts 2020, 10(9), 947; https://0-doi-org.brum.beds.ac.uk/10.3390/catal10090947 - 19 Aug 2020
Cited by 11 | Viewed by 3611
Abstract
Putrescine, a biogenic amine, is a highly valued compound in medicine, industry, and agriculture. In this study, we report a whole-cell biocatalytic method in Escherichia coli for the production of putrescine, using L-arginine as the substrate. L-arginine decarboxylase and agmatine ureohydrolase were co-expressed [...] Read more.
Putrescine, a biogenic amine, is a highly valued compound in medicine, industry, and agriculture. In this study, we report a whole-cell biocatalytic method in Escherichia coli for the production of putrescine, using L-arginine as the substrate. L-arginine decarboxylase and agmatine ureohydrolase were co-expressed to produce putrescine from L-arginine. Ten plasmids with different copy numbers and ordering of genes were constructed to balance the expression of the two enzymes, and the best strain was pACYCDuet-speB-speA. The optimal concentration of L-arginine was determined to be 20 mM for this strain. The optimum pH of the biotransformation was 9.5, and the optimum temperature was 45 °C; under these conditions, the yield of putrescine was 98%. This whole-cell biocatalytic method appeared to have great potential for the production of putrescine. Full article
(This article belongs to the Special Issue Biocatalysis for Green Chemistry)
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18 pages, 3424 KiB  
Article
Synthesis of Biogenic Palladium Nanoparticles Using Citrobacter sp. for Application as Anode Electrocatalyst in a Microbial Fuel Cell
by Mpumelelo Thomas Matsena, Shepherd Masimba Tichapondwa and Evans Martin Nkhalambayausi Chirwa
Catalysts 2020, 10(8), 838; https://0-doi-org.brum.beds.ac.uk/10.3390/catal10080838 - 24 Jul 2020
Cited by 18 | Viewed by 3133
Abstract
Palladium (Pd) is a cheap and effective electrocatalyst that is capable of replacing platinum (Pt) in various applications. However, the problem in using chemically synthesized Pd nanoparticles (PdNPs) is that they are mostly fabricated using toxic chemicals under severe conditions. In this study, [...] Read more.
Palladium (Pd) is a cheap and effective electrocatalyst that is capable of replacing platinum (Pt) in various applications. However, the problem in using chemically synthesized Pd nanoparticles (PdNPs) is that they are mostly fabricated using toxic chemicals under severe conditions. In this study, we present a more environmentally-friendly process in fabricating biogenic Pd nanoparticles (Bio-PdNPs) using Citrobacter sp. isolated from wastewater sludge. Successful fabrication of Bio-PdNPs was achieved under anaerobic conditions at pH six and a temperature of 30 °C using sodium formate (HCOONa) as an electron donor. Citrobacter sp. showed biosorption capabilities with no enzymatic contribution to Pd(II) uptake during absence of HCOONa in both live and dead cells. Citrobacter sp. live cells also displayed high enzymatic contribution to the removal of Pd(II) by biological reduction. This was confirmed by Scanning Electron Microscope (SEM), Electron Dispersive Spectroscopy (EDS), and X-ray Diffraction (XRD) characterization, which revealed the presence Bio-PdNPs deposited on the bacterial cells. The bio-PdNPs successfully enhanced the anode performance of the Microbial Fuel Cell (MFC). The MFC with the highest Bio-PdNPs loading (4 mg Bio-PdNP/cm2) achieved a maximum power density of 539.3 mW/m3 (4.01 mW/m2) and peak voltage of 328.4 mV. Full article
(This article belongs to the Special Issue Biocatalysis for Green Chemistry)
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9 pages, 3265 KiB  
Article
Biocatalytic Epoxidation of Cyclooctene to 1,2-Epoxycyclooctane by a Newly Immobilized Aspergillus niger Lipase
by Qingsheng Chen, Fei Peng, Fangzhou Li, Gaohui Xia, Minhua Zong and Wenyong Lou
Catalysts 2020, 10(7), 781; https://0-doi-org.brum.beds.ac.uk/10.3390/catal10070781 - 13 Jul 2020
Cited by 4 | Viewed by 1897
Abstract
A newly immobilized Aspergillus niger lipase (ANL@ZnGlu-MNPs) was employed for the preparation of 1,2-epoxycyclooctane by oxidation of cyclooctene. The chosen variables, including substrate concentration, reaction temperature, immobilized enzyme dose, and H2O2 dose, were optimized in the reaction system of ethyl [...] Read more.
A newly immobilized Aspergillus niger lipase (ANL@ZnGlu-MNPs) was employed for the preparation of 1,2-epoxycyclooctane by oxidation of cyclooctene. The chosen variables, including substrate concentration, reaction temperature, immobilized enzyme dose, and H2O2 dose, were optimized in the reaction system of ethyl acetate. The yield and the enantiomeric excess of the product were achieved at 56.8% and 84.1%, respectively, under the following optimum reaction conditions: the concentration of substrate (cyclooctene) was 150 mM, the dosages of immobilized enzyme (ANL@ZnGlu-MNPs) and hydrogen peroxide were respectively 100 mg and 4.4 mmol, and the reaction was carried out in the system of 4 mL ethyl acetate at 40 °C. Further study on the operational stability of ANL@ZnGlu-MNPs showed that more than 51.6% of product yield was obtained after reusing for ten batches. A novel immobilized lipase was prepared and applied to synthesize 1,2-epoxycyclooctane from cyclooctene. Although ANL@ZnGlu-MNPs performs well in operational stability and the reaction can achieve high enantiomeric purity of the product, the yield of the catalytic reaction needs to be further improved. Full article
(This article belongs to the Special Issue Biocatalysis for Green Chemistry)
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Review

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30 pages, 9890 KiB  
Review
Biocatalytic Oxidation of Alcohols
by Hendrik Puetz, Eva Puchľová, Kvetoslava Vranková and Frank Hollmann
Catalysts 2020, 10(9), 952; https://0-doi-org.brum.beds.ac.uk/10.3390/catal10090952 - 20 Aug 2020
Cited by 31 | Viewed by 9921
Abstract
Enzymatic methods for the oxidation of alcohols are critically reviewed. Dehydrogenases and oxidases are the most prominent biocatalysts, enabling the selective oxidation of primary alcohols into aldehydes or acids. In the case of secondary alcohols, region and/or enantioselective oxidation is possible. In this [...] Read more.
Enzymatic methods for the oxidation of alcohols are critically reviewed. Dehydrogenases and oxidases are the most prominent biocatalysts, enabling the selective oxidation of primary alcohols into aldehydes or acids. In the case of secondary alcohols, region and/or enantioselective oxidation is possible. In this contribution, we outline the current state-of-the-art and discuss current limitations and promising solutions. Full article
(This article belongs to the Special Issue Biocatalysis for Green Chemistry)
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Other

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13 pages, 9358 KiB  
Perspective
Lignocellulosic Waste Pretreatment Solely via Biocatalysis as a Partial Simultaneous Lignino-Holocellulolysis Process
by Justine Oma Angadam, Seteno Karabo Obed Ntwampe, Boredi Silas Chidi, Jun Wei Lim and Vincent Ifeanyi Okudoh
Catalysts 2021, 11(6), 668; https://0-doi-org.brum.beds.ac.uk/10.3390/catal11060668 - 24 May 2021
Cited by 4 | Viewed by 2335
Abstract
Human endeavors generate a significant quantity of bio-waste, even lignocellulosic waste, due to rapid industrialization and urbanization, and can cause pollution to aquatic ecosystems, and contribute to detrimental animal and human health because of the toxicity of consequent hydrolysis products. This paper contributes [...] Read more.
Human endeavors generate a significant quantity of bio-waste, even lignocellulosic waste, due to rapid industrialization and urbanization, and can cause pollution to aquatic ecosystems, and contribute to detrimental animal and human health because of the toxicity of consequent hydrolysis products. This paper contributes to a new understanding of the lignocellulosic waste bio-pretreatment process from a literature review, which can provide better biorefinery operational outcomes. The simultaneous partial biological lignin, cellulose and hemicellulose lysis, i.e., simultaneous semi-lignino-holocellulolysis, is aimed at suggesting that when ligninolysis ensues, holocellulolysis is simultaneously performed for milled lignocellulosic waste instead of having a sequential process of initial ligninolysis and subsequent holocellulolysis as is currently the norm. It is presumed that such a process can be solely performed by digestive enzyme cocktails from the monkey cups of species such as Nepenthes, white and brown rot fungi, and some plant exudates. From the literature review, it was evident that the pretreatment of milled lignocellulosic waste is largely incomplete, and ligninolysis including holocellulolysis ensues simultaneously when the waste is milled. It is further proposed that lignocellulosic waste pretreatment can be facilitated using an environmentally friendly approach solely using biological means. For such a process to be understood and applied on an industrial scale, an interdisciplinary approach using process engineering and microbiology techniques is required. Full article
(This article belongs to the Special Issue Biocatalysis for Green Chemistry)
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