Special Issue "Immobilized Biocatalysts"

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

Deadline for manuscript submissions: closed (31 March 2018)

Special Issue Editor

Guest Editor
Prof. Dr. Peter Grunwald

University of Hamburg, Department of Physical Chemistry, Grindelallee 117, 20146 Hamburg, Germany
Website | E-Mail
Interests: biocatalysis; enzymatic analysis; Environmental biotechnology

Special Issue Information

Dear Colleagues,

Biocatalysts—single enzymes or whole cells—have gained increasing importance in the last few decades as green alternatives to their chemical counterparts for a variety of industrial processes. They catalyze reactions with the advantage of superior chemo-, regio-, and stereo-specificity at mild conditions, thereby avoiding the production of larger amounts of waste. To prevent spoiling of the resulting products with protein the biocatalysts should be employed in an immobilized form. In contrast to the application of soluble enzymes, they enable a higher volume specific biocatalyst loading together with simplified downstream processing. In addition, they can be reused tantamount to reducing cost contribution to the final product. Immobilization may also contribute to an enhanced storage and operational stability compared to soluble biocatalysts.

Immobilized biocatalysts are—apart from application in the chemical/pharmaceutical industry—used as biosensors, in medical diagnoses, genomics and genome sequencing (next generation sequencing), for protein microarrays (tracking interactions and activities of proteins, drug screening, etc.), or enzyme biocomputing.

The activity (efficiency) of an immobilized biocatalyst depends on various properties of the carrier material such as particle size and shape, its chemical nature, density, porosity (mass transfer limitation of the compounds involved), pore-size distribution or the mechanical strength. In addition, suited immobilization supports aside from bearing functional groups on their surface should be hydrophilic, biocompatible, resistant to microbial attack, and readily available at a low cost. They are of inorganic or organic origin and include natural and synthetic polymers. Bioinspired scaffolds and nanostructured materials (nanoparticles (paramagnetic), nanofibers, nanotubes, graphene, nanocomposites) are also used for enzyme immobilization.

Traditional immobilization techniques comprise adsorption, covalent binding, crosslinking, and entrapment. Moreover, immobilization and chemical modification may be coupled with site-directed mutagenesis, and nanobiocatalysts are generated by biological assembly methods. For covalent, site-specific immobilization several chemical and enzymatic approaches have proven. A variety of surface analysis technologies exist to control enzyme immobilization.

Prof. Dr. Peter Grunwald
Guest Editor

Manuscript Submission Information

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

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

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1300 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

  • Immobilized Biocatalysts, application areas (industrial production of goods and chemicals, pharmaceuticals, biofuel) analytics, diagnoses, microarrays, biocomputing, biofuel cells, bioactive coatings
  • Immobilization techniques, -traditional, site-specific protein immobilization, enzyme-mediated immobilization, biological assembly methods, cascade reactions, protein scaffolds, self-assembly of enzyme nanostructures, multi-enzyme immobilization, immobilization and site-directed mutagenesis
  • Immobilization supports, -properties, (quantum dots, magnetic nanoparticles, nanorods, nanotubes, nanofibres, nanocomposites
  • inorganic and organic materials, natural and synthetic polymers), biosynthesis of nanoparticles
  • surface analysis technologies (atomic force spectroscopy, FRET, BRET, TEM, SPR, and others)
  • kinetics of immobilized biocatalysts.

Published Papers (27 papers)

View options order results:
result details:
Displaying articles 1-27
Export citation of selected articles as:

Research

Jump to: Review

Open AccessArticle Immobilization of an Antarctic Pseudomonas AMS8 Lipase for Low Temperature Ethyl Hexanoate Synthesis
Catalysts 2018, 8(6), 234; https://doi.org/10.3390/catal8060234
Received: 31 March 2018 / Revised: 28 April 2018 / Accepted: 2 May 2018 / Published: 4 June 2018
PDF Full-text (3887 KB) | HTML Full-text | XML Full-text
Abstract
The demand for synthetic flavor ester is high, especially in the food, beverage, and cosmetic and pharmaceutical industries. It is derived from the reaction between a short-chain fatty acid and alcohol. Lipases from Antarctic bacteria have gained huge interest in the industry due
[...] Read more.
The demand for synthetic flavor ester is high, especially in the food, beverage, and cosmetic and pharmaceutical industries. It is derived from the reaction between a short-chain fatty acid and alcohol. Lipases from Antarctic bacteria have gained huge interest in the industry due to its ability react at low temperatures. The use of immobilization enzymes is one of the methods that can improve the stability of the enzyme. The current work encompasses the low temperature enzymatic synthesis of ethyl hexanoate by direct esterification of ethanol with hexanoic acid in a toluene and solvent-free system. The effects of various reaction parameters such as the organic solvent, temperature, time, substrate, substrate ratio and concentration, enzyme concentration on ethyl hexanoate synthesis were tested. Several matrices were used for immobilization and comparisons of the efficiency of immobilized enzyme with free enzyme in the synthesis of flavor ester were conducted. Ester production was optimally synthesized at 20 °C in both systems— immobilized and free enzyme. A 69% ester conversion rate was achieved after a two-hour incubation in toluene, compared to 47% in a solvent-free system for free enzyme. Immobilized AMS8 lipase showed a higher conversion of ester in toluene with respect to free-solvents, from 80% to 59%, respectively. Immobilized enzymes showed enhancement to the stability of the enzyme in the presence of the organic solvent. The development of AMS8 lipase as an immobilized biocatalyst demonstrates great potential as a cost-effective enzyme for biocatalysis and biotransformation in the food industry. Full article
(This article belongs to the Special Issue Immobilized Biocatalysts)
Figures

Figure 1

Open AccessArticle Immobilization of the β-fructofuranosidase from Xanthophyllomyces dendrorhous by Entrapment in Polyvinyl Alcohol and Its Application to Neo-Fructooligosaccharides Production
Catalysts 2018, 8(5), 201; https://doi.org/10.3390/catal8050201
Received: 21 April 2018 / Revised: 7 May 2018 / Accepted: 9 May 2018 / Published: 11 May 2018
PDF Full-text (1963 KB) | HTML Full-text | XML Full-text
Abstract
The β-fructofuranosidase (Xd-INV) from the basidiomycota yeast Xanthophyllomyces dendrorhous (formerly Phaffia rhodozyma) is unique in its ability to synthesize neo- fructooligosaccharides (neo-FOS). In order to facilitate its industrial application, the recombinant enzyme expressed in Pichia pastoris (pXd-INV) was immobilized by entrapment in
[...] Read more.
The β-fructofuranosidase (Xd-INV) from the basidiomycota yeast Xanthophyllomyces dendrorhous (formerly Phaffia rhodozyma) is unique in its ability to synthesize neo- fructooligosaccharides (neo-FOS). In order to facilitate its industrial application, the recombinant enzyme expressed in Pichia pastoris (pXd-INV) was immobilized by entrapment in polyvinyl alcohol (PVA) hydrogels. The encapsulation efficiency exceeded 80%. The PVA lenticular particles of immobilized pXd-INV were stable up to approximately 40 °C. Using 600 g/L sucrose, the immobilized biocatalyst synthesized 18.9% (w/w) FOS (59.1 g/L of neokestose, 30.2 g/L of 1-kestose, 11.6 g/L of neonystose and 12.6 g/L of blastose). The operational stability of PVA-immobilized biocatalyst was assayed in a batch reactor at 30 °C. The enzyme preserved its initial activity during at least 7 cycles of 26 h. Full article
(This article belongs to the Special Issue Immobilized Biocatalysts)
Figures

Figure 1

Open AccessArticle One-Pot, One-Step Production of Dietary Nucleotides by Magnetic Biocatalysts
Catalysts 2018, 8(5), 184; https://doi.org/10.3390/catal8050184
Received: 6 April 2018 / Revised: 25 April 2018 / Accepted: 27 April 2018 / Published: 30 April 2018
PDF Full-text (1676 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
The enzymatic synthesis of nucleotides offers several advantages over traditional multistep chemical methods, such as stereoselectivity, regioselectivity, enantioselectivity, simple downstream processing, and the use of mild reaction conditions. However, in order to scale up these bioprocesses, several drawbacks, such as the low enzyme
[...] Read more.
The enzymatic synthesis of nucleotides offers several advantages over traditional multistep chemical methods, such as stereoselectivity, regioselectivity, enantioselectivity, simple downstream processing, and the use of mild reaction conditions. However, in order to scale up these bioprocesses, several drawbacks, such as the low enzyme stability and recycling, must be considered. Enzyme immobilization may overcome these cost-related problems by enhancing protein stability and facilitating the separation of products. In this regard, tetrameric hypoxanthine–guanine–xanthine phosphoribosyltransferase (HGXPRT) from Thermus thermophilus HB8 was covalently immobilized onto glutaraldehyde-activated MagReSyn®Amine magnetic iron oxide porous microparticles (MTtHGXPRT). In this context, two different strategies were followed: (a) an enzyme immobilization through its N-terminus residues at pH 8.5 (derivatives MTtHGXPRT1-3); and (b) a multipoint covalent immobilization through the surface lysine residues at pH 10 (derivatives MTtHGXPRT4-5). The immobilized derivatives of MTtHGXPRT3 (activity 1581 international units per gram of support, IU/g; retained activity 29%) and MTtHGXPRT5 (activity 1108 IU/g; retained activity 23%) displayed the best wet biocatalyst activity, and retained activity values in the enzymatic synthesis of inosine-5′-monophosphate (IMP). In addition, the dependence of the activities and stabilities of both derivatives on pH and temperature was tested, as well as their reusability potential. Taking these results into account, MTtHGXPRT3 was chosen as the best biocatalyst (negligible loss of activity at 60 °C during 24 h; reusable up to seven cycles). Finally, as proof of concept, the enzymatic production of dietary nucleotides from high concentrations of low soluble bases was achieved. Full article
(This article belongs to the Special Issue Immobilized Biocatalysts)
Figures

Graphical abstract

Open AccessArticle Rapid Immobilization of Cellulase onto Graphene Oxide with a Hydrophobic Spacer
Catalysts 2018, 8(5), 180; https://doi.org/10.3390/catal8050180
Received: 29 March 2018 / Revised: 18 April 2018 / Accepted: 25 April 2018 / Published: 28 April 2018
PDF Full-text (667 KB) | HTML Full-text | XML Full-text
Abstract
A rapid immobilization method for cellulase was developed. Functional graphene oxide was synthesized and grafted with hydrophobic spacer P-β-sulfuric acid ester ethyl sulfone aniline (SESA) though etherification and diazotization. The functionalized graphene oxide was characterized by Fourier-transform infrared spectroscopy and was used as
[...] Read more.
A rapid immobilization method for cellulase was developed. Functional graphene oxide was synthesized and grafted with hydrophobic spacer P-β-sulfuric acid ester ethyl sulfone aniline (SESA) though etherification and diazotization. The functionalized graphene oxide was characterized by Fourier-transform infrared spectroscopy and was used as the carrier for the immobilization of cellulase via covalent binding. The immobilization of cellulase was finished in a very short time (10 min) and very high immobilization yield and efficiency of above 90% were achieved after optimization. When compared with the free cellulase, thermal and operational stabilities of the immobilized cellulase were improved significantly. At 50 °C, the half-life of the immobilized cellulase (533 min) was six-fold higher than that of the free cellulase (89 min). Additionally, the affinity between immobilized cellulase (Km = 2.19 g·L−1) and substrate was more favorable than that of free cellulase (Km = 3.84 g·L−1), suggesting the immobilized cellulase has higher catalytic efficiency. The possible immobilization mechanism was proposed. The results strongly indicate that the immobilization is highly efficient and has great potential for the immobilization of other enzymes. Full article
(This article belongs to the Special Issue Immobilized Biocatalysts)
Figures

Graphical abstract

Open AccessArticle Heterogeneous Biocatalysts Prepared by Immuring Enzymatic Active Components inside Silica Xerogel and Nanocarbons-In-Silica Composites
Catalysts 2018, 8(5), 177; https://doi.org/10.3390/catal8050177
Received: 22 March 2018 / Revised: 16 April 2018 / Accepted: 20 April 2018 / Published: 26 April 2018
PDF Full-text (3333 KB) | HTML Full-text | XML Full-text
Abstract
Proprietary results on preparation and studies of whole-cell and lysates-based heterogeneous biocatalysts with different enzymatic activity were reviewed. A peculiar method was developed for preparing these biocatalysts by immuring (entrapping) enzymatic active components (EAC) inside silica (SiO2) xerogel and nanocarbons-in-silica composites.
[...] Read more.
Proprietary results on preparation and studies of whole-cell and lysates-based heterogeneous biocatalysts with different enzymatic activity were reviewed. A peculiar method was developed for preparing these biocatalysts by immuring (entrapping) enzymatic active components (EAC) inside silica (SiO2) xerogel and nanocarbons-in-silica composites. Properties of the multi-component composite biocatalysts such as enzymatic activity and operational stability were compared. The effect of the inclusion of nanocarbons such as nanotubes, nanofibers, and onion-like nanospheres with various texture, nanostructure and dispersion were thoroughly studied. With invertase-active biocatalysts, the direct correlation between an increase in the enzymatic activity of the nanocarbons-in-silica biocatalyst and efficiency of EAC adhesion on nanocarbons was observed. The steady-state invertase activity of the baker yeast lysates-based biocatalysts was determined to increase by a factor of 5–6 after inclusion of the multi-walled carbon nanotubes inside SiO2-xerogel. With lipase-active biocatalysts, the effect of the included nanocarbons on the biocatalytic properties depended significantly on the reaction type. In interesterification of oil-fat blends, the biocatalysts without any included nanocarbons demonstrated the maximal lipase activity. In esterification of fatty acids with aliphatic alcohols, the activity of the biocatalysts increased by a factor of 1.5–2 after inclusion of the aggregated multi-walled carbon nanotubes (CNTs) inside SiO2-xerogel. In the low-temperature synthesis of isopentyl esters of butyric (C4:0), capric (C10:0), and srearic (C18:0) fatty acids, the lipase-active composite CNTs-in-silica biocatalysts operated without loss of activity for more than thousand hours. Full article
(This article belongs to the Special Issue Immobilized Biocatalysts)
Figures

Figure 1

Open AccessArticle Immobilization of Planococcus sp. S5 Strain on the Loofah Sponge and Its Application in Naproxen Removal
Catalysts 2018, 8(5), 176; https://doi.org/10.3390/catal8050176
Received: 30 March 2018 / Revised: 22 April 2018 / Accepted: 23 April 2018 / Published: 26 April 2018
PDF Full-text (2202 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Planococcus sp. S5, a Gram-positive bacterium isolated from the activated sludge is known to degrade naproxen in the presence of an additional carbon source. Due to the possible toxicity of naproxen and intermediates of its degradation, the whole cells of S5 strain were
[...] Read more.
Planococcus sp. S5, a Gram-positive bacterium isolated from the activated sludge is known to degrade naproxen in the presence of an additional carbon source. Due to the possible toxicity of naproxen and intermediates of its degradation, the whole cells of S5 strain were immobilized onto loofah sponge. The immobilized cells degraded 6, 9, 12 or 15 mg/L of naproxen faster than the free cells. Planococcus sp. cells immobilized onto the loofah sponge were able to degrade naproxen efficiently for 55 days without significant damage and disintegration of the carrier. Analysis of the activity of enzymes involved in naproxen degradation showed that stabilization of S5 cells in exopolysaccharide (EPS) resulted in a significant increase of their activity. Changes in the structure of biofilm formed on the loofah sponge cubes during degradation of naproxen were observed. Developed biocatalyst system showed high resistance to naproxen and its intermediates and degraded higher concentrations of the drug in comparison to the free cells. Full article
(This article belongs to the Special Issue Immobilized Biocatalysts)
Figures

Figure 1

Open AccessArticle Maltose Production Using Starch from Cassava Bagasse Catalyzed by Cross-Linked β-Amylase Aggregates
Catalysts 2018, 8(4), 170; https://doi.org/10.3390/catal8040170
Received: 20 March 2018 / Revised: 17 April 2018 / Accepted: 19 April 2018 / Published: 21 April 2018
Cited by 1 | PDF Full-text (2524 KB) | HTML Full-text | XML Full-text
Abstract
Barley β-amylase was immobilized using different techniques. The highest global yield was obtained using the cross-linked enzyme aggregates (CLEA) technique, employing bovine serum albumin (BSA) or soy protein isolate (SPI) as feeder proteins to reduce diffusion problems. The CLEAs produced using BSA or
[...] Read more.
Barley β-amylase was immobilized using different techniques. The highest global yield was obtained using the cross-linked enzyme aggregates (CLEA) technique, employing bovine serum albumin (BSA) or soy protein isolate (SPI) as feeder proteins to reduce diffusion problems. The CLEAs produced using BSA or SPI showed 82.7 ± 5.8 and 53.3 ± 2.4% global yield, respectively, and a stabilization effect was observed upon immobilization at neutral pH value, e.g., after 12 h at 55 °C, the free β-amylase is fully inactivated, while CLEAs retained 25 and 15% of activity (using BSA and SPI, respectively). CLEA using SPI was selected because of its easier recovery, being chosen to convert the residual starch contained in cassava bagasse into maltose. This biocatalyst permitted to reach almost 70% of maltose conversion in 4 h using 30.0 g/L bagasse starch solution (Dextrose Equivalent of 15.88) and 1.2 U of biocatalyst per gram of starch at pH 7.0 and 40 °C. After 4 reuses (batches of 12 h) the CLEA using SPI maintained 25.50 ± 0.01% of conversion due to the difficulty of recovering. Full article
(This article belongs to the Special Issue Immobilized Biocatalysts)
Figures

Graphical abstract

Open AccessArticle Co-Immobilization of Ketoreductase and Glucose Dehydrogenase
Catalysts 2018, 8(4), 168; https://doi.org/10.3390/catal8040168
Received: 29 March 2018 / Revised: 12 April 2018 / Accepted: 18 April 2018 / Published: 20 April 2018
PDF Full-text (2750 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
A two-enzyme system composed of immobilized ketoreductase (Hansenula polymorpha) and glucose dehydrogenase (Bacillus megaterium) was developed for the asymmetric reduction of keto esters to optically active hydroxy esters via immobilization in polyvinyl alcohol (PVA) gel particles. The concentration of
[...] Read more.
A two-enzyme system composed of immobilized ketoreductase (Hansenula polymorpha) and glucose dehydrogenase (Bacillus megaterium) was developed for the asymmetric reduction of keto esters to optically active hydroxy esters via immobilization in polyvinyl alcohol (PVA) gel particles. The concentration of enzymes was optimized, and the final particles were used 18 times in a row in a batch mode to achieve minimal loss of activity and complete conversion of the model substrate, β-ketoester ethyl-2-methylacetoacetate. Excellent stability was also achieved using new storage conditions of PVA particles, with 80% of activity being retained after almost 10 months. Full article
(This article belongs to the Special Issue Immobilized Biocatalysts)
Figures

Figure 1

Open AccessArticle Asymmetric Ketone Reduction by Immobilized Rhodotorula mucilaginosa
Catalysts 2018, 8(4), 165; https://doi.org/10.3390/catal8040165
Received: 29 March 2018 / Revised: 16 April 2018 / Accepted: 17 April 2018 / Published: 19 April 2018
PDF Full-text (1968 KB) | HTML Full-text | XML Full-text
Abstract
In our previous study, Rhodotorula mucilaginosa (R. mucilaginosa) was selected via high throughput screening as a very active and selective whole-cell biocatalyst for the asymmetric reduction of ketones. In this study, the reduction of ketones to the desired chiral alcohols by
[...] Read more.
In our previous study, Rhodotorula mucilaginosa (R. mucilaginosa) was selected via high throughput screening as a very active and selective whole-cell biocatalyst for the asymmetric reduction of ketones. In this study, the reduction of ketones to the desired chiral alcohols by immobilized cells of this strain was investigated. Characterization with Fourier-transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM) showed that whole R. mucilaginosa cells were successfully immobilized on support matrices composed of agar, calcium alginate, PVA-alginate and chitosan. The immobilized cells were applied to the enantioselective reduction of fourteen different aromatic ketones. Good to excellent results were achieved with R. mucilaginosa cells immobilized on agar and calcium alginate. The immobilized cells on the selected support matrix composed of agar exhibited a significant increase in pH tolerance at pH 3.5–9 and demonstrated highly improved thermal stability compared to free cells. The cells immobilized on agar retained 90% activity after 60 days storage at 4 °C and retained almost 100% activity after 6 reuse cycles. In addition, the immobilization procedures are very simple and cause minimal pollution. These results suggest that the application of immobilized R. mucilaginosa can be practical on an industrial scale to produce chiral alcohols. Full article
(This article belongs to the Special Issue Immobilized Biocatalysts)
Figures

Figure 1a

Open AccessFeature PaperArticle Immobilization of Enterobacter aerogenes by a Trimeric Autotransporter Adhesin, AtaA, and Its Application to Biohydrogen Production
Catalysts 2018, 8(4), 159; https://doi.org/10.3390/catal8040159
Received: 30 March 2018 / Revised: 13 April 2018 / Accepted: 13 April 2018 / Published: 16 April 2018
PDF Full-text (3321 KB) | HTML Full-text | XML Full-text
Abstract
Biological hydrogen production by microbial cells has been extensively researched as an energy-efficient and environmentally-friendly process. In this study, we propose a fast, easy method for immobilizing Enterobacter aerogenes by expressing ataA, which encodes the adhesive protein of Acinetobacter sp. Tol 5.
[...] Read more.
Biological hydrogen production by microbial cells has been extensively researched as an energy-efficient and environmentally-friendly process. In this study, we propose a fast, easy method for immobilizing Enterobacter aerogenes by expressing ataA, which encodes the adhesive protein of Acinetobacter sp. Tol 5. AtaA protein on the E. aerogenes cells carrying the ataA gene was demonstrated by immunoblotting and flow cytometry. The AtaA-producing cells exhibited stronger adherence and auto-agglutination characteristics than wild-type cells, and were successfully immobilized (at approximately 2.5 mg/cm3) on polyurethane foam. Hydrogen production from the cell-immobilized polyurethane foams was monitored in repetitive batch reactions and flow reactor studies. The total hydrogen production in triple-repetitive batch reactions reached 0.6 mol/mol glucose, and the hydrogen production rate in the flow reactor was 42 mL·h−1·L−1. The AtaA production achieved simple and immediate immobilization of E. aerogenes on the foam, enabling repetitive and continuous hydrogen production. This report newly demonstrates the production of AtaA on the cell surfaces of bacterial genera other than Acinetobacter, and can simplify and accelerate the immobilization of whole-cell catalysts. Full article
(This article belongs to the Special Issue Immobilized Biocatalysts)
Figures

Graphical abstract

Open AccessArticle Preparation of Stable Cross-Linked Enzyme Aggregates (CLEAs) of a Ureibacillus thermosphaericus Esterase for Application in Malathion Removal from Wastewater
Catalysts 2018, 8(4), 154; https://doi.org/10.3390/catal8040154
Received: 26 March 2018 / Revised: 8 April 2018 / Accepted: 8 April 2018 / Published: 11 April 2018
Cited by 1 | PDF Full-text (16248 KB) | HTML Full-text | XML Full-text
Abstract
In this study, the active and stable cross-linked enzyme aggregates (CLEAs) of the thermostable esterase estUT1 of the bacterium Ureibacillus thermosphaericus were prepared for application in malathion removal from municipal wastewater. Co-expression of esterase with an E. coli chaperone team (KJE, ClpB, and
[...] Read more.
In this study, the active and stable cross-linked enzyme aggregates (CLEAs) of the thermostable esterase estUT1 of the bacterium Ureibacillus thermosphaericus were prepared for application in malathion removal from municipal wastewater. Co-expression of esterase with an E. coli chaperone team (KJE, ClpB, and ELS) increased the activity of the soluble enzyme fraction up to 200.7 ± 15.5 U mg−1. Response surface methodology (RSM) was used to optimize the preparation of the CLEA-estUT1 biocatalyst to maximize its activity and minimize enzyme loss. CLEA-estUT1 with the highest activity of 29.4 ± 0.5 U mg−1 (90.6 ± 2.7% of the recovered activity) was prepared with 65.1% (w/v) ammonium sulfate, 120.6 mM glutaraldehyde, and 0.2 mM bovine serum albumin at 5.1 h of cross-linking. The biocatalyst has maximal activity at 80 °С and pH 8.0. Analysis of the properties of CLEA-estUT1 and free enzyme at 50–80 °C and pH 5.0–10.0 showed higher stability of the biocatalyst. CLEA-estUT1 showed marked tolerance against a number of chemicals and high operational stability and activity in the reaction of malathion hydrolysis in wastewater (up to 99.5 ± 1.4%). After 25 cycles of malathion hydrolysis at 37 °С, it retained 55.2 ± 1.1% of the initial activity. The high stability and reusability of CLEA-estUT1 make it applicable for the degradation of insecticides. Full article
(This article belongs to the Special Issue Immobilized Biocatalysts)
Figures

Figure 1

Open AccessArticle Immobilization/Stabilization of Ficin Extract on Glutaraldehyde-Activated Agarose Beads. Variables That Control the Final Stability and Activity in Protein Hydrolyses
Catalysts 2018, 8(4), 149; https://doi.org/10.3390/catal8040149
Received: 12 March 2018 / Revised: 26 March 2018 / Accepted: 2 April 2018 / Published: 6 April 2018
PDF Full-text (17097 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Ficin extract has been immobilized on different 4% aminated-agarose beads. Using just ion exchange, immobilization yield was poor and expressed activity did not surpass 10% of the offered enzyme, with no significant effects on enzyme stability. The treatment with glutaraldehyde of this ionically
[...] Read more.
Ficin extract has been immobilized on different 4% aminated-agarose beads. Using just ion exchange, immobilization yield was poor and expressed activity did not surpass 10% of the offered enzyme, with no significant effects on enzyme stability. The treatment with glutaraldehyde of this ionically exchanged enzyme produced an almost full enzyme inactivation. Using aminated supports activated with glutaraldehyde, immobilization was optimal at pH 7 (at pH 5 immobilization yield was 80%, while at pH 9, the immobilized enzyme became inactivated). At pH 7, full immobilization was accomplished maintaining 40% activity versus a small synthetic substrate and 30% versus casein. Ficin stabilization upon immobilization could be observed but it depended on the inactivation pH and the substrate employed, suggesting the complexity of the mechanism of inactivation of the immobilized enzyme. The maximum enzyme loading on the support was determined to be around 70 mg/g. The loading has no significant effect on the enzyme stability or enzyme activity using the synthetic substrate but it had a significant effect on the activity using casein; the biocatalysts activity greatly decreased using more than 30 mg/g, suggesting that the near presence of other immobilized enzyme molecules may generate some steric hindrances for the casein hydrolysis. Full article
(This article belongs to the Special Issue Immobilized Biocatalysts)
Figures

Graphical abstract

Open AccessArticle X-Shaped ZIF-8 for Immobilization Rhizomucor miehei Lipase via Encapsulation and Its Application toward Biodiesel Production
Catalysts 2018, 8(3), 96; https://doi.org/10.3390/catal8030096
Received: 25 January 2018 / Revised: 21 February 2018 / Accepted: 26 February 2018 / Published: 28 February 2018
Cited by 1 | PDF Full-text (7247 KB) | HTML Full-text | XML Full-text
Abstract
This study presents a one-step encapsulation method for synthesizing X-shaped zeolitic imidazolate frameworks (ZIF-8) and immobilizing Rhizomucor miehei lipase (RML). We proved that the morphological structure of ZIF-8 had changed after immobilization with enhanced characterization using a field-emission scanning electron microscope, an energy-dispersive
[...] Read more.
This study presents a one-step encapsulation method for synthesizing X-shaped zeolitic imidazolate frameworks (ZIF-8) and immobilizing Rhizomucor miehei lipase (RML). We proved that the morphological structure of ZIF-8 had changed after immobilization with enhanced characterization using a field-emission scanning electron microscope, an energy-dispersive spectrometer, a transmission electron microscope, a Fourier transform infrared spectrometer, and powder X-ray diffraction. The surface area and pore size of the carrier were investigated before and after immobilization using Brunauer–Emmett–Teller and Barrett–Joyner–Halenda methods, respectively. RML@ZIF-8 exhibited high recovery activity of up to 2632%, representing a 26-fold increase in its free lipase. Encapsulated RML was used for biodiesel production from soybean oil in an isooctane system with a conversion yield of 95.6% under optimum conditions. The resulting reusability of the immobilized enzyme indicated no substantial decline in the conversion yield, which remained at 84.7% of the initial activity after 10 cycles. The stability and high performance of the immobilized enzyme are attributed to the harmony between RML and ZIF-8 based on the easy synthesis of ZIF-8 and the short time required to immobilize RML. Full article
(This article belongs to the Special Issue Immobilized Biocatalysts)
Figures

Figure 1

Open AccessArticle Immobilization Effects on the Catalytic Properties of Two Fusarium Verticillioides Lipases: Stability, Hydrolysis, Transesterification and Enantioselectivity Improvement
Catalysts 2018, 8(2), 84; https://doi.org/10.3390/catal8020084
Received: 15 December 2017 / Revised: 30 January 2018 / Accepted: 2 February 2018 / Published: 16 February 2018
PDF Full-text (3305 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Fusarium verticillioides lipases were purified in a “cascade” method using octadecyl Sepabeads and octyl Sepharose resins, which led to the isolation of two proteins with lipolytic activities. Lip 1 was purified after octyl Sepharose adsorption presenting 30.3 kDa and, Lip 2 presented 68.0
[...] Read more.
Fusarium verticillioides lipases were purified in a “cascade” method using octadecyl Sepabeads and octyl Sepharose resins, which led to the isolation of two proteins with lipolytic activities. Lip 1 was purified after octyl Sepharose adsorption presenting 30.3 kDa and, Lip 2 presented 68.0 kDa after octadecyl adsorption. These immobilization processes resulted in an increase of 3-fold in activity of each immobilized enzyme. These enzymes presented optima of pH of 5.0 and 6.0, respectively and temperature at 40 °C. They were thermostable at 40 °C and both remained more than 50% of its activity at the pH range of 5.0 to 7.0, with 180 min of incubation. The sardine oil hydrolysis showed higher EPA/DHA ratio. Concerning the ethanolysis reaction, Lip 2 showed higher conversion (5.5%) and both lipases showed activity in the release of the S enantiomers from 2-O-butyryl-2-phenylacetic acid (mandelic butyrate acid) and HPBE hydrolysis. Lip 2 also demonstrated capacity of transesterification. These applications made these enzymes attractive for industrial application. Full article
(This article belongs to the Special Issue Immobilized Biocatalysts)
Figures

Figure 1

Open AccessArticle Genetically Fused T4L Acts as a Shield in Covalent Enzyme Immobilisation Enhancing the Rescued Activity
Catalysts 2018, 8(1), 40; https://doi.org/10.3390/catal8010040
Received: 3 January 2018 / Revised: 15 January 2018 / Accepted: 16 January 2018 / Published: 20 January 2018
PDF Full-text (1006 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Enzyme immobilisation is a common strategy to increase enzymes resistance and reusability in a variety of excellent ‘green’ applications. However, the interaction with the solid support often leads to diminished specific activity, especially when non-specific covalent binding to the carrier takes place which
[...] Read more.
Enzyme immobilisation is a common strategy to increase enzymes resistance and reusability in a variety of excellent ‘green’ applications. However, the interaction with the solid support often leads to diminished specific activity, especially when non-specific covalent binding to the carrier takes place which affects the delicate architecture of the enzyme. Here we developed a broadly applicable strategy where the T4-lysozyme (T4L) is genetically fused at the N-terminus of different enzymes and used as inert protein spacer which directly attaches to the carrier preventing shape distortion of the catalyst. Halomonas elongata aminotransferase (HEWT), Bacillus subtilis engineered esterase (BS2m), and horse liver alcohol dehydrogenase (HLADH) were used as model enzymes to elucidate the benefits of the spacer. While HEWT and HLADH activity and expression were diminished by the fused T4L, both enzymes retained almost quantitative activity after immobilisation. In the case of BS2m, the protective effect of the T4L effectively was important and led to up to 10-fold improvement in the rescued activity. Full article
(This article belongs to the Special Issue Immobilized Biocatalysts)
Figures

Graphical abstract

Open AccessCommunication Co-Detection of Dopamine and Glucose with High Temporal Resolution
Catalysts 2018, 8(1), 34; https://doi.org/10.3390/catal8010034
Received: 6 December 2017 / Revised: 11 January 2018 / Accepted: 15 January 2018 / Published: 19 January 2018
PDF Full-text (1804 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Neuronal activity and brain glucose metabolism are tightly coupled, where triggered neurotransmission leads to a higher demand for glucose. To better understand the regulation of neuronal activity and its relation to high-speed metabolism, development of analytical tools that can temporally resolve the transients
[...] Read more.
Neuronal activity and brain glucose metabolism are tightly coupled, where triggered neurotransmission leads to a higher demand for glucose. To better understand the regulation of neuronal activity and its relation to high-speed metabolism, development of analytical tools that can temporally resolve the transients of vesicular neurotransmitter release and fluctuations of metabolites such as glucose in the local vicinity of the activated neurons is needed. Here we present an amperometric biosensor design for rapid co-detection of glucose and the neurotransmitter dopamine. The sensor is based on the immobilization of an ultra-thin layer of glucose oxidase on to a gold-nanoparticle-covered carbon fiber microelectrode. Our electrode, by altering the potential applied at the sensor surface, allows for the high-speed recording of both glucose and dopamine. We demonstrate that, even though glucose is electrochemically detected indirectly through the enzymatic product and the electroactive dopamine is sensed directly, when exposing the sensor surface to a mixture of the two analytes, fluctuations in glucose and dopamine concentrations can be visualized with similar speed and at a millisecond time scale. Hence, by minimizing the enzyme coating thickness at the sensor surface, dual detection of glucose and dopamine can be realized at the same sensor surface and at time scales necessary for monitoring fast metabolic alterations during neurotransmission. Full article
(This article belongs to the Special Issue Immobilized Biocatalysts)
Figures

Graphical abstract

Open AccessArticle “Deceived” Concentrated Immobilized Cells as Biocatalyst for Intensive Bacterial Cellulose Production from Various Sources
Catalysts 2018, 8(1), 33; https://doi.org/10.3390/catal8010033
Received: 21 December 2017 / Revised: 9 January 2018 / Accepted: 15 January 2018 / Published: 18 January 2018
PDF Full-text (4240 KB) | HTML Full-text | XML Full-text
Abstract
A new biocatalyst in the form of Komagataeibacter xylinum B-12429 cells immobilized in poly(vinyl alcohol) cryogel for production of bacterial cellulose was demonstrated. Normally, the increased bacteria concentration causes an enlarged bacterial cellulose synthesis while cells push the polysaccharide out to pack themselves
[...] Read more.
A new biocatalyst in the form of Komagataeibacter xylinum B-12429 cells immobilized in poly(vinyl alcohol) cryogel for production of bacterial cellulose was demonstrated. Normally, the increased bacteria concentration causes an enlarged bacterial cellulose synthesis while cells push the polysaccharide out to pack themselves into this polymer and go into a stasis. Immobilization of cells into the poly(vinyl alcohol) cryogel allowed “deceiving” them: bacteria producing cellulose pushed it out, which further passed through the pores of cryogel matrix and was accumulated in the medium while not covering the cells; hence, the latter were deprived of a possible transition to inactivity and worked on the synthesis of bacterial cellulose even more actively. The repeated use of immobilized cells retaining 100% of their metabolic activity for at least 10 working cycles (60 days) was performed. The immobilized cells produce bacterial cellulose with crystallinity and porosity similar to polysaccharide of free cells, but having improved stiffness and tensile strength. Various media containing sugars and glycerol, based on hydrolysates of renewable biomass sources (aspen, Jerusalem artichoke, rice straw, microalgae) were successfully applied for bacterial cellulose production by immobilized cells, and the level of polysaccharide accumulation was 1.3–1.8-times greater than suspended cells could produce. Full article
(This article belongs to the Special Issue Immobilized Biocatalysts)
Figures

Figure 1

Open AccessArticle Immobilization of Cellulase on a Functional Inorganic–Organic Hybrid Support: Stability and Kinetic Study
Catalysts 2017, 7(12), 374; https://doi.org/10.3390/catal7120374
Received: 7 November 2017 / Revised: 28 November 2017 / Accepted: 29 November 2017 / Published: 1 December 2017
Cited by 2 | PDF Full-text (1637 KB) | HTML Full-text | XML Full-text
Abstract
Cellulase from Aspergillus niger was immobilized on a synthesized TiO2–lignin hybrid support. The enzyme was effectively deposited on the inorganic–organic hybrid matrix, mainly via physical interactions. The optimal initial immobilization parameters, selected for the highest relative activity, were pH 5.0, 6
[...] Read more.
Cellulase from Aspergillus niger was immobilized on a synthesized TiO2–lignin hybrid support. The enzyme was effectively deposited on the inorganic–organic hybrid matrix, mainly via physical interactions. The optimal initial immobilization parameters, selected for the highest relative activity, were pH 5.0, 6 h process duration, and an enzyme solution concentration of 5 mg/mL. Moreover, the effects of pH, temperature, and number of consecutive catalytic cycles and the storage stability of free and immobilized cellulase were evaluated and compared. Thermal and chemical stability were significantly improved, while after 3 h at a temperature of 50 °C and pH 6.0, the immobilized cellulase retained over 80% of its initial activity. In addition, the half-life of the immobilized cellulase (307 min) was five times that of the free enzyme (63 min). After ten repeated catalytic cycles, the immobilized biocatalyst retained over 90% of its initial catalytic properties. This study presents a protocol for the production of highly stable and reusable biocatalytic systems for practical application in the hydrolysis of cellulose. Full article
(This article belongs to the Special Issue Immobilized Biocatalysts)
Figures

Figure 1

Open AccessArticle Approaching Immobilization of Enzymes onto Open Porous Basotect®
Catalysts 2017, 7(12), 359; https://doi.org/10.3390/catal7120359
Received: 17 October 2017 / Revised: 14 November 2017 / Accepted: 16 November 2017 / Published: 27 November 2017
PDF Full-text (2608 KB) | HTML Full-text | XML Full-text
Abstract
For the first time, commercial macroporous melamine formaldehyde foam Basotect® (BT) was used as a basic carrier material for both adsorptive and covalent enzyme immobilization. In order to access inherent amino groups, the Basotect® surface was pretreated with hydrochloric acid. The
[...] Read more.
For the first time, commercial macroporous melamine formaldehyde foam Basotect® (BT) was used as a basic carrier material for both adsorptive and covalent enzyme immobilization. In order to access inherent amino groups, the Basotect® surface was pretreated with hydrochloric acid. The resulting material revealed 6 nmol of superficial amino groups per milligram Basotect®. Different optimized strategies for tethering the laccase from Trametes versicolor and the lipase from Thermomyces lanuginosus onto the pre-treated Basotect® surface were studied. Particularly, for covalent immobilization, two different strategies were pursued: lipase was tethered via a cross-linking method using 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide, and laccase was bound after functionalizing Basotect® with hydrophilic copolymer poly(ethylene-alt-maleic anhydride) (PEMA). Prior to laccase immobilization, the PEMA coating of Basotect® was verified by ATR-FTIR analysis. Subsequent quantification of available high-reactive PEMA anhydride moieties revealed an amount of 1028 ± 73 nmol per mg Basotect®. The surface-bound enzyme amounts were quantified as 4.1–5.8 μg per mg Basotect®. A theoretical surface-covered enzyme mass for the ideal case that an enzyme monolayer was immobilized onto the Basotect® surface was calculated and compared to the amount of adsorptive and covalently bound enzymes before and after treatment with SDS. Furthermore, the enzyme activities were determined for the different immobilization approaches, and the stability during storage over time and against sodium dodecyl sulfate treatment was monitored. Additionally, PEMA-BT-bound laccase was tested for the elimination of anthropogenic micropollutant bisphenol A from contaminated water in a cost-effective and environmentally-friendly way and resulted in a degradation rate higher than 80%. Full article
(This article belongs to the Special Issue Immobilized Biocatalysts)
Figures

Figure 1

Open AccessArticle Polyelectrolyte Complex Beads by Novel Two-Step Process for Improved Performance of Viable Whole-Cell Baeyer-Villiger Monoxygenase by Immobilization
Catalysts 2017, 7(11), 353; https://doi.org/10.3390/catal7110353
Received: 18 October 2017 / Revised: 10 November 2017 / Accepted: 13 November 2017 / Published: 21 November 2017
PDF Full-text (4337 KB) | HTML Full-text | XML Full-text
Abstract
A novel immobilization matrix for the entrapment of viable whole-cell Baeyer–Villiger monooxygenase was developed. Viable recombinant Escherichia coli cells overexpressing cyclohexanone monooxygenase were entrapped in polyelectrolyte complex beads prepared by a two-step reaction of oppositely-charged polymers including highly defined cellulose sulphate. Immobilized cells
[...] Read more.
A novel immobilization matrix for the entrapment of viable whole-cell Baeyer–Villiger monooxygenase was developed. Viable recombinant Escherichia coli cells overexpressing cyclohexanone monooxygenase were entrapped in polyelectrolyte complex beads prepared by a two-step reaction of oppositely-charged polymers including highly defined cellulose sulphate. Immobilized cells exhibited higher operational stability than free cells during 10 repeated cycles of Baeyer–Villiger biooxidations of rac-bicyclo[3.2.0]hept-2-en-6-one to the corresponding lactones (1R,5S)-3-oxabicyclo-[3.3.0]oct-6-en-3-one and (1S,5R)-2-oxabicyclo-[3.3.0]oct-6-en-3-one. The morphology of polyelectrolyte complex beads was characterised by environmental scanning electron microscopy; the spatial distribution of polymers in the beads and cell viability were examined using confocal laser scanning microscopy, and the texture was characterised by the mechanical resistance measurements. Full article
(This article belongs to the Special Issue Immobilized Biocatalysts)
Figures

Figure 1

Open AccessCommunication In-Situ Self-Assembly of Zinc/Adenine Hybrid Nanomaterials for Enzyme Immobilization
Catalysts 2017, 7(11), 327; https://doi.org/10.3390/catal7110327
Received: 16 October 2017 / Revised: 27 October 2017 / Accepted: 27 October 2017 / Published: 3 November 2017
Cited by 1 | PDF Full-text (3181 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
In this study, a one-step and facile immobilization of enzymes by self-assembly of zinc ions and adenine in aqueous solution with mild conditions was reported. Enzymes, such as glucose oxidase (GOx) and horseradish peroxidase (HRP), could be efficiently encapsulated in Zn/adenine coordination polymers
[...] Read more.
In this study, a one-step and facile immobilization of enzymes by self-assembly of zinc ions and adenine in aqueous solution with mild conditions was reported. Enzymes, such as glucose oxidase (GOx) and horseradish peroxidase (HRP), could be efficiently encapsulated in Zn/adenine coordination polymers (CPs) with high loading capacity over 90%. When the enzyme was immobilized by CPs, it displayed high catalytic efficiency, high selectivity and enhanced stability due to the protecting effect of the rigid framework. As a result, the relative activity of Zn/adenine nano-CP-immobilized GOx increased by 1.5-fold at pH 3 and 4-fold at 70 to 90 °C, compared to free GOx. The immobilized GOx had excellent reusability (more than 90% relative activity after being reused eight times). Furthermore, the use of this system as a glucose biosensor was also demonstrated by co-immobilization of two enzymes, detecting glucose down to 1.84 µM with excellent selectivity. The above work indicated that in-situ self-assembly of Zn/adenine CPs could be a simple and efficient method for biocatalyst immobilization. Full article
(This article belongs to the Special Issue Immobilized Biocatalysts)
Figures

Graphical abstract

Review

Jump to: Research

Open AccessReview Industrial Applications of Enzymes: Recent Advances, Techniques, and Outlooks
Catalysts 2018, 8(6), 238; https://doi.org/10.3390/catal8060238
Received: 5 May 2018 / Revised: 25 May 2018 / Accepted: 30 May 2018 / Published: 5 June 2018
PDF Full-text (2705 KB) | HTML Full-text | XML Full-text
Abstract
Enzymes as industrial biocatalysts offer numerous advantages over traditional chemical processes with respect to sustainability and process efficiency. Enzyme catalysis has been scaled up for commercial processes in the pharmaceutical, food and beverage industries, although further enhancements in stability and biocatalyst functionality are
[...] Read more.
Enzymes as industrial biocatalysts offer numerous advantages over traditional chemical processes with respect to sustainability and process efficiency. Enzyme catalysis has been scaled up for commercial processes in the pharmaceutical, food and beverage industries, although further enhancements in stability and biocatalyst functionality are required for optimal biocatalytic processes in the energy sector for biofuel production and in natural gas conversion. The technical barriers associated with the implementation of immobilized enzymes suggest that a multidisciplinary approach is necessary for the development of immobilized biocatalysts applicable in such industrial-scale processes. Specifically, the overlap of technical expertise in enzyme immobilization, protein and process engineering will define the next generation of immobilized biocatalysts and the successful scale-up of their induced processes. This review discusses how biocatalysis has been successfully deployed, how enzyme immobilization can improve industrial processes, as well as focuses on the analysis tools critical for the multi-scale implementation of enzyme immobilization for increased product yield at maximum market profitability and minimum logistical burden on the environment and user. Full article
(This article belongs to the Special Issue Immobilized Biocatalysts)
Figures

Figure 1

Open AccessFeature PaperReview Controlling Redox Enzyme Orientation at Planar Electrodes
Catalysts 2018, 8(5), 192; https://doi.org/10.3390/catal8050192
Received: 13 April 2018 / Revised: 27 April 2018 / Accepted: 28 April 2018 / Published: 4 May 2018
PDF Full-text (6570 KB) | HTML Full-text | XML Full-text
Abstract
Redox enzymes, which catalyze reactions involving electron transfers in living organisms, are very promising components of biotechnological devices, and can be envisioned for sensing applications as well as for energy conversion. In this context, one of the most significant challenges is to achieve
[...] Read more.
Redox enzymes, which catalyze reactions involving electron transfers in living organisms, are very promising components of biotechnological devices, and can be envisioned for sensing applications as well as for energy conversion. In this context, one of the most significant challenges is to achieve efficient direct electron transfer by tunneling between enzymes and conductive surfaces. Based on various examples of bioelectrochemical studies described in the recent literature, this review discusses the issue of enzyme immobilization at planar electrode interfaces. The fundamental importance of controlling enzyme orientation, how to obtain such orientation, and how it can be verified experimentally or by modeling are the three main directions explored. Since redox enzymes are sizable proteins with anisotropic properties, achieving their functional immobilization requires a specific and controlled orientation on the electrode surface. All the factors influenced by this orientation are described, ranging from electronic conductivity to efficiency of substrate supply. The specificities of the enzymatic molecule, surface properties, and dipole moment, which in turn influence the orientation, are introduced. Various ways of ensuring functional immobilization through tuning of both the enzyme and the electrode surface are then described. Finally, the review deals with analytical techniques that have enabled characterization and quantification of successful achievement of the desired orientation. The rich contributions of electrochemistry, spectroscopy (especially infrared spectroscopy), modeling, and microscopy are featured, along with their limitations. Full article
(This article belongs to the Special Issue Immobilized Biocatalysts)
Figures

Figure 1

Open AccessReview Techniques for Preparation of Cross-Linked Enzyme Aggregates and Their Applications in Bioconversions
Catalysts 2018, 8(5), 174; https://doi.org/10.3390/catal8050174
Received: 27 March 2018 / Revised: 19 April 2018 / Accepted: 20 April 2018 / Published: 24 April 2018
PDF Full-text (1252 KB) | HTML Full-text | XML Full-text
Abstract
Enzymes are biocatalysts. They are useful in environmentally friendly production processes and have high potential for industrial applications. However, because of problems with operational stability, cost, and catalytic efficiency, many enzymatic processes have limited applications. The use of cross-linked enzyme aggregates (CLEAs) has
[...] Read more.
Enzymes are biocatalysts. They are useful in environmentally friendly production processes and have high potential for industrial applications. However, because of problems with operational stability, cost, and catalytic efficiency, many enzymatic processes have limited applications. The use of cross-linked enzyme aggregates (CLEAs) has been introduced as an effective carrier-free immobilization method. This immobilization method is attractive because it is simple and robust, and unpurified enzymes can be used. Coimmobilization of different enzymes can be achieved. CLEAs generally show high catalytic activities, good storage and operational stabilities, and good reusability. In this review, we summarize techniques for the preparation of CLEAs for use as biocatalysts. Some important applications of these techniques in chemical synthesis and environmental applications are also included. CLEAs provide feasible and efficient techniques for improving the properties of immobilized enzymes for use in industrial applications. Full article
(This article belongs to the Special Issue Immobilized Biocatalysts)
Figures

Figure 1

Open AccessReview Applications of Immobilized Bio-Catalyst in Metal-Organic Frameworks
Catalysts 2018, 8(4), 166; https://doi.org/10.3390/catal8040166
Received: 9 April 2018 / Revised: 18 April 2018 / Accepted: 18 April 2018 / Published: 20 April 2018
PDF Full-text (1767 KB) | HTML Full-text | XML Full-text
Abstract
Immobilization of bio-catalysts in solid porous materials has attracted much attention in the last few decades due to its vast application potential in ex vivo catalysis. Despite the high efficiency and selectivity of enzymatic catalytic processes, enzymes may suffer from denaturation under industrial
[...] Read more.
Immobilization of bio-catalysts in solid porous materials has attracted much attention in the last few decades due to its vast application potential in ex vivo catalysis. Despite the high efficiency and selectivity of enzymatic catalytic processes, enzymes may suffer from denaturation under industrial production conditions, which, in turn, diminish their catalytic performances and long-term recyclability. Metal-organic frameworks (MOFs), as a growing type of hybrid materials, have been identified as promising platforms for enzyme immobilization owing to their enormous structural and functional tunability, and extraordinary porosity. This review mainly focuses on the applications of enzyme@MOFs hybrid materials in catalysis, sensing, and detection. The improvements of catalytic activity and robustness of encapsulated enzymes over the free counterpart are discussed in detail. Full article
(This article belongs to the Special Issue Immobilized Biocatalysts)
Figures

Figure 1

Open AccessReview The Role of Yeast-Surface-Display Techniques in Creating Biocatalysts for Consolidated BioProcessing
Catalysts 2018, 8(3), 94; https://doi.org/10.3390/catal8030094
Received: 31 January 2018 / Revised: 19 February 2018 / Accepted: 21 February 2018 / Published: 25 February 2018
Cited by 1 | PDF Full-text (4326 KB) | HTML Full-text | XML Full-text
Abstract
Climate change is directly linked to the rapid depletion of our non-renewable fossil resources and has posed concerns on sustainability. Thus, imploring the need for us to shift from our fossil based economy to a sustainable bioeconomy centered on biomass utilization. The efficient
[...] Read more.
Climate change is directly linked to the rapid depletion of our non-renewable fossil resources and has posed concerns on sustainability. Thus, imploring the need for us to shift from our fossil based economy to a sustainable bioeconomy centered on biomass utilization. The efficient bioconversion of lignocellulosic biomass (an ideal feedstock) to a platform chemical, such as bioethanol, can be achieved via the consolidated bioprocessing technology, termed yeast surface engineering, to produce yeasts that are capable of this feat. This approach has various strategies that involve the display of enzymes on the surface of yeast to degrade the lignocellulosic biomass, then metabolically convert the degraded sugars directly into ethanol, thus elevating the status of yeast from an immobilization material to a whole-cell biocatalyst. The performance of the engineered strains developed from these strategies are presented, visualized, and compared in this article to highlight the role of this technology in moving forward to our quest against climate change. Furthermore, the qualitative assessment synthesized in this work can serve as a reference material on addressing the areas of improvement of the field and on assessing the capability and potential of the different yeast surface display strategies on the efficient degradation, utilization, and ethanol production from lignocellulosic biomass. Full article
(This article belongs to the Special Issue Immobilized Biocatalysts)
Figures

Figure 1

Open AccessReview A General Overview of Support Materials for Enzyme Immobilization: Characteristics, Properties, Practical Utility
Catalysts 2018, 8(2), 92; https://doi.org/10.3390/catal8020092
Received: 19 January 2018 / Revised: 12 February 2018 / Accepted: 21 February 2018 / Published: 24 February 2018
Cited by 8 | PDF Full-text (1154 KB) | HTML Full-text | XML Full-text
Abstract
In recent years, enzyme immobilization has been presented as a powerful tool for the improvement of enzyme properties such as stability and reusability. However, the type of support material used plays a crucial role in the immobilization process due to the strong effect
[...] Read more.
In recent years, enzyme immobilization has been presented as a powerful tool for the improvement of enzyme properties such as stability and reusability. However, the type of support material used plays a crucial role in the immobilization process due to the strong effect of these materials on the properties of the produced catalytic system. A large variety of inorganic and organic as well as hybrid and composite materials may be used as stable and efficient supports for biocatalysts. This review provides a general overview of the characteristics and properties of the materials applied for enzyme immobilization. For the purposes of this literature study, support materials are divided into two main groups, called Classic and New materials. The review will be useful in selection of appropriate support materials with tailored properties for the production of highly effective biocatalytic systems for use in various processes. Full article
(This article belongs to the Special Issue Immobilized Biocatalysts)
Figures

Figure 1

Back to Top