Enzymes and Biocatalysis

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

Deadline for manuscript submissions: closed (31 March 2022) | Viewed by 43761

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Guest Editor
Department of Seafood Science, National Kaohsiung University of Science and Technology, Kaohsiung 81157, Taiwan
Interests: food analysis, food processing, cellulase; lipase esterification and trans esterification; amylase; enzymatic kinetics; ultrasound-assisted enzymatic reaction; enzyme extraction; biotransformation; saccharification; response surface methodology; artificial neural network; wine fermentation
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Guest Editor

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Guest Editor
Biotechnology Center, National Chung Hsing University, Taichung, Taiwan
Interests: biodiesel; lipid biocatalysis; enzyme technology; bioprocess optimization; supercritical fluid technology; Chinese herb medicine biotechnology
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Department of Marine Environmental Engineering, National Kaohsiung University of Science and Technology, Kaohsiung 81157, Taiwan
Interests: biocatalysis and biochar application; sustainable environment management; advanced oxidative and reductive water purification technology; principles and applications of environmental nanomaterials; sludge and groundwater investigation and remediation; water and wastewater treatment technology and water reuse
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Enzymes are proteins produced by living cells to catalyze a reaction—so-called biocatalysts. Biocatalysis refers to the use of microorganisms and enzymes in chemical reactions, has become increasingly popular, and is frequently applied in the industry, since enzymes are highly specific and high catalytic efficiencies. The biocatalysis system offers several advantages in terms of improved reaction selectivity, reduced energy costs, enhanced reliability, environmental friendliness and sustainability.

In this Special Issue, we welcome original research articles and reviews focused on all aspects of enzymes used for biocatalysis, process optimization, ultrasonic processes, fine chemicals production, enzymatic assisted extraction, enzyme production, biocatalytic processes, environmental protection, bio-reactor, food process, biomass utilization, bioresource application, bio-transformations, enzymology, biological activity, the enzymatic synthesis of value-added chemicals, nanotechnology; environment and biodiversity, bioremediation, etc.

Assoc. Pro Chia-Hung Kuo
Prof. Dr. Chun-Yung Huang
Prof. Dr. Chwen-Jen Shieh
Prof. Dr. Cheng-Di Dong
Guest Editors

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Keywords

  • enzyme production
  • enzyme purification
  • biocatalysis
  • optimization
  • lipase
  • cellulase
  • protease
  • amylase
  • biofuels
  • enzymatic-catalyzed synthesis
  • enzyme immobilization
  • biomass utilization
  • environmental protection
  • glucosidase
  • biotransformation
  • enzymatic kinetics
  • ultrasound-assisted enzymatic reaction
  • bio-reactor
  • enzymatic-assisted extraction
  • experimental design
  • response surface methodology (RSM)
  • artificial neural network (ANN)

Published Papers (14 papers)

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Editorial

Jump to: Research, Review

6 pages, 229 KiB  
Editorial
Enzymes and Biocatalysis
by Chia-Hung Kuo, Chun-Yung Huang, Chwen-Jen Shieh and Cheng-Di Dong
Catalysts 2022, 12(9), 993; https://doi.org/10.3390/catal12090993 - 02 Sep 2022
Cited by 6 | Viewed by 2030
Abstract
Enzymes, also known as biocatalysts, are proteins produced by living cells and found in a wide range of species, including animals, plants, and microorganisms [...] Full article
(This article belongs to the Special Issue Enzymes and Biocatalysis)

Research

Jump to: Editorial, Review

9 pages, 1422 KiB  
Communication
Rational Design of a Calcium-Independent Trypsin Variant
by Andreas H. Simon, Sandra Liebscher, Ariunkhur Kattner, Christof Kattner and Frank Bordusa
Catalysts 2022, 12(9), 990; https://doi.org/10.3390/catal12090990 - 01 Sep 2022
Cited by 2 | Viewed by 2347
Abstract
Trypsin is a long-known serine protease widely used in biochemical, analytical, biotechnological, or biocatalytic applications. The high biotechnological potential is based on its high catalytic activity, substrate specificity, and catalytic robustness in non-physiological reaction conditions. The latter is mainly due to its stable [...] Read more.
Trypsin is a long-known serine protease widely used in biochemical, analytical, biotechnological, or biocatalytic applications. The high biotechnological potential is based on its high catalytic activity, substrate specificity, and catalytic robustness in non-physiological reaction conditions. The latter is mainly due to its stable protein fold, to which six intramolecular disulfide bridges make a significant contribution. Although trypsin does not depend on cofactors, it essentially requires the binding of calcium ions to its calcium-binding site to obtain complete enzymatic activity and stability. This behavior is inevitably associated with a limitation of the enzyme’s applicability. To make trypsin intrinsically calcium-independent, we removed the native calcium-binding site and replaced it with another disulfide bridge. The resulting stabilized apo-trypsin (aTn) retains full catalytic activity as proven by enzyme kinetics. Studies using Ellmann’s reagent further prove that the two inserted cysteines at positions Glu70 and Glu80 are in their oxidized state, creating the desired functional disulfide bond. Furthermore, aTn is independent of calcium ions, possesses increased thermal and functional stability, and significantly reduced autolysis compared to wildtype trypsin. Finally, we confirmed our experimental data by solving the X-ray crystal structure of aTn. Full article
(This article belongs to the Special Issue Enzymes and Biocatalysis)
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14 pages, 1826 KiB  
Article
Continuous Production of DHA and EPA Ethyl Esters via Lipase-Catalyzed Transesterification in an Ultrasonic Packed-Bed Bioreactor
by Chia-Hung Kuo, Mei-Ling Tsai, Hui-Min David Wang, Yung-Chuan Liu, Chienyan Hsieh, Yung-Hsiang Tsai, Cheng-Di Dong, Chun-Yung Huang and Chwen-Jen Shieh
Catalysts 2022, 12(4), 404; https://doi.org/10.3390/catal12040404 - 06 Apr 2022
Cited by 6 | Viewed by 1725
Abstract
Ethyl esters of omega-3 fatty acids are active pharmaceutical ingredients used for the reduction in triglycerides in the treatment of hyperlipidemia. Herein, an ultrasonic packed-bed bioreactor was developed for continuous production of docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) ethyl esters from DHA+EPA [...] Read more.
Ethyl esters of omega-3 fatty acids are active pharmaceutical ingredients used for the reduction in triglycerides in the treatment of hyperlipidemia. Herein, an ultrasonic packed-bed bioreactor was developed for continuous production of docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) ethyl esters from DHA+EPA concentrate and ethyl acetate (EA) using an immobilized lipase, Novozym® 435, as a biocatalyst. A three-level–two-factor central composite design combined with a response surface methodology (RSM) was employed to evaluate the packed-bed bioreactor with or without ultrasonication on the conversion of DHA + EPA ethyl ester. The highest conversion of 99% was achieved with ultrasonication at the condition of 1 mL min−1 flow rate and 100 mM DHA + EPA concentration. Our results also showed that the ultrasonic packed-bed bioreactor has a higher external mass transfer coefficient and a lower external substrate concentration on the surface of the immobilized enzyme. The effect of ultrasound was also demonstrated by a kinetic model in the batch reaction that the specificity constant (V′max/K2) in the ultrasonic bath was 8.9 times higher than that of the shaking bath, indicating the ultrasonication increased the affinity between enzymes and substrates and, therefore, increasing reaction rate. An experiment performed under the highest conversion conditions showed that the enzyme in the bioreactor remained stable at least for 5 days and maintained a 98% conversion. Full article
(This article belongs to the Special Issue Enzymes and Biocatalysis)
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13 pages, 1062 KiB  
Article
Effects of Soil Surface Chemistry on Adsorption and Activity of Urease from a Crude Protein Extract: Implications for Biocementation Applications
by Rayla Pinto Vilar and Kaoru Ikuma
Catalysts 2022, 12(2), 230; https://doi.org/10.3390/catal12020230 - 18 Feb 2022
Cited by 2 | Viewed by 1748
Abstract
In the bacterial enzyme-induced calcite precipitation (BEICP) technique for biocementation, the spatial distribution of adsorbed and catalytically active urease dictates the location where calcium carbonate precipitation and resulting cementation will occur. This study investigated the relationships between the amount of urease and total [...] Read more.
In the bacterial enzyme-induced calcite precipitation (BEICP) technique for biocementation, the spatial distribution of adsorbed and catalytically active urease dictates the location where calcium carbonate precipitation and resulting cementation will occur. This study investigated the relationships between the amount of urease and total bacterial proteins adsorbed, the retained enzymatic activity of adsorbed urease, and the overall loss of activity upon adsorption, and how these relationships are influenced by changes in soil surface chemistry. In soils with hydrophobic contents higher than 20% (w/w) ratio, urease was preferentially adsorbed compared to the total amount of proteins present in the crude bacterial protein extract. Conversely, adsorption of urease onto silica sand and soil mixtures, including iron-coated sand, was much lower compared to the total proteins. Higher levels of urease activity were retained in hydrophobic-containing samples, with urease activity decreasing with lower hydrophobic content. These observations suggest that the surface manipulation of soils, such as treatments to add hydrophobicity to soil surfaces, can potentially be used to increase the activity of adsorbed urease to improve biocementation outcomes. Full article
(This article belongs to the Special Issue Enzymes and Biocatalysis)
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18 pages, 3587 KiB  
Article
An Alkalothermophilic Amylopullulanase from the Yeast Clavispora lusitaniae ABS7: Purification, Characterization and Potential Application in Laundry Detergent
by Scheherazed Dakhmouche Djekrif, Leila Bennamoun, Fatima Zohra Kenza Labbani, Amel Ait Kaki, Tahar Nouadri, André Pauss, Zahia Meraihi and Louisa Gillmann
Catalysts 2021, 11(12), 1438; https://doi.org/10.3390/catal11121438 - 26 Nov 2021
Cited by 14 | Viewed by 2118
Abstract
In the present study, α-amylase and pullulanase from Clavispora lusitaniae ABS7 isolated from wheat seeds were studied. The gel filtration and ion-exchange chromatography revealed the presence of α-amylase and pullulanase activities in the same fraction with yields of 23.88% and 21.11%, respectively. SDS-PAGE [...] Read more.
In the present study, α-amylase and pullulanase from Clavispora lusitaniae ABS7 isolated from wheat seeds were studied. The gel filtration and ion-exchange chromatography revealed the presence of α-amylase and pullulanase activities in the same fraction with yields of 23.88% and 21.11%, respectively. SDS-PAGE showed a single band (75 kDa), which had both α-amylase (independent of Ca2+) and pullulanase (a calcium metalloenzyme) activities. The products of the enzymatic reaction on pullulan were glucose, maltose, and maltotriose, whereas the conversion of starch produced glucose and maltose. The α-amylase and pullulanase had pH optima at 9 and temperature optima at 75 and 80 °C, respectively. After heat treatment at 100 °C for 180 min, the pullulanase retained 42% of its initial activity, while α-amylase maintained only 38.6%. The cations Zn2+, Cu2+, Na+, and Mn2+ increased the α-amylase activity. Other cations Hg2+, Mg2+, and Ca2+ were stimulators of pullulanase. Urea and Tween 80 inhibited both enzymes, whereas EDTA only inhibited pullulanase. In addition, the amylopullulanase retained its activity in the presence of various commercial laundry detergents. The performance of the alcalothermostable enzyme of Clavispora lusitaniae ABS7 qualified it for the industrial use, particularly in detergents, since it had demonstrated an excellent stability and compatibility with the commercial laundry detergents. Full article
(This article belongs to the Special Issue Enzymes and Biocatalysis)
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16 pages, 1702 KiB  
Article
Application Potential of Cyanide Hydratase from Exidia glandulosa: Free Cyanide Removal from Simulated Industrial Effluents
by Anastasia Sedova, Lenka Rucká, Pavla Bojarová, Michaela Glozlová, Petr Novotný, Barbora Křístková, Miroslav Pátek and Ludmila Martínková
Catalysts 2021, 11(11), 1410; https://doi.org/10.3390/catal11111410 - 21 Nov 2021
Cited by 6 | Viewed by 2231
Abstract
Industries such as mining, cokemaking, (petro)chemical and electroplating produce effluents that contain free cyanide (fCN = HCN + CN). Currently, fCN is mainly removed by (physico)chemical methods or by biotreatment with activated sludge. Cyanide hydratases (CynHs) (EC 4.2.1.66), which convert fCN [...] Read more.
Industries such as mining, cokemaking, (petro)chemical and electroplating produce effluents that contain free cyanide (fCN = HCN + CN). Currently, fCN is mainly removed by (physico)chemical methods or by biotreatment with activated sludge. Cyanide hydratases (CynHs) (EC 4.2.1.66), which convert fCN to the much less toxic formamide, have been considered for a mild approach to wastewater decyanation. However, few data are available to evaluate the application potential of CynHs. In this study, we used a new CynH from Exidia glandulosa (protein KZV92691.1 designated NitEg by us), which was overproduced in Escherichia coli. The purified NitEg was highly active for fCN with 784 U/mg protein, kcat 927/s and kcat/KM 42/s/mM. It exhibited optimal activities at pH approximately 6–9 and 40–45 °C. It was quite stable in this pH range, and retained approximately 40% activity at 37 °C after 1 day. Silver and copper ions (1 mM) decreased its activity by 30–40%. The removal of 98–100% fCN was achieved for 0.6–100 mM fCN. Moreover, thiocyanate, sulfide, ammonia or phenol added in amounts typical of industrial effluents did not significantly reduce the fCN conversion, while electroplating effluents may need to be diluted due to high fCN and metal content. The ease of preparation of NitEg, its high specific activity, robustness and long shelf life make it a promising biocatalyst for the detoxification of fCN. Full article
(This article belongs to the Special Issue Enzymes and Biocatalysis)
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13 pages, 2529 KiB  
Article
Effects of Lower Temperature on Expression and Biochemical Characteristics of HCV NS3 Antigen Recombinant Protein
by Chen-Ji Huang, Hwei-Ling Peng, Anil Kumar Patel, Reeta Rani Singhania, Cheng-Di Dong and Chih-Yu Cheng
Catalysts 2021, 11(11), 1297; https://doi.org/10.3390/catal11111297 - 27 Oct 2021
Cited by 8 | Viewed by 4284
Abstract
The nonstructural antigen protein 3 of the hepatitis C virus (HCV NS3), commonly-used for HCV ELISA diagnosis, possesses protease and helicase activities. To prevent auto-degradation, a truncated NS3 protein was designed by removing the protease domain. Firstly, it was overexpressed in E. coli [...] Read more.
The nonstructural antigen protein 3 of the hepatitis C virus (HCV NS3), commonly-used for HCV ELISA diagnosis, possesses protease and helicase activities. To prevent auto-degradation, a truncated NS3 protein was designed by removing the protease domain. Firstly, it was overexpressed in E. coli by IPTG induction under two different temperatures (25 and 37 °C), and purified using affinity chromatography to attain homogeneity above 90%. The molecular mass of purified protein was determined to be approx. 55 kDa. While lowering the temperature from 37 to 25 °C, the yield of the soluble fraction of HCV NS3 was increased from 4.15 to 11.1 mgL−1 culture, which also improved the antigenic activity and specificity. The protein stability was investigated after long-term storage (for 6 months at −20 °C) revealed no loss of activity, specificity, or antigenic efficacy. A thermal stability study on both freshly produced and stored HCV NS3 fractions at both temperatures showed that the unfolding curve profile properly obey the three-state unfolding mechanism. In the first transition phase, the midpoints of the thermal denaturation of fresh NS3 produced at 37 °C and 25 °C, and that produced after long-term storage at 37 °C and 25 °C, were 59.7 °C, 59.1 °C, 55.5 °C, and 57.8 °C, respectively. Microplates coated with the fresh NS3 produced at 25 °C or at 37 °C that were used for the HCV ELISA test and the diagnosis outcome were compared with two commercial kits—Abbott HCV EIA 2.0 and Ortho HCV EIA 3.0. Results indicated that the specificity of the HCV NS3 produced fresh at 25 °C was higher than that of the fresh one at 37 °C, hence showing potential for application in HCV ELISA diagnosis. Full article
(This article belongs to the Special Issue Enzymes and Biocatalysis)
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10 pages, 937 KiB  
Article
Gordonia hydrophobica Nitrile Hydratase for Amide Preparation from Nitriles
by Birgit Grill, Melissa Horvat, Helmut Schwab, Ralf Gross, Kai Donsbach and Margit Winkler
Catalysts 2021, 11(11), 1287; https://doi.org/10.3390/catal11111287 - 26 Oct 2021
Cited by 2 | Viewed by 1901
Abstract
The active pharmaceutical ingredient levetiracetam has anticonvulsant properties and is used to treat epilepsies. Herein, we describe the enantioselective preparation of the levetiracetam precursor 2-(pyrrolidine-1-yl)butanamide by enzymatic dynamic kinetic resolution with a nitrile hydratase enzyme. A rare representative of the family of iron-dependent [...] Read more.
The active pharmaceutical ingredient levetiracetam has anticonvulsant properties and is used to treat epilepsies. Herein, we describe the enantioselective preparation of the levetiracetam precursor 2-(pyrrolidine-1-yl)butanamide by enzymatic dynamic kinetic resolution with a nitrile hydratase enzyme. A rare representative of the family of iron-dependent nitrile hydratases from Gordonia hydrophobica (GhNHase) was evaluated for its potential to form 2-(pyrrolidine-1-yl)butanamide in enantioenriched form from the three small, simple molecules, namely, propanal, pyrrolidine and cyanide. The yield and the enantiomeric excess (ee) of the product are determined most significantly by the substrate concentrations, the reaction pH and the biocatalyst amount. GhNHase is also active for the hydration of other nitriles, in particular for the formation of N-heterocyclic amides such as nicotinamide, and may therefore be a tool for the preparation of various APIs. Full article
(This article belongs to the Special Issue Enzymes and Biocatalysis)
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11 pages, 2444 KiB  
Article
Phenylalanine, Tyrosine, and DOPA Are bona fide Substrates for Bambusa oldhamii BoPAL4
by Chun-Yen Hsieh, Yi-Hao Huang, Hui-Hsuan Yeh, Pei-Yu Hong, Che-Jen Hsiao and Lu-Sheng Hsieh
Catalysts 2021, 11(11), 1263; https://doi.org/10.3390/catal11111263 - 20 Oct 2021
Cited by 10 | Viewed by 2281
Abstract
Phenylalanine ammonia-lyase (PAL) links the plant primary and secondary metabolisms, and its product, trans-cinnamic acid, is derived into thousands of diverse phenylpropanoids. Bambusa oldhamii BoPAL4 has broad substrate specificity using L-phenylalanine, L-tyrosine, and L-3,4-dihydroxy phenylalanine (L-DOPA) as substrates to yield trans-cinnamic [...] Read more.
Phenylalanine ammonia-lyase (PAL) links the plant primary and secondary metabolisms, and its product, trans-cinnamic acid, is derived into thousands of diverse phenylpropanoids. Bambusa oldhamii BoPAL4 has broad substrate specificity using L-phenylalanine, L-tyrosine, and L-3,4-dihydroxy phenylalanine (L-DOPA) as substrates to yield trans-cinnamic acid, p-coumaric acid, and caffeic acid, respectively. The optimum reaction pH of BoPAL4 for three substrates was measured at 9.0, 8.5, and 9.0, respectively. The optimum reaction temperatures of BoPAL4 for three substrates were obtained at 50, 60, and 40 °C, respectively. The Km values of BoPAL4 for three substrates were 2084, 98, and 956 μM, respectively. The kcat values of BoPAL4 for three substrates were 1.44, 0.18, and 0.06 σ−1, respectively. The major substrate specificity site mutant, BoPAL4-H123F, showed better affinity toward L-phenylalanine by decreasing its Km value to 640 μM and increasing its kcat value to 1.87 s−1. In comparison to wild-type BoPAL4, the specific activities of BoPAL4-H123F using L-tyrosine and L-DOPA as substrates retained 5.4% and 17.8% residual activities. Therefore, L-phenylalanine, L-tyrosine, and L-DOPA are bona fide substrates for BoPAL4. Full article
(This article belongs to the Special Issue Enzymes and Biocatalysis)
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17 pages, 2046 KiB  
Article
Utilization of Clay Materials as Support for Aspergillus japonicus Lipase: An Eco-Friendly Approach
by Daniela Remonatto, Bárbara Ribeiro Ferrari, Juliana Cristina Bassan, Cassamo Ussemane Mussagy, Valéria de Carvalho Santos-Ebinuma and Ariela Veloso de Paula
Catalysts 2021, 11(10), 1173; https://doi.org/10.3390/catal11101173 - 28 Sep 2021
Cited by 13 | Viewed by 1741
Abstract
Lipase is an important group of biocatalysts, which combines versatility and specificity, and can catalyze several reactions when applied in a high amount of industrial processes. In this study, the lipase produced by Aspergillus japonicus under submerged cultivation, was immobilized by physical adsorption, [...] Read more.
Lipase is an important group of biocatalysts, which combines versatility and specificity, and can catalyze several reactions when applied in a high amount of industrial processes. In this study, the lipase produced by Aspergillus japonicus under submerged cultivation, was immobilized by physical adsorption, using clay supports, namely, diatomite, vermiculite, montmorillonite KSF (MKSF) and kaolinite. Besides, the immobilized and free enzyme was characterized, regarding pH, temperature and kinetic parameters. The most promising clay support was MKSF that presented 69.47% immobilization yield and hydrolytic activity higher than the other conditions studied (270.7 U g−1). The derivative produced with MKSF showed high stability at pH and temperature, keeping 100% of its activity throughout 12 h of incubation in the pH ranges between 4.0 and 9.0 and at a temperature from 30 to 50 °C. In addition, the immobilized lipase on MKSF support showed an improvement in the catalytic performance. The study shows the potential of using clays as support to immobilized lipolytic enzymes by adsorption method, which is a simple and cost-effective process. Full article
(This article belongs to the Special Issue Enzymes and Biocatalysis)
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16 pages, 1761 KiB  
Article
Use of a Sequential Fermentation Method for the Production of Aspergillus tamarii URM4634 Protease and a Kinetic/Thermodynamic Study of the Enzyme
by Rodrigo Lira de Oliveira, Emiliana de Souza Claudino, Attilio Converti and Tatiana Souza Porto
Catalysts 2021, 11(8), 963; https://doi.org/10.3390/catal11080963 - 11 Aug 2021
Cited by 5 | Viewed by 2162
Abstract
Microbial proteases are commonly produced by submerged (SmF) or solid-state fermentation (SSF), whose combination results in an unconventional method, called sequential fermentation (SF), which has already been used only to produce cellulolytic enzymes. In this context, the aim of the present study was [...] Read more.
Microbial proteases are commonly produced by submerged (SmF) or solid-state fermentation (SSF), whose combination results in an unconventional method, called sequential fermentation (SF), which has already been used only to produce cellulolytic enzymes. In this context, the aim of the present study was the development of a novel SF method for protease production using wheat bran as a substrate. Moreover, the kinetic and thermodynamic parameters of azocasein hydrolysis were estimated, thus providing a greater understanding of the catalytic reaction. In SF, an approximately 9-fold increase in protease activity was observed compared to the conventional SmF method. Optimization of glucose concentration and medium volume by statistical means allowed us to achieve a maximum protease activity of 180.17 U mL−1. The obtained enzyme had an optimum pH and temperature of 7.0 and 50 °C, respectively. Kinetic and thermodynamic parameters highlighted that such a neutral protease is satisfactorily thermostable at 50 °C, a temperature commonly used in many applications in the food industry. The results obtained suggested not only that SF could be a promising alternative to produce proteases, but also that it could be adapted to produce several other enzymes. Full article
(This article belongs to the Special Issue Enzymes and Biocatalysis)
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20 pages, 3126 KiB  
Article
Two Novel, Flavin-Dependent Halogenases from the Bacterial Consortia of Botryococcus braunii Catalyze Mono- and Dibromination
by Pia R. Neubauer, Olga Blifernez-Klassen, Lara Pfaff, Mohamed Ismail, Olaf Kruse and Norbert Sewald
Catalysts 2021, 11(4), 485; https://doi.org/10.3390/catal11040485 - 10 Apr 2021
Cited by 5 | Viewed by 3545
Abstract
Halogen substituents often lead to a profound effect on the biological activity of organic compounds. Flavin-dependent halogenases offer the possibility of regioselective halogenation at non-activated carbon atoms, while employing only halide salts and molecular oxygen. However, low enzyme activity, instability, and narrow substrate [...] Read more.
Halogen substituents often lead to a profound effect on the biological activity of organic compounds. Flavin-dependent halogenases offer the possibility of regioselective halogenation at non-activated carbon atoms, while employing only halide salts and molecular oxygen. However, low enzyme activity, instability, and narrow substrate scope compromise the use of enzymatic halogenation as an economical and environmentally friendly process. To overcome these drawbacks, it is of tremendous interest to identify novel halogenases with high enzymatic activity and novel substrate scopes. Previously, Neubauer et al. developed a new hidden Markov model (pHMM) based on the PFAM tryptophan halogenase model, and identified 254 complete and partial putative flavin-dependent halogenase genes in eleven metagenomic data sets. In the present study, the pHMM was used to screen the bacterial associates of the Botryococcus braunii consortia (PRJEB21978), leading to the identification of several putative, flavin-dependent halogenase genes. Two of these new halogenase genes were found in one gene cluster of the Botryococcus braunii symbiont Sphingomonas sp. In vitro activity tests revealed that both heterologously expressed enzymes are active flavin-dependent halogenases able to halogenate indole and indole derivatives, as well as phenol derivatives, while preferring bromination over chlorination. Interestingly, SpH1 catalyses only monohalogenation, while SpH2 can catalyse both mono- and dihalogenation for some substrates. Full article
(This article belongs to the Special Issue Enzymes and Biocatalysis)
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Review

Jump to: Editorial, Research

43 pages, 4819 KiB  
Review
Metagenomic Approaches as a Tool to Unravel Promising Biocatalysts from Natural Resources: Soil and Water
by Joana Sousa, Sara C. Silvério, Angela M. A. Costa and Ligia R. Rodrigues
Catalysts 2022, 12(4), 385; https://doi.org/10.3390/catal12040385 - 30 Mar 2022
Cited by 7 | Viewed by 3492
Abstract
Natural resources are considered a promising source of microorganisms responsible for producing biocatalysts with great relevance in several industrial areas. However, a significant fraction of the environmental microorganisms remains unknown or unexploited due to the limitations associated with their cultivation in the laboratory [...] Read more.
Natural resources are considered a promising source of microorganisms responsible for producing biocatalysts with great relevance in several industrial areas. However, a significant fraction of the environmental microorganisms remains unknown or unexploited due to the limitations associated with their cultivation in the laboratory through classical techniques. Metagenomics has emerged as an innovative and strategic approach to explore these unculturable microorganisms through the analysis of DNA extracted from environmental samples. In this review, a detailed discussion is presented on the application of metagenomics to unravel the biotechnological potential of natural resources for the discovery of promising biocatalysts. An extensive bibliographic survey was carried out between 2010 and 2021, covering diverse metagenomic studies using soil and/or water samples from different types and locations. The review comprises, for the first time, an overview of the worldwide metagenomic studies performed in soil and water and provides a complete and global vision of the enzyme diversity associated with each specific environment. Full article
(This article belongs to the Special Issue Enzymes and Biocatalysis)
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21 pages, 388 KiB  
Review
Exogenous Enzymes as Zootechnical Additives in Animal Feed: A Review
by Brianda Susana Velázquez-De Lucio, Edna María Hernández-Domínguez, Matilde Villa-García, Gerardo Díaz-Godínez, Virginia Mandujano-Gonzalez, Bethsua Mendoza-Mendoza and Jorge Álvarez-Cervantes
Catalysts 2021, 11(7), 851; https://doi.org/10.3390/catal11070851 - 15 Jul 2021
Cited by 30 | Viewed by 7785
Abstract
Enzymes are widely used in the food industry. Their use as a supplement to the raw material for animal feed is a current research topic. Although there are several studies on the application of enzyme additives in the animal feed industry, it is [...] Read more.
Enzymes are widely used in the food industry. Their use as a supplement to the raw material for animal feed is a current research topic. Although there are several studies on the application of enzyme additives in the animal feed industry, it is necessary to search for new enzymes, as well as to utilize bioinformatics tools for the design of specific enzymes that work in certain environmental conditions and substrates. This will allow the improvement of the productive parameters in animals, reducing costs and making the processes more efficient. Technological needs have considered these catalysts as essential in many industrial sectors and research is constantly being carried out to optimize their use in those processes. This review describes the enzymes used in animal nutrition, their mode of action, their production and new sources of production as well as studies on different animal models to evaluate their effect on the productive performance intended for the production of animal feed. Full article
(This article belongs to the Special Issue Enzymes and Biocatalysis)
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