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Catalysts
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Biocatalysis and Biotransformations
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Biocatalysis and Biotransformations

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

Deadline for manuscript submissions: closed (30 November 2017) | Viewed by 141643

Special Issue Editor

Dr. Manuel Ferrer

E-Mail
Guest Editor
CSIC, Institute of Catalysis, 28049 Madrid, Spain
Interests: enzyme functions; metagenomics; protein engineering; bio-catalytic molecule modification; enzyme immobilization

Special Issue Information

Dear Colleagues,

The end of the twentieth century has experienced a revolution in the life sciences and, specifically, in biocatalysis. In this sense, the relation between chemistry, biology and microbiology is currently under a deep transformation influenced by new technologies that included synthetic biology and micro-cultivation for whole-cell design and isolation, next generation sequencing and so-called OMIC technologies (genomics, transcriptomics, proteomics, and metabolomics) for the discovery of biocatalysts and their functions, modern protein engineering technologies and protein design algorithms, and combinatorial and rational methods to generate new materials with which stabilized biocatalysts. Through a series of reactions, biocatalysts can be used for the economic and sustainable production of highly valuable customized and functionalized chemicals or materials. At this end, the final catalytic properties of a biocatalyst will be mainly the result of substrate arrangement in its active site driven by its polypeptide sequence and structure, and the influence that the engineering, immobilization or design process additionally exerts. In case of whole cells biocatalysts control of enzyme content, cell characteristics, and presence of accessory genes are important contributors to their final utilization in biotransformations.

The aim of this Special Issue on “Biocatalysis and Biotransformations” is to cover promising recent research and novel trends in biocatalysts specifically designed and/or isolated to solve on-going problems in catalysis. Contributions from all areas of homogeneous and supported catalysis, based on experimental results, OMIC tools and cultivation approaches, combinatorial and rational methods, molecular modeling, and synthetic biology, would be of great interest. Advances in these areas should be focused in solving relevant catalytic problems. Topics including (i) the discovery, design and utilization of promiscuous biocatalysts for performing efficiently multiple biotransformations; (ii) selective C-C, C-O and C-N functionalization; (iii) synthesis of novel bioactive molecules; (iv) novel efficient electro-biocatalysts; (v) microfluidic single-cell biocatalysis; (vi) isolation, design and construction of new whole cell biocatalysts; (vii)  design of novel immobilized biocatalysts; and (viii) novel catalytic reactions of interest in industrial settings will be covered. Original results providing new insights into biocatalysts specifically designed to solve actual problems in catalysis are particularly welcome. Contributions from all areas of homogeneous and supported catalysis, based on experimental results and/or molecular modeling, would be of great interest.

Dr. Manuel Ferrer
Guest Editor

Manuscript Submission Information

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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

  • Bioactives

  • Biocatalysts

  • Biotrasnformations

  • Bond activation and functionalization

  • C–C, C–O, and C–N bond activation/functionalization

  • Electrobiocatalysts

  • Fine chemicals

  • Functionalized materials

  • Homogenous catalysis

  • Mechanistic insight

  • Metagenomics

  • Microfluidic

  • Promiscuity

  • Protein engineering

  • Structure-reactivity

  • Supported catalysis

  • Sustainability

  • Theoretical study

Published Papers (26 papers)

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Editorial

Jump to: Research

6 pages, 199 KiB  
Editorial
Biocatalysis and Biotransformations
by Manuel Ferrer
Catalysts 2018, 8(5), 216; https://doi.org/10.3390/catal8050216 - 17 May 2018
Cited by 3 | Viewed by 3146
Abstract
n/a Full article
(This article belongs to the Special Issue Biocatalysis and Biotransformations)

Research

Jump to: Editorial

9 pages, 1701 KiB  
Communication
Functional Analysis of Methylomonas sp. DH-1 Genome as a Promising Biocatalyst for Bioconversion of Methane to Valuable Chemicals
by Anh Duc Nguyen, In Yeub Hwang, Ok Kyung Lee, Dong Hoon Hur, Young Chan Jeon, Susila Hadiyati, Min-Sik Kim, Sung Ho Yoon, Haeyoung Jeong and Eun Yeol Lee
Catalysts 2018, 8(3), 117; https://doi.org/10.3390/catal8030117 - 16 Mar 2018
Cited by 18 | Viewed by 6528
Abstract
Methylomonas sp. DH-1, newly isolated from the activated sludge of a brewery plant, has been used as a promising biocatalytic platform for the conversion of methane to value-added chemicals. Methylomonas sp. DH-1 can efficiently convert methane and propane into methanol and acetone with [...] Read more.
Methylomonas sp. DH-1, newly isolated from the activated sludge of a brewery plant, has been used as a promising biocatalytic platform for the conversion of methane to value-added chemicals. Methylomonas sp. DH-1 can efficiently convert methane and propane into methanol and acetone with a specific productivity of 4.31 and 0.14 mmol/g cell/h, the highest values ever reported, respectively. Here, we present the complete genome sequence of Methylomonas sp. DH-1 which consists of a 4.86 Mb chromosome and a 278 kb plasmid. The existence of a set of genes related to one-carbon metabolism and various secondary metabolite biosynthetic pathways including carotenoid pathways were identified. Interestingly, Methylomonas sp. DH-1 possesses not only the genes of the ribulose monophosphate cycle for type I methanotrophs but also the genes of the serine cycle for type II. Methylomonas sp. DH-1 accumulated 80 mM succinate from methane under aerobic conditions, because DH-1 has 2-oxoglutarate dehydrogenase activity and the ability to operate the full TCA cycle. Availability of the complete genome sequence of Methylomonas sp. DH-1 enables further investigations on the metabolic engineering of this strain for the production of value-added chemicals from methane. Full article
(This article belongs to the Special Issue Biocatalysis and Biotransformations)
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8 pages, 1882 KiB  
Communication
Relationships between Substrate Promiscuity and Chiral Selectivity of Esterases from Phylogenetically and Environmentally Diverse Microorganisms
by Cristina Coscolín, Mónica Martínez-Martínez, Jennifer Chow, Rafael Bargiela, Antonio García-Moyano, Gro E. K. Bjerga, Alexander Bollinger, Runar Stokke, Ida H. Steen, Olga V. Golyshina, Michail M. Yakimov, Karl-Erich Jaeger, Alexander F. Yakunin, Wolfgang R. Streit, Peter N. Golyshin and Manuel Ferrer
Catalysts 2018, 8(1), 10; https://doi.org/10.3390/catal8010010 - 05 Jan 2018
Cited by 8 | Viewed by 4631
Abstract
Substrate specificity and selectivity of a biocatalyst are determined by the protein sequence and structure of its active site. Finding versatile biocatalysts acting against multiple substrates while at the same time being chiral selective is of interest for the pharmaceutical and chemical industry. [...] Read more.
Substrate specificity and selectivity of a biocatalyst are determined by the protein sequence and structure of its active site. Finding versatile biocatalysts acting against multiple substrates while at the same time being chiral selective is of interest for the pharmaceutical and chemical industry. However, the relationships between these two properties in natural microbial enzymes remain underexplored. Here, we performed an experimental analysis of substrate promiscuity and chiral selectivity in a set of 145 purified esterases from phylogenetically and environmentally diverse microorganisms, which were assayed against 96 diverse esters, 20 of which were enantiomers. Our results revealed a negative correlation between substrate promiscuity and chiral selectivity in the evaluated enzymes. Esterases displaying prominent substrate promiscuity and large catalytic environments are characterized by low chiral selectivity, a feature that has limited commercial value. Although a low level of substrate promiscuity does not guarantee high chiral selectivity, the probability that esterases with smaller active sites possess chiral selectivity factors of interest for industry (>25) is significantly higher than for promiscuous enzymes. Together, the present study unambiguously demonstrates that promiscuous and selective esterases appear to be rare in nature and that substrate promiscuity can be used as an indicator of the chiral selectivity level of esterases, and vice versa. Full article
(This article belongs to the Special Issue Biocatalysis and Biotransformations)
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19 pages, 3707 KiB  
Article
2′-Deoxyribosyltransferase from Bacillus psychrosaccharolyticus: A Mesophilic-Like Biocatalyst for the Synthesis of Modified Nucleosides from a Psychrotolerant Bacterium
by Alba Fresco-Taboada, Jesús Fernández-Lucas, Carmen Acebal, Miguel Arroyo, Fernando Ramón, Isabel De la Mata and José Miguel Mancheño
Catalysts 2018, 8(1), 8; https://doi.org/10.3390/catal8010008 - 03 Jan 2018
Cited by 16 | Viewed by 4636
Abstract
Structure-function relationships of a novel 2′-deoxyribosyltransferase from the psychrotolerant bacterium Bacillus psychrosaccharolyticus (BpNDT) have been exhaustively studied by biochemical and high resolution crystallographic analyses. Despite BpNDT exhibiting some structural features characteristic of cold-adapted enzymes such as localized flexibility in critical [...] Read more.
Structure-function relationships of a novel 2′-deoxyribosyltransferase from the psychrotolerant bacterium Bacillus psychrosaccharolyticus (BpNDT) have been exhaustively studied by biochemical and high resolution crystallographic analyses. Despite BpNDT exhibiting some structural features characteristic of cold-adapted enzymes such as localized flexibility in critical loops, its biochemical properties are typical of mesophilic enzymes. BpNDT is a highly symmetrical homohexamer with tightly associated subunits that possesses flexible and short loops bordering the active sites. The catalytic center is essentially identical to that of other mesophilic homologues. Moreover, BpNDT shows that it is a mesophilic-like enzyme since it is not heat-labile and exhibits an apparent unfolding temperature (Tm) of 49 °C, being active during 96 h at 40 and 50 °C. Finally, BpNDT synthesizes natural and modified nucleosides, with preference for purines as acceptors and pyrimidine nucleosides as donors. Remarkably, the synthesis of several therapeutic nucleosides has been efficiently carried out. In this sense, 5-hydroxymethyl-2′-deoxyuridine (5-HMdUrd), 7-deaza-6-hydroxypurine-2′-deoxyriboside (7-DHPdRib) and theophylline-2′-deoxyriboside were synthesized for the first time by an NDT enzyme, showing the biotechnological interest of BpNDT. Full article
(This article belongs to the Special Issue Biocatalysis and Biotransformations)
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12 pages, 1047 KiB  
Article
One-Pot Multi-Enzymatic Production of Purine Derivatives with Application in Pharmaceutical and Food Industry
by Javier Acosta, Jon Del Arco, Sara Martinez-Pascual, Vicente Javier Clemente-Suárez and Jesús Fernández-Lucas
Catalysts 2018, 8(1), 9; https://doi.org/10.3390/catal8010009 - 01 Jan 2018
Cited by 19 | Viewed by 5334
Abstract
Biocatalysis reproduce nature’s synthetic strategies in order to synthesize different organic compounds. Natural metabolic pathways usually involve complex networks to support cellular growth and survival. In this regard, multi-enzymatic systems are valuable tools for the production of a wide variety of organic compounds. [...] Read more.
Biocatalysis reproduce nature’s synthetic strategies in order to synthesize different organic compounds. Natural metabolic pathways usually involve complex networks to support cellular growth and survival. In this regard, multi-enzymatic systems are valuable tools for the production of a wide variety of organic compounds. Methods: The production of different purine nucleosides and nucleoside-5′-monophosphates has been performed for first time, catalyzed by the sequential action of 2′-deoxyribosyltransferase from Lactobacillus delbrueckii (LdNDT) and hypoxanthine-guanine-xanthine phosphoribosyltransferase from Thermus themophilus HB8 (TtHGXPRT). Results: The biochemical characterization of LdNDT reveals that the enzyme is active and stable in a broad range of pH, temperature, and ionic strength. Substrate specificity studies showed a high promiscuity in the recognition of purine analogues. Finally, the enzymatic production of different purine derivatives was performed to evaluate the efficiency of multi-enzymatic system LdNDT/TtHGXPRT. Conclusions: The production of different therapeutic purine nucleosides was efficiently catalyzed by LdNDT/TtHGXPRT. In addition, the resulting by-products were converted to IMP and GMP. Taking all of these features, this bioprocess entails an efficient, sustainable, and economical alternative to chemical synthetic methods. Full article
(This article belongs to the Special Issue Biocatalysis and Biotransformations)
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1514 KiB  
Article
Biosynthesis of Medium- to Long-Chain α,ω-Diols from Free Fatty Acids Using CYP153A Monooxygenase, Carboxylic Acid Reductase, and E. coli Endogenous Aldehyde Reductases
by Md Murshidul Ahsan, Sihyong Sung, Hyunwoo Jeon, Mahesh D. Patil, Taeowan Chung and Hyungdon Yun
Catalysts 2018, 8(1), 4; https://doi.org/10.3390/catal8010004 - 24 Dec 2017
Cited by 33 | Viewed by 5547
Abstract
α,ω-Diols are important monomers widely used for the production of polyesters and polyurethanes. Here, biosynthesis of α,ω-diols (C8–C16) from renewable free fatty acids using CYP153A monooxygenase, carboxylic acid reductase, and E. coli endogenous aldehyde reductases is reported. The highest [...] Read more.
α,ω-Diols are important monomers widely used for the production of polyesters and polyurethanes. Here, biosynthesis of α,ω-diols (C8–C16) from renewable free fatty acids using CYP153A monooxygenase, carboxylic acid reductase, and E. coli endogenous aldehyde reductases is reported. The highest yield of α,ω-diol was achieved for the production of 1,12-dodecanediol. In the nicotinamide adenine dinucleotide phosphate (NADPH) cofactor regeneration system, 5 g/L of 1,12-dodecanediol was synthesized in 24 h reaction from the commercial ω-hydroxy dodecanoic acid. Finally, 1.4 g/L 1,12-dodecanediol was produced in a consecutive approach from dodecanoic acids. The results of this study demonstrated the scope of the potential development of bioprocesses to substitute the petroleum-based products in the polymer industry. Full article
(This article belongs to the Special Issue Biocatalysis and Biotransformations)
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2633 KiB  
Article
Green Synthesis of Ultraviolet Absorber 2-Ethylhexyl Salicylate: Experimental Design and Artificial Neural Network Modeling
by Shang-Ming Huang, Tzu-Hsiang Hung, Yung-Chuan Liu, Chia-Hung Kuo and Chwen-Jen Shieh
Catalysts 2017, 7(11), 342; https://doi.org/10.3390/catal7110342 - 13 Nov 2017
Cited by 7 | Viewed by 6006
Abstract
2-Ethylhexyl salicylate, an ultraviolet filter, is widely used to protect skin against sunlight-induced harmful effects in the cosmetic industry. In this study, the green synthesis of 2-ethylhexyl salicylate using immobilized lipase through a solvent-free and reduced pressure evaporation system was investigated. A Box–Behnken [...] Read more.
2-Ethylhexyl salicylate, an ultraviolet filter, is widely used to protect skin against sunlight-induced harmful effects in the cosmetic industry. In this study, the green synthesis of 2-ethylhexyl salicylate using immobilized lipase through a solvent-free and reduced pressure evaporation system was investigated. A Box–Behnken design was employed to develop an artificial neural network (ANN) model. The parameters for an optimal architecture of an ANN were set out: a quick propagation algorithm, a hyperbolic tangent transfer function, 10,000 iterations, and six nodes within the hidden layer. The best-fitting performance of the ANN was determined by the coefficient of determination and the root-mean-square error between the correlation of predicted and experimental data, indicating that the ANN displayed excellent data-fitting properties. Finally, the experimental conditions of synthesis were well established with the optimal parameters to obtain a high conversion of 2-ethylhexyl salicylate. In conclusion, this study efficiently replaces the traditional solvents with a green process for the synthesis of 2-ethylhexyl salicylate to avoid environmental contamination, and this process is well-modeled by a methodological ANN for optimization, which might be a benefit for industrial production. Full article
(This article belongs to the Special Issue Biocatalysis and Biotransformations)
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2696 KiB  
Article
Production of 4-Ene-3-ketosteroids in Corynebacterium glutamicum
by Julia García-Fernández, Beatriz Galán, Carmen Felpeto-Santero, José L. Barredo and José L. García
Catalysts 2017, 7(11), 316; https://doi.org/10.3390/catal7110316 - 27 Oct 2017
Cited by 6 | Viewed by 4021
Abstract
Corynebacterium glutamicum has been widely used for the industrial production of amino acids and many value-added chemicals; however, it has not been exploited for the production of steroids. Using C. glutamicum as a cellular biocatalyst we have expressed the 3β-hydroxysteroid dehydrogenase/isomerase MSMEG_5228 from [...] Read more.
Corynebacterium glutamicum has been widely used for the industrial production of amino acids and many value-added chemicals; however, it has not been exploited for the production of steroids. Using C. glutamicum as a cellular biocatalyst we have expressed the 3β-hydroxysteroid dehydrogenase/isomerase MSMEG_5228 from Mycobacterium smegmatis to demonstrate that the resulting recombinant strain is able to oxidize in vivo C19 and C21 3-OH-steroids to their corresponding keto-derivatives. This new approach constitutes a proof of concept of a biotechnological process for producing value-added intermediates such as 4-pregnen-16α,17α-epoxy-16β-methyl-3,20-dione. Full article
(This article belongs to the Special Issue Biocatalysis and Biotransformations)
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2200 KiB  
Article
Improved Catalytic Performance of Lipase Supported on Clay/Chitosan Composite Beads
by Ni Tu, Jianxin Shou, Huaping Dong, Jin Huang and Yimin Li
Catalysts 2017, 7(10), 302; https://doi.org/10.3390/catal7100302 - 13 Oct 2017
Cited by 13 | Viewed by 3999
Abstract
Clay/chitosan composite beads were prepared and used as the carrier to support lipase by adsorption, to improve the activity and stability of lipase in the hydrolysis of olive oil. Under conditions of pH 6.0, 25 °C and adsorption for 10 h, immobilized lipases [...] Read more.
Clay/chitosan composite beads were prepared and used as the carrier to support lipase by adsorption, to improve the activity and stability of lipase in the hydrolysis of olive oil. Under conditions of pH 6.0, 25 °C and adsorption for 10 h, immobilized lipases on chitosan bead (CB–lipase) and three clay/chitosan composite beads, at different clay to chitosan proportions of 1:8 (CCB-8-lipase), 1:5 (CCB-5-lipase) and 1:3 (CCB-3-lipase), were prepared. By comparing the activity of these immobilized lipases, CCB-5-lipase showed the highest activity, followed by CCB-8-lipase > CCB-3-lipase > CB-lipase; this improvement was attributed to the synergetic effect of enrichment of olive oil by clay at the reaction surface and better biocompatibility of chitosan with lipase molecules. The optimum pH and temperature in the reaction respectively changed from 7.0 and 30 °C for free lipase to 7.5 and 35 °C for immobilized forms. Furthermore, the thermal stability and repeated usability of these immobilized lipases were sequenced as CCB-3-lipase > CCB-5-lipase > CCB-8-lipase > CB–lipase, due to greater rigidity of immobilized lipase with the addition of clay, which was further confirmed by SEM. The study shows that the incorporation of clay with chitosan creates a good synergetic effect to improve the catalytic performance of immobilized lipase on clay/chitosan composite. Full article
(This article belongs to the Special Issue Biocatalysis and Biotransformations)
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2404 KiB  
Article
Immobilization of Pyrroloquinoline Quinone-Dependent Alcohol Dehydrogenase with a Polyion Complex and Redox Polymer for a Bioanode
by Yuki Sakurada, Kouta Takeda, Hiroyuki Ohno and Nobuhumi Nakamura
Catalysts 2017, 7(10), 296; https://doi.org/10.3390/catal7100296 - 03 Oct 2017
Cited by 4 | Viewed by 5193
Abstract
A bioanode for ethanol oxidation was prepared by immobilizing the recombinant pyrroloquinoline quinone (PQQ)-dependent alcohol dehydrogenase from Pseudomonas putida KT 2440 (PpADH) with polyion complex (PIC) and redox polymer. The PIC based on poly-l-lysine (PLL) and poly-l-glutamic acid (PGA) was suitable [...] Read more.
A bioanode for ethanol oxidation was prepared by immobilizing the recombinant pyrroloquinoline quinone (PQQ)-dependent alcohol dehydrogenase from Pseudomonas putida KT 2440 (PpADH) with polyion complex (PIC) and redox polymer. The PIC based on poly-l-lysine (PLL) and poly-l-glutamic acid (PGA) was suitable for immobilizing PpADH on the electrode. PpADH was immobilized using only one redox polymer, aminoferrocene, which was attached to the PGA backbone (PGA-AmFc) on the electrode. The anodic current density at 0.6 V (vs. Ag/AgCl) was 22.6 μA·cm−2. However, when the number of the cycles was increased, the catalytic current drastically decreased. PpADH was immobilized using PGA-AmFc and PIC on the electrode. The anodic current density at 0.5 V (vs. Ag/AgCl) was 47.3 μA·cm−2, and the performance maintained 74% of the initial value after five cycles. This result indicated that the combination of PIC and PGA-AmFc was suitable for the immobilization of PpADH on the electrode. In addition, the long-term stability and catalytic current density were improved by using the large surface area afforded by the gold nanoparticles. Full article
(This article belongs to the Special Issue Biocatalysis and Biotransformations)
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1247 KiB  
Article
Transformation of Sugar Maple Bark through Catalytic Organosolv Pulping
by Georges Koumba-Yoya and Tatjana Stevanovic
Catalysts 2017, 7(10), 294; https://doi.org/10.3390/catal7100294 - 30 Sep 2017
Cited by 12 | Viewed by 3777
Abstract
The catalytic organosolv pulping of sugar maple bark was performed adopting the concept of forest biorefinery in order to transform bark into several valuable products. Our organosolv process, consisting of pre-extracting the lignocellulosic material followed by pulping with ferric chloride as a catalyst, [...] Read more.
The catalytic organosolv pulping of sugar maple bark was performed adopting the concept of forest biorefinery in order to transform bark into several valuable products. Our organosolv process, consisting of pre-extracting the lignocellulosic material followed by pulping with ferric chloride as a catalyst, was applied to sugar maple bark. The pre-extraction step has yielded a mixture of phenolic extractives, applicable as antioxidants. The organosolv pulping of extractives-free sugar maple bark yielded a solid cellulosic pulp (42.3%) and a black liquor containing solubilized bark lignin (24.1%) and products of sugars transformation (22.9% of hemicelluloses), mainly represented by furfural (0.35%) and 5-hydroxymethyl furfural (HMF, 0.74%). The bark cellulosic pulp was determined to be mainly constituted of glucose, with a high residual lignin content, probably related to the protein content of the original bark (containing cambium tissue). The biorefinery approach to the transformation of a solid bark residue into valuable biopolymers (lignin and cellulose) along with phenolic antioxidants from pre-extraction and the HMF derivatives from black liquor (applicable for 2,5-diformylfuran production) is an example of a catalytic process reposing on sustainable engineering and green chemistry concepts. Full article
(This article belongs to the Special Issue Biocatalysis and Biotransformations)
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1180 KiB  
Article
Study of 8 Types of Glutathione Peroxidase Mimics Based on β-Cyclodextrin
by Liwu Wang, Xiaonan Qu, Ying Xie and Shaowu Lv
Catalysts 2017, 7(10), 289; https://doi.org/10.3390/catal7100289 - 28 Sep 2017
Cited by 12 | Viewed by 4152
Abstract
Glutathione peroxidase is key for the removal of H2O2 and other hydroperoxides and therefore, it has an important role in the maintenance of the reactive oxygen species (ROS) metabolic balance in vivo. The native enzymes of the glutathione peroxidase family [...] Read more.
Glutathione peroxidase is key for the removal of H2O2 and other hydroperoxides and therefore, it has an important role in the maintenance of the reactive oxygen species (ROS) metabolic balance in vivo. The native enzymes of the glutathione peroxidase family (GPx) have many defects, such as instability in vitro and poor availability. GPx mimetics has become a topic of considerable interest in artificial enzyme research. Many forms of GPx mimics have been synthesized, by including selenium and tellurium (double-bridged and single-bridged, 2-substituted and 6-substituted) in a mother molecule but differences the GPx mimics enzymatic activity have rarely been compared. We designed and synthesized eight cyclodextrin derivatives and used two types of enzyme assays to determine their activities. The results show that: (a) tellurium-containing GPx mimics have higher activity than that of selenium-containing GPx mimics; (b) dual-bridged mimics have higher activity than bis-bridged mimics; and (c) 2-position modified cyclodextrin has higher activity than 6-position modified cyclodextrin. Full article
(This article belongs to the Special Issue Biocatalysis and Biotransformations)
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1203 KiB  
Article
Polycyclic Ketone Monooxygenase (PockeMO): A Robust Biocatalyst for the Synthesis of Optically Active Sulfoxides
by Gonzalo De Gonzalo, Maximilian J. L. J. Fürst and Marco W. Fraaije
Catalysts 2017, 7(10), 288; https://doi.org/10.3390/catal7100288 - 27 Sep 2017
Cited by 21 | Viewed by 4731
Abstract
A recently discovered, moderately thermostable Baeyer-Villiger monooxygenase, polycyclic ketone monooxygenase (PockeMO), from Thermothelomyces thermophila has been employed as a biocatalyst in a set of asymmetric sulfoxidations. The enzyme was able to catalyze the oxidation of various alkyl aryl sulfides with good selectivities and [...] Read more.
A recently discovered, moderately thermostable Baeyer-Villiger monooxygenase, polycyclic ketone monooxygenase (PockeMO), from Thermothelomyces thermophila has been employed as a biocatalyst in a set of asymmetric sulfoxidations. The enzyme was able to catalyze the oxidation of various alkyl aryl sulfides with good selectivities and moderate to high activities. The biocatalytic performance was able to be further increased by optimizing some reaction parameters, such as the addition of 10% v v−1 of water miscible solvents or toluene, or by performing the conversion at a relatively high temperature (45 °C). PockeMO was found to display an optimum activity at sulfide concentrations of 50 mM, while it can also function at 200 mM. Taken together, the data show that PockeMO can be used as robust biocatalyst for the synthesis of optically active sulfoxides. Full article
(This article belongs to the Special Issue Biocatalysis and Biotransformations)
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2411 KiB  
Article
Enzymatic Systems for Cellulose Acetate Degradation
by Oskar Haske-Cornelius, Alessandro Pellis, Gregor Tegl, Stefan Wurz, Bodo Saake, Roland Ludwig, Andries Sebastian, Gibson S. Nyanhongo and Georg M. Guebitz
Catalysts 2017, 7(10), 287; https://doi.org/10.3390/catal7100287 - 27 Sep 2017
Cited by 40 | Viewed by 10224
Abstract
Cellulose acetate (CA)-based materials, like cigarette filters, contribute to landscape pollution challenging municipal authorities and manufacturers. This study investigates the potential of enzymes to degrade CA and to be potentially incorporated into the respective materials, enhancing biodegradation. Deacetylation studies based on Liquid Chromatography-Mass [...] Read more.
Cellulose acetate (CA)-based materials, like cigarette filters, contribute to landscape pollution challenging municipal authorities and manufacturers. This study investigates the potential of enzymes to degrade CA and to be potentially incorporated into the respective materials, enhancing biodegradation. Deacetylation studies based on Liquid Chromatography-Mass Spectrometry-Time of Flight (LC-MS-TOF), High Performance Liquid Chromatography (HPLC), and spectrophotometric analysis showed that the tested esterases were able to deacetylate the plasticizer triacetin (glycerol triacetate) and glucose pentaacetate (cellulose acetate model compound). The most effective esterases for deacetylation belong to the enzyme family 2 (AXE55, AXE 53, GAE), they deacetylated CA with a degree of acetylation of up to 1.8. A combination of esterases and cellulases showed synergistic effects, the absolute glucose recovery for CA 1.8 was increased from 15% to 28% when an enzymatic deacetylation was performed. Lytic polysaccharide monooxygenase (LPMO), and cellobiohydrolase were able to cleave cellulose acetates with a degree of acetylation of up to 1.4, whereas chitinase showed no activity. In general, the degree of substitution, chain length, and acetyl group distribution were found to affect CA degradation. This study shows that, for a successful enzyme-based deacetylation system, a cocktail of enzymes, which will randomly cleave and generate shorter CA fragments, is the most suitable. Full article
(This article belongs to the Special Issue Biocatalysis and Biotransformations)
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3953 KiB  
Article
Active Site Mimicry of Glutathione Peroxidase by Glutathione Imprinted Selenium-Containing Trypsin
by Yi Huang, Dan-Yang Ge, Hui Zong, Ju-Xin Yin, Xiao-Nan Qu and Shao-Wu Lv
Catalysts 2017, 7(10), 282; https://doi.org/10.3390/catal7100282 - 22 Sep 2017
Cited by 6 | Viewed by 4506
Abstract
In order to overcome the instability of natural glutathione peroxidase (GPx), scientists endeavor to produce GPx mimics. The popular method first uses biological imprinting (BI) to produce the substrate binding sites and then employs chemical mutation (CM) to obtain the catalytic site. However, [...] Read more.
In order to overcome the instability of natural glutathione peroxidase (GPx), scientists endeavor to produce GPx mimics. The popular method first uses biological imprinting (BI) to produce the substrate binding sites and then employs chemical mutation (CM) to obtain the catalytic site. However, BICM has a drawback in that the catalytic site is not clear. Some researchers therefore tried to change the order of the method. These new GPx mimics were prepared by first producing the catalytic site through chemical mutation, and then employing biological imprinting to produce the substrate binding sites (CMBI). It has a clear catalytic site, but its determination of enzyme activity and kinetic analysis are still not elucidated. In this study, we used CMBI to synthesize a GPx mimic using trypsin as the imprinted molecule and GSSG as the template molecule and compared the enzyme activity of the four intermediates (Trypsin-SeO2H (TSeO2H), Trypsin-Se-SG (TSeSG), Imprinted Trypsin-Se-SG (ITSeSG), Cross-linked Imprinted Trypsin-Se-SG (CITSeSG), we analyzed the properties of intermediate products. All values are the means of at least four determinations, ITSeSG was produced from TSeSG through bio-imprinting, the activity of GPx mimics synthesized by CMBI was 5.7 times greater than native GPx, because of bio-imprinting make KmGSH value of the mimics decreased from 4.82 ± 0.27 mM (TSeSG) to 0.52 ± 0.05 mM (ITSeSG). This proves that bio-imprinting is the reason for increased substrate binding capability. Full article
(This article belongs to the Special Issue Biocatalysis and Biotransformations)
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2540 KiB  
Article
A New Homo-Hexamer Mn-Containing Catalase from Geobacillus sp. WCH70
by Hai-Chao Li, Qing Yu, Hui Wang, Xin-Yu Cao, Li Ma and Zheng-Qiang Li
Catalysts 2017, 7(9), 277; https://doi.org/10.3390/catal7090277 - 18 Sep 2017
Cited by 7 | Viewed by 6893
Abstract
Catalase is an effective biocatalyst to degrade hydrogen peroxide to water and oxygen that can serve in textile effluent treatment to remove residual H2O2. Thermostable catalases are needed to withstand both the high temperature and pH of textile wastewater. [...] Read more.
Catalase is an effective biocatalyst to degrade hydrogen peroxide to water and oxygen that can serve in textile effluent treatment to remove residual H2O2. Thermostable catalases are needed to withstand both the high temperature and pH of textile wastewater. We have cloned the Mn-containing catalase gene ACS24898.1 from Geobacillus sp. WCH70, which originated from thermophilic organisms, and expressed it in Escherichia coli in activated form. The recombinant protein has been purified to homogeneity and identified to be a new homo-hexamer Mn-containing catalase. The native molecular mass of the catalase has been measured to be 138 kDa by size-exclusion chromatography. The new enzyme has optimum catalyzed activity at pH 9.0 and a temperature of 75 °C. It is thermostable up to 70 °C for 8 h incubation and maintains 80% and 50% activity, respectively, at 80 °C after 5 h and 90 °C after 1 h. At 75 °C and pH 9.0, the Km is 67.26 mM for substrate H2O2 and the rate of reaction at H2O2 saturation, Vmax, is 75,300 U/mg. The thermophilic and alkaline preferred properties of this new Mn-catalase are valuable features in textile wastewater treatment. Full article
(This article belongs to the Special Issue Biocatalysis and Biotransformations)
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2593 KiB  
Article
Improving the Indigo Carmine Decolorization Ability of a Bacillus amyloliquefaciens Laccase by Site-Directed Mutagenesis
by Jiayi Wang, Lei Lu and Fujuan Feng
Catalysts 2017, 7(9), 275; https://doi.org/10.3390/catal7090275 - 15 Sep 2017
Cited by 49 | Viewed by 9086
Abstract
Indigo carmine is a typical recalcitrant dye which is widely used in textile dyeing processes. Laccases are versatile oxidases showing strong ability to eliminate hazardous dyes from wastewater. However, most laccases require the participation of mediators for efficient decolorization of indigo carmine. Here [...] Read more.
Indigo carmine is a typical recalcitrant dye which is widely used in textile dyeing processes. Laccases are versatile oxidases showing strong ability to eliminate hazardous dyes from wastewater. However, most laccases require the participation of mediators for efficient decolorization of indigo carmine. Here we describe the improvement of the decolorization ability of a bacterial laccase through site-directed mutagenesis. A D501G variant of Bacillus amyloliquefaciens laccase was constructed and overexpressed in Escherichia coli. The laccase activity in the culture supernatant achieved 3374 U·L−1 for the mutant. Compared with the wild-type enzyme, the D501G exhibited better stability and catalytic efficiency. It could decolorize more than 92% of indigo carmine without additional mediators in 5 h at pH 9.0, which was 3.5 times higher than the wild-type laccase. Isatin sulfonic acid was confirmed to be the main product of indigo carmine degradation by UV-vis and LC-MS analyses. Full article
(This article belongs to the Special Issue Biocatalysis and Biotransformations)
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9788 KiB  
Article
Catalytic Characteristics of New Antibacterials Based on Hexahistidine-Containing Organophosphorus Hydrolase
by Olga Maslova, Aysel Aslanli, Nikolay Stepanov, Ilya Lyagin and Elena Efremenko
Catalysts 2017, 7(9), 271; https://doi.org/10.3390/catal7090271 - 14 Sep 2017
Cited by 17 | Viewed by 5481
Abstract
Catalytic characteristics of hexahistidine-containing organophosphorus hydrolase (His6-OPH) and its enzyme-polyelectrolyte complexes with poly-l-glutamic acid or poly-l-aspartic acid (His6-OPH/PLD50), hydrolyzing organophosphorous compounds, and N-acyl homoserine lactones were studied in the presence of various [...] Read more.
Catalytic characteristics of hexahistidine-containing organophosphorus hydrolase (His6-OPH) and its enzyme-polyelectrolyte complexes with poly-l-glutamic acid or poly-l-aspartic acid (His6-OPH/PLD50), hydrolyzing organophosphorous compounds, and N-acyl homoserine lactones were studied in the presence of various antibiotics (ampicillin, gentamicin, kanamycin, and rifampicin). The antibiotics at concentrations below 1 g·L−1 had a negligible inhibiting effect on the His6-OPH activity. Mixed inhibition of His6-OPH was established for higher antibiotic concentrations, and rifampicin was the most potent inhibitor. Stabilization of the His6-OPH activity was observed in the presence of antibiotics at a concentration of 0.2 g·L−1 during exposure at 25–41 °C. Molecular docking of antibiotics to the surface of His6-OPH dimer revealed the antibiotics binding both to the area near active centers of the enzyme subunits and to the region of contact between subunits of the dimer. Such interactions between antibiotics and His6-OPH were verified with Fourier-transform infrared (FTIR) spectroscopy. Considering all the results of the study, the combination of His6-OPH/PLD50 with β-lactam antibiotic ampicillin was established as the optimal one in terms of exhibition and persistence of maximal lactonase activity of the enzyme. Full article
(This article belongs to the Special Issue Biocatalysis and Biotransformations)
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6658 KiB  
Article
Regioselective Synthesis of Lactulose Esters by Candida antarctica and Thermomyces lanuginosus Lipases
by Luis F. Chávez-Flores, Hiram Isaac Beltran, Daniel Arrieta-Baez and Dolores Reyes-Duarte
Catalysts 2017, 7(9), 263; https://doi.org/10.3390/catal7090263 - 03 Sep 2017
Cited by 16 | Viewed by 6009
Abstract
The interest in sugar esters as emulsifiers has been increasing in recent years because they have tunable surfactant properties that depend on the chain length of the fatty acid and the type of the sugar, covering a wide range of hydrophilic-lipophilic balance (HLB). [...] Read more.
The interest in sugar esters as emulsifiers has been increasing in recent years because they have tunable surfactant properties that depend on the chain length of the fatty acid and the type of the sugar, covering a wide range of hydrophilic-lipophilic balance (HLB). In this work, ten biocatalysts were used for the transesterification reaction screening of lactulose, a prebiotic sugar, with vinyl laurate. The reactions were followed by thin layer chromatography (TLC) analysis, identifying two major monoesters mixtures defined as monoester fraction 1 and monoester fraction 2. Candida antarctica lipase B (Novozym 435) produces “monoester fraction 1”, while Thermomyces lanuginosus lipase (Lipozyme® TL IM) and Mucor miehei lipase (Lipozyme®) seem to produce the same “monoester fraction 2”. These three enzymes were selected as model biocatalysts for a kinetic study, and monoester fractions 1 and 2 from Novozym 435 and Lipozyme® TL IM, respectively, were used for product characterization. Monoester fraction 1 contained 86.9% of the major monoester in position 1-O-, and monoester fraction 2 contained 91.4% of 6′-O-. Although these lipases acylated three positions of lactulose, they mainly synthesize a monoester presenting regioselectivity. These results contribute to the study of the chemical structure diversity of biosurfactants to enhance their applications in foods, pharmaceutical products, and cosmetics. Full article
(This article belongs to the Special Issue Biocatalysis and Biotransformations)
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1452 KiB  
Article
Characterization of a Novel Nicotine Hydroxylase from Pseudomonas sp. ZZ-5 That Catalyzes the Conversion of 6-Hydroxy-3-Succinoylpyridine into 2,5-Dihydroxypyridine
by Tao Wei, Jie Zang, Yadong Zheng, Hongzhi Tang, Sheng Huang and Duobin Mao
Catalysts 2017, 7(9), 257; https://doi.org/10.3390/catal7090257 - 31 Aug 2017
Cited by 7 | Viewed by 3662
Abstract
A novel nicotine hydroxylase was isolated from Pseudomonas sp. ZZ-5 (HSPHZZ). The sequence encoding the enzyme was 1206 nucleotides long, and encoded a protein of 401 amino acids. Recombinant HSPHZZ was functionally overexpressed in Escherichia coli BL21-Codon Plus (DE3)-RIL cells [...] Read more.
A novel nicotine hydroxylase was isolated from Pseudomonas sp. ZZ-5 (HSPHZZ). The sequence encoding the enzyme was 1206 nucleotides long, and encoded a protein of 401 amino acids. Recombinant HSPHZZ was functionally overexpressed in Escherichia coli BL21-Codon Plus (DE3)-RIL cells and purified to homogeneity after Ni-NTA affinity chromatography. Liquid chromatography-mass spectrometry (LC-MS) analyses indicated that the enzyme could efficiently catalyze the conversion of 6-hydroxy-3-succinoylpyridine (HSP) into 2,5-dihydroxypyridine (2,5-DHP) and succinic acid in the presence of nicotinamide adenine dinucleotide (NADH) and flavin adenine dinucleotide (FAD). The kinetic constants (Km, kcat, and kcat/Km) of HSPHZZ toward HSP were 0.18 mM, 2.1 s−1, and 11.7 s−1 mM−1, respectively. The optimum temperature, pH, and optimum concentrations of substrate and enzyme for 2,5-DHP production were 30 °C, 8.5, 1.0 mM, and 1.0 μM, respectively. Under optimum conditions, 85.3 mg/L 2,5-DHP was produced in 40 min with a conversion of 74.9%. These results demonstrated that HSPHZZ could be used for the enzymatic production of 2,5-DHP in biotechnology applications. Full article
(This article belongs to the Special Issue Biocatalysis and Biotransformations)
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2352 KiB  
Article
The Kinetic Resolution of Racemic Amines Using a Whole-Cell Biocatalyst Co-Expressing Amine Dehydrogenase and NADH Oxidase
by Hyunwoo Jeon, Sanghan Yoon, Md Murshidul Ahsan, Sihyong Sung, Geon-Hee Kim, Uthayasuriya Sundaramoorthy, Seung-Keun Rhee and Hyungdon Yun
Catalysts 2017, 7(9), 251; https://doi.org/10.3390/catal7090251 - 25 Aug 2017
Cited by 14 | Viewed by 6199
Abstract
Amine dehydrogenase (AmDH) possesses tremendous potential for the synthesis of chiral amines because AmDH catalyzes the asymmetric reductive amination of ketone with high enatioselectivity. Although a reductive application of AmDH is favored in practice, the oxidative route is interesting as well for the [...] Read more.
Amine dehydrogenase (AmDH) possesses tremendous potential for the synthesis of chiral amines because AmDH catalyzes the asymmetric reductive amination of ketone with high enatioselectivity. Although a reductive application of AmDH is favored in practice, the oxidative route is interesting as well for the preparation of chiral amines. Here, the kinetic resolution of racemic amines using AmDH was first extensively studied, and the AmDH reaction was combined with an NADH oxidase (Nox) to regenerate NAD+ and to drive the reaction forward. When the kinetic resolution was carried out with 10 mM rac-2-aminoheptane and 5 mM rac-α-methylbenzylamine (α-MBA) using purified enzymes, the enantiomeric excess (ee) values were less than 26% due to the product inhibition of AmDH by ketone and the inhibition of Nox by the substrate amine. The use of a whole-cell biocatalyst co-expressing AmDH and Nox apparently reduces the substrate and product inhibition, and/or it increases the stability of the enzymes. Fifty millimoles (50 mM) rac-2-aminoheptane and 20 mM rac-α-MBA were successfully resolved into the (S)-form with >99% ee using whole cells. The present study demonstrates the potential of a whole-cell biocatalyst co-expressing AmDH and Nox for the kinetic resolution of racemic amines. Full article
(This article belongs to the Special Issue Biocatalysis and Biotransformations)
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1693 KiB  
Article
Exploiting the Versatility of Aminated Supports Activated with Glutaraldehyde to Immobilize β-galactosidase from Aspergillus oryzae
by Hadjer Zaak, Sara Peirce, Tiago L. De Albuquerque, Mohamed Sassi and Roberto Fernandez-Lafuente
Catalysts 2017, 7(9), 250; https://doi.org/10.3390/catal7090250 - 25 Aug 2017
Cited by 56 | Viewed by 4463
Abstract
The enzyme β-galactosidase from Aspergillus oryzae has been immobilized in aminated (MANAE)-agarose beads via glutaraldehyde chemistry using different strategies. The immobilization on MANAE-supports was first assayed at different pH values (this gave different stabilities to the immobilized enzymes) and further modified with glutaraldehyde. [...] Read more.
The enzyme β-galactosidase from Aspergillus oryzae has been immobilized in aminated (MANAE)-agarose beads via glutaraldehyde chemistry using different strategies. The immobilization on MANAE-supports was first assayed at different pH values (this gave different stabilities to the immobilized enzymes) and further modified with glutaraldehyde. Dramatic drops in activity were found, even using 0.1% (v/v) glutaraldehyde. The use of a support with lower activation permitted to get a final activity of 30%, but stability was almost identical to that of the just adsorbed enzyme. Next, the immobilization on pre-activated glutaraldehyde beads was assayed at pH 5, 7 and 9. At pH 7, full, rapid immobilization and a high expressed enzyme activity were accomplished. At pH 9, some decrease in enzyme activity was observed. Direct covalent immobilization of the enzyme was very slow; even reducing the volume of enzyme/support ratio, the yield was not complete after 24 h. The stability of the biocatalyst using pre-activated supports was about 4–6 folds more stable than that of the enzyme immobilized via ion exchange at pH 5, with small differences among them. Thus, the immobilization of the enzyme at pH 7 at low ionic strength on pre-activated glutaraldehyde supports seems to be the most adequate in terms of activity, stability and immobilization rate. Full article
(This article belongs to the Special Issue Biocatalysis and Biotransformations)
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1035 KiB  
Article
Galactooligosaccharide Production from Pantoea anthophila Strains Isolated from “Tejuino”, a Mexican Traditional Fermented Beverage
by Claudia V. Yañez-Ñeco, Barbara Rodriguez-Colinas, Lorena Amaya-Delgado, Antonio O. Ballesteros, Anne Gschaedler, Francisco J. Plou and Javier Arrizon
Catalysts 2017, 7(8), 242; https://doi.org/10.3390/catal7080242 - 22 Aug 2017
Cited by 18 | Viewed by 4956
Abstract
Two Pantoea anthophila bacterial strains were isolated from “tejuino”, a traditional Mexican beverage, and studied as β-galactosidase producers for galactooligosaccharides synthesis. Using 400 g/L of lactose, 50 °C, and 15 U/mL of β-galactosidase activity with ethanol-permeabilized cells, the maximum galactooligosaccharides (GOS) yield determined [...] Read more.
Two Pantoea anthophila bacterial strains were isolated from “tejuino”, a traditional Mexican beverage, and studied as β-galactosidase producers for galactooligosaccharides synthesis. Using 400 g/L of lactose, 50 °C, and 15 U/mL of β-galactosidase activity with ethanol-permeabilized cells, the maximum galactooligosaccharides (GOS) yield determined by High performance anion exchange chromatography with pulse amperometric detection (HPAEC-PAD) was 136 g/L (34% w/w of total sugars) at 96% of lactose conversion for Bac 55.2 and 145 g/L (36% w/w of total sugars) at 94% of lactose conversion for Bac 69.1. The main synthesized products were the disaccharides allolactose [Gal-β(1 → 6)-Glc] and 6-galactobiose [Gal-β(1 → 6)-Gal], as well as the trisaccharides 3′-galactosyl-lactose [Gal-β(1 → 3)-Gal-β(1 → 4)-Glc], 6-galactotriose [Gal-β(1 → 6)-Gal-β(1 → 6)-Gal], 3′-galactosyl-allolactose [Gal-β(1 → 3)-Gal-β(1 → 6)-Glc], and 6′-galactosyl-lactose [Gal-β(1 → 6)-Gal-β(1 → 4)-Glc]. The β-galactosidases present in both strains showed a high transgalactosylation activity and formed principally β(1 → 3) and β(1 → 6) linkages. Considering the stability and bifidogenic properties of GOS containing such types of bonds, P. anthophila strains Bac 55.2 and Bac 69.1 possess a high potential as novel biocatalysts for prebiotic industrial production. Full article
(This article belongs to the Special Issue Biocatalysis and Biotransformations)
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2150 KiB  
Article
Enzymatic Synthesis of S-Adenosylmethionine Using Immobilized Methionine Adenosyltransferase Variants on the 50-mM Scale
by Weining Niu, Shanshan Cao, Menglin Yang and Le Xu
Catalysts 2017, 7(8), 238; https://doi.org/10.3390/catal7080238 - 17 Aug 2017
Cited by 7 | Viewed by 5125
Abstract
S-adenosylmethionine (SAM), an important metabolite in all living organisms, has been widely used to treat various diseases. To develop a simple and efficient method to produce SAM, an engineered variant of the methionine adenosyltransferase (MAT) from Escherichia coli was investigated for its [...] Read more.
S-adenosylmethionine (SAM), an important metabolite in all living organisms, has been widely used to treat various diseases. To develop a simple and efficient method to produce SAM, an engineered variant of the methionine adenosyltransferase (MAT) from Escherichia coli was investigated for its potential use in the enzymatic synthesis of SAM due to its significantly decreased product inhibition. The recombinant I303V MAT variant was successfully produced at a high level (~800 mg/L) with approximately four-fold higher specific activity than the wild-type MAT. The recombinant I303V MAT was covalently immobilized onto the amino resin and epoxy resin in order to obtain a robust biocatalyst to be used in industrial bioreactors. The immobilized preparation using amino resin exhibited the highest activity coupling yield (~84%), compared with approximately 3% for epoxy resin. The immobilized enzyme was more stable than the soluble enzyme under the reactive conditions, with a half-life of 229.5 h at 37 °C. The KmATP value (0.18 mM) of the immobilized enzyme was ca. two-fold lower than that of the soluble enzyme. Furthermore, the immobilized enzyme showed high operational stability during 10 consecutive 8 h batches, with the substrate adenosine triphosphate (ATP) conversion rate above 95% on the 50-mM scale. Full article
(This article belongs to the Special Issue Biocatalysis and Biotransformations)
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1180 KiB  
Article
l-Amino Acid Production by a Immobilized Double-Racemase Hydantoinase Process: Improvement and Comparison with a Free Protein System
by María José Rodríguez-Alonso, Felipe Rodríguez-Vico, Francisco Javier Las Heras-Vázquez and Josefa María Clemente-Jiménez
Catalysts 2017, 7(6), 192; https://doi.org/10.3390/catal7060192 - 20 Jun 2017
Cited by 7 | Viewed by 5855
Abstract
Protein immobilization is proving to be an environmentally friendly strategy for manufacturing biochemicals at high yields and low production costs. This work describes the optimization of the so-called “double-racemase hydantoinase process,” a system of four enzymes used to produce optically pure l-amino [...] Read more.
Protein immobilization is proving to be an environmentally friendly strategy for manufacturing biochemicals at high yields and low production costs. This work describes the optimization of the so-called “double-racemase hydantoinase process,” a system of four enzymes used to produce optically pure l-amino acids from a racemic mixture of hydantoins. The four proteins were immobilized separately, and, based on their specific activity, the optimal whole relation was determined. The first enzyme, d,l-hydantoinase, preferably hydrolyzes d-hydantoins from d,l-hydantoins to N-carbamoyl-d-amino acids. The remaining l-hydantoins are racemized by the second enzyme, hydantoin racemase, and continue supplying substrate d-hydantoins to the first enzyme. N-carbamoyl-d-amino acid is racemized in turn to N-carbamoyl-l-amino acid by the third enzyme, carbamoyl racemase. Finally, the N-carbamoyl-l-amino acid is transformed to l-amino acid by the fourth enzyme, l-carbamoylase. Therefore, the product of one enzyme is the substrate of another. Perfect coordination of the four activities is necessary to avoid the accumulation of reaction intermediates and to achieve an adequate rate for commercial purposes. The system has shown a broad pH optimum of 7–9, with a maximum activity at 8 and an optimal temperature of 60 °C. Comparison of the immobilized system with the free protein system showed that the reaction velocity increased for the production of norvaline, norleucine, ABA, and homophenylalanine, while it decreased for l-valine and remained unchanged for l-methionine. Full article
(This article belongs to the Special Issue Biocatalysis and Biotransformations)
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846 KiB  
Article
Conversion of Furans by Baeyer-Villiger Monooxygenases
by Hemant Kumar and Marco W. Fraaije
Catalysts 2017, 7(6), 179; https://doi.org/10.3390/catal7060179 - 07 Jun 2017
Cited by 19 | Viewed by 5876
Abstract
Various furans are considered as valuable platform chemicals as they can be derived from plant biomass. Yet, for their exploitation, follow-up chemistry is required. Here we demonstrate that Baeyer-Villiger monooxygenases (BVMOs) can be used as biocatalysts for the selective oxidation of several furans, [...] Read more.
Various furans are considered as valuable platform chemicals as they can be derived from plant biomass. Yet, for their exploitation, follow-up chemistry is required. Here we demonstrate that Baeyer-Villiger monooxygenases (BVMOs) can be used as biocatalysts for the selective oxidation of several furans, including 5-(hydroxymethyl) furfural (HMF) and furfural. A total of 15 different BVMOs were tested for their activity on furfural, which revealed that most of the biocatalysts were active on this aromatic aldehyde. Phenylacetone monooxygenase (PAMO) and a mutant thereof (PAMOM446G) were selected for studying their biocatalytic potential in converting furfural and some other furans. While BVMOs are usually known to form an ester or lactone as a ‘normal’ product by inserting an oxygen atom adjacent to the carbonyl carbon of the substrate, our results reveal that both biocatalysts produce furanoid acids as the main product from the corresponding aldehydes. Altogether, our study shows that BVMOs can be employed for the selective oxidation of furans. Full article
(This article belongs to the Special Issue Biocatalysis and Biotransformations)
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