Biocatalysis and Fermentation—Enzyme Production and Whole Cell Biocatalysis

A special issue of Fermentation (ISSN 2311-5637). This special issue belongs to the section "Microbial Metabolism, Physiology & Genetics".

Deadline for manuscript submissions: closed (30 November 2019) | Viewed by 33430

Special Issue Editor


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Guest Editor
School of Pharmacy and Biomolecular Sciences, University of Brighton, Brighton, UK
Interests: enzyme engineering; yeast as models for human diseases; yeast growth under adverse conditions

Special Issue Information

Dear Colleagues,

Biocatalysis offers significant opportunities. Enzymes catalyse a vast range of chemical reactions, often with exquisite regio- and stereo-selectivity. They often do so at faster rates than traditional chemical catalysts and at lower temperatures and pressures. Enzymes typically operate in aqueous solution and are naturally biodegradable. Their potential for exploitation in “green chemistry” is substantial. The production of enzymes for biocatalysis typically requires the expression of the protein in a recombinant host, often bacteria or yeasts. Optimisation of fermentation conditions can result in significant advantages through the improvement of yield, quality and purity of the enzyme. Site-directed mutagenesis methods can be applied to engineer enzymes for altered specificity or improved stability. Alternatively, whole cells can be used as reaction vessels to synthesise particular chemicals. Often this requires engineering of the metabolic pathways present in the cells to redirect biosynthesis towards the desired product. Again, optimisation of the growth conditions is likely to be necessary to maximise yield. This Special Issue focuses on the use of microbial cells for the production of biocatalysts and in whole cell biocatalysis. Papers describing the optimisation of the production of enzymes and the operation of whole cell biocatalysis are encouraged as are papers describing theoretical approaches which can be applied to yield improvement.

Prof. David J. Timson
Guest Editor

Manuscript Submission Information

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Keywords

  • biocatalysis
  • recombinant enzyme
  • whole cell biocatalysis
  • protein overexpression
  • enzyme engineering
  • metabolic pathway engineering
  • green chemistry
  • bioreactors
  • enzyme biotechnology
  • yield improvement

Published Papers (6 papers)

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Research

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13 pages, 4565 KiB  
Article
Reusability of Immobilized Cells for Subsequent Balsamic-Styled Vinegar Fermentations
by Ucrecia F. Hutchinson, Seteno K. O. Ntwampe, Boredi S. Chidi, Maxwell Mewa-Ngongang, Heinrich W. du Plessis, Mardé Booyse and Neil P. Jolly
Fermentation 2020, 6(4), 103; https://doi.org/10.3390/fermentation6040103 - 29 Oct 2020
Cited by 5 | Viewed by 2783
Abstract
Cell immobilization is a process augmentation technique aimed at improving microbial survival and activity under stressful conditions. It offers the opportunity to reuse the immobilized cells for several fermentation cycles. The present study investigated the use of recycled cells entrapped in calcium-alginate beads [...] Read more.
Cell immobilization is a process augmentation technique aimed at improving microbial survival and activity under stressful conditions. It offers the opportunity to reuse the immobilized cells for several fermentation cycles. The present study investigated the use of recycled cells entrapped in calcium-alginate beads and cells adsorbed on corncobs (CC) and oakwood chips (OWC) in subsequent fermentation cycles for balsamic-styled vinegar (BSV) production. Sugars, pH, alcohol and total acidity were monitored during fermentation. Microbial activity and product formation declined when immobilized cells were reused for the second cycle for CC and OWC fermentations. Recycled cells entrapped in Ca-alginate beads completed the second cycle of fermentations, albeit at reduced acetification rates compared to the first cycle. Scanning electron microscope (SEM) imaging results further showed a substantial the structural integrity loss for Ca-alginate beads after the first cycle, and with minor changes in the structural integrity of CC. The OWC displayed a similar morphological structure before and after the first cycle. The sensory results showed that BSV produced using immobilized cells with Ca-alginate beads and CC was palatable, while those produced using OWC had negative attributes. Ca-alginate beads offered better protection for the fermentation consortium for culture reusability in BSV fermentations. Full article
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10 pages, 769 KiB  
Article
Non-Conventional Yeasts as Sources of Ene-Reductases for the Bioreduction of Chalcones
by Sara Filippucci, Giorgia Tasselli, Fatima-Zohra Kenza Labbani, Benedetta Turchetti, Maria Rita Cramarossa, Pietro Buzzini and Luca Forti
Fermentation 2020, 6(1), 29; https://doi.org/10.3390/fermentation6010029 - 21 Feb 2020
Cited by 9 | Viewed by 3591
Abstract
Thirteen Non-Conventional Yeasts (NCYs) have been investigated for their ability to reduce activated C=C bonds of chalcones to obtain the corresponding dihydrochalcones. A possible correlation between bioreducing capacity of the NCYs and the substrate structure was estimated. Generally, whole-cells of the NCYs were [...] Read more.
Thirteen Non-Conventional Yeasts (NCYs) have been investigated for their ability to reduce activated C=C bonds of chalcones to obtain the corresponding dihydrochalcones. A possible correlation between bioreducing capacity of the NCYs and the substrate structure was estimated. Generally, whole-cells of the NCYs were able to hydrogenate the C=C double bond occurring in (E)-1,3-diphenylprop-2-en-1-one, while worthy bioconversion yields were obtained when the substrate exhibited the presence of a deactivating electron-withdrawing Cl substituent on the B-ring. On the contrary, no conversion was generally found, with a few exceptions, in the presence of an activating electron-donating substituent OH. The bioreduction aptitude of the NCYs was apparently correlated to the logP value: Compounds characterized by a higher logP exhibited a superior aptitude to be reduced by the NCYs than compounds with a lower logP value. Full article
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17 pages, 2151 KiB  
Article
Optimization of β-galactosidase Production by Batch Cultures of Lactobacillus leichmannii 313 (ATCC 7830™)
by Yongjin Deng, Min Xu, Dawei Ji and Dominic Agyei
Fermentation 2020, 6(1), 27; https://doi.org/10.3390/fermentation6010027 - 15 Feb 2020
Cited by 16 | Viewed by 10637
Abstract
The endoenzyme β-galactosidase (β-d-galactoside galactohydrolase; EC 3.2.1.23) has been used at industrial scales for the preparation of lactose-free milk and for the conversion of lactose to galacto-oligosaccharides (GOS) prebiotics. In this study, using Plackett–Burman (PB) design and the response surface methodology [...] Read more.
The endoenzyme β-galactosidase (β-d-galactoside galactohydrolase; EC 3.2.1.23) has been used at industrial scales for the preparation of lactose-free milk and for the conversion of lactose to galacto-oligosaccharides (GOS) prebiotics. In this study, using Plackett–Burman (PB) design and the response surface methodology (RSM), the batch growth conditions for the production of β-galactosidase in DeMan-Rogosa-Sharpe (MRS) media have been studied and optimized for Lactobacillus leichmannii 313 (ATCC 7830™) for the first time. The incubation temperature (30  <  T  <  55 °C), starting pH (5.5  <  pH  <  7.5), and carbon source (glucose, lactose, galactose, fructose, and sucrose) were selected as the significant variables for optimization. The maximum crude β-galactosidase production (measured by specific activity) was 4.5 U/mg proteins and was obtained after 12 h of fermentation. The results of the PB design and further optimization by RSM showed that the initial pH of 7.0 and 15.29 g/L of lactose were the levels that gave the optimum observed and predicted β-galactosidase activities of 23.13 U/mg and 23.40 U/mg, respectively. Through RSM optimization, β-galactosidase production increased significantly (over five-fold) in optimized medium (23.13 U/mg), compared with unoptimized medium (4.5 U/mg). Moreover, the crude enzyme obtained was able to hydrolyze lactose and also produce galacto-oligosaccharides. Because its ability to produce β-galactosidase was significantly improved through optimization by RSM, L. leichmannii 313 can serve as a potential source of β-galactosidase for food applications at an industrial scale. Full article
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8 pages, 1852 KiB  
Article
Basidiomycotic Yeast Cryptococcus diffluens Converts l-Galactonic Acid to the Compound on the Similar Metabolic Pathway in Ascomycetes
by Takeo Matsubara, Michihiko Kataoka and Masao Kishida
Fermentation 2019, 5(3), 73; https://doi.org/10.3390/fermentation5030073 - 5 Aug 2019
Viewed by 3171
Abstract
(1) Background: It has been shown that d-galacturonic acid is converted to l-galactonic acid by the basidiomycotic yeast, Cryptococcus diffluens. However, two pathways are hypothesized for the l-galactonic acid conversion process in C. diffluens. One is similar to [...] Read more.
(1) Background: It has been shown that d-galacturonic acid is converted to l-galactonic acid by the basidiomycotic yeast, Cryptococcus diffluens. However, two pathways are hypothesized for the l-galactonic acid conversion process in C. diffluens. One is similar to the conversion process of the filamentous fungi in d-galacturonic acid metabolism and another is the conversion process to l-ascorbic acid, reported in the related yeast, C. laurentii. It is necessary to determine which, if either, process occurs in C. diffluens in order to produce novel value-added products from d-galacturonic acid using yeast strains. (2) Methods: The diethylaminoethy (DEAE)-fractionated enzyme was prepared from the cell-free extract of C. diffluens by the DEAE column chromatography. The l-galactonic acid conversion activity was assayed using DEAE-fractionated enzyme and the converted product was detected and fractionated by high-performance anion-exchange chromatography. Then, the molecular structure was identified by nuclear magnetic resonance analysis. (3) Results: The product showed similar chemical properties to 2-keto-3-deoxy-l-galactonic acid (l-threo-3-deoxy-hexulosonic acid). (4) Conclusions: It is suggested that l-galactonic acid is converted to 2-keto-3-deoxy-l-galactonic acid by dehydratase in C. diffluens. The l-galactonic acid conversion process of C. diffluens is a prioritized pathway, similar to the pathway of ascomycetes. Full article
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Review

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19 pages, 582 KiB  
Review
Yeast Cellular Stress: Impacts on Bioethanol Production
by Joshua Eardley and David J. Timson
Fermentation 2020, 6(4), 109; https://doi.org/10.3390/fermentation6040109 - 13 Nov 2020
Cited by 24 | Viewed by 6344
Abstract
Bioethanol is the largest biotechnology product and the most dominant biofuel globally. Saccharomyces cerevisiae is the most favored microorganism employed for its industrial production. However, obtaining maximum yields from an ethanol fermentation remains a technical challenge, since cellular stresses detrimentally impact on the [...] Read more.
Bioethanol is the largest biotechnology product and the most dominant biofuel globally. Saccharomyces cerevisiae is the most favored microorganism employed for its industrial production. However, obtaining maximum yields from an ethanol fermentation remains a technical challenge, since cellular stresses detrimentally impact on the efficiency of yeast cell growth and metabolism. Ethanol fermentation stresses potentially include osmotic, chaotropic, oxidative, and heat stress, as well as shifts in pH. Well-developed stress responses and tolerance mechanisms make S. cerevisiae industrious, with bioprocessing techniques also being deployed at industrial scale for the optimization of fermentation parameters and the effective management of inhibition issues. Overlap exists between yeast responses to different forms of stress. This review outlines yeast fermentation stresses and known mechanisms conferring stress tolerance, with their further elucidation and improvement possessing the potential to improve fermentation efficiency. Full article
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9 pages, 204 KiB  
Review
Four Challenges for Better Biocatalysts
by David J. Timson
Fermentation 2019, 5(2), 39; https://doi.org/10.3390/fermentation5020039 - 9 May 2019
Cited by 17 | Viewed by 4558
Abstract
Biocatalysis (the use of biological molecules or materials to catalyse chemical reactions) has considerable potential. The use of biological molecules as catalysts enables new and more specific syntheses. It also meets many of the core principles of “green chemistry”. While there have been [...] Read more.
Biocatalysis (the use of biological molecules or materials to catalyse chemical reactions) has considerable potential. The use of biological molecules as catalysts enables new and more specific syntheses. It also meets many of the core principles of “green chemistry”. While there have been some considerable successes in biocatalysis, the full potential has yet to be realised. This results, partly, from some key challenges in understanding the fundamental biochemistry of enzymes. This review summarises four of these challenges: the need to understand protein folding, the need for a qualitative understanding of the hydrophobic effect, the need to understand and quantify the effects of organic solvents on biomolecules and the need for a deep understanding of enzymatic catalysis. If these challenges were addressed, then the number of successful biocatalysis projects is likely to increase. It would enable accurate prediction of protein structures, and the effects of changes in sequence or solution conditions on these structures. We would be better able to predict how substrates bind and are transformed into products, again leading to better enzyme engineering. Most significantly, it may enable the de novo design of enzymes to catalyse specific reactions. Full article
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