Special Issue "Biocatalysts and Their Environmental Applications"

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

Deadline for manuscript submissions: 31 May 2021.

Special Issue Editors

Prof. Dr. Baiyu Zhang
Website
Guest Editor
Northern Region Persistent Organic Pollution Control (NRPOP) Laboratory, Memorial University of Newfoundland, St John's, Canada
Interests: magnetic nano-biocatalysts; bioremediation
Dr. Bo Liu

Guest Editor
Department of Civil Engineering, Memorial University, St. John's, Canada
Interests: biological photocatalyst; microbial fuel cell; wastewater treatment

Special Issue Information

Dear Colleagues,

Biocatalysts, including a special species of microorganisms, and their enzymes have been widely accepted in many industrial processes, because they are less-toxic, environment friendly, and energy-conserving alternatives compared with chemical catalysts. Whole-cell biocatalysts have advantages (e.g., the elimination of the need for protein purification) and disadvantages (e.g., the reduced reaction rates) over purified enzymes.

The reaction rates in whole-cell biocatalysts can be achieved through many strategies, such as increasing the permeability of the cell membrane by chemical reactions; increasing the concentration of the enzyme within the cell by enzyme overexpression in a bacterial host; and stabilizing and improving the biocatalyst function by flocculation, surface immobilization, and encapsulation. Up unil now, whole-cell biocatalysts have been applied to environmental fields for enhancing transformation and degradation processes. Meanwhile, the growth synthetic biology and protein engineering greatly facilitates the development of novel biocatalysts specifically relevant to the production of fine chemicals for improving bulk enzymes for industry and the products involved in waste reduction and detoxification. Magnetic nano-biocatalysts are also a rapidly growing field for the development of sustainable and green processes.

This Special Issue will focus on different methodologies for biocatalyst development/improvement, and a large range of reactions employed in environmental remediation processes catalyzed by whole-cells and isolated enzymes. Persistent, toxic/carcinogenic, and/or bio-accumulative contaminants in multiple (air/liquid/solid) phases will be tackled. It aims to compile a set of manuscripts that cover the recent progress and trends in biocatalysts, and their environmental applications.

Dr. Dr. Baiyu Zhang
Dr. Bo Liu
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All 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 2000 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

  • whole cell biocatalysts
  • enzymes
  • magnetic nano-biocatalysts
  • environmental applications
  • contaminant transformation and degradation

Published Papers (4 papers)

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Research

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Open AccessArticle
Enhanced Hydrocarbons Biodegradation at Deep-Sea Hydrostatic Pressure with Microbial Electrochemical Snorkels
Catalysts 2021, 11(2), 263; https://doi.org/10.3390/catal11020263 - 16 Feb 2021
Abstract
In anaerobic sediments, microbial degradation of petroleum hydrocarbons is limited by the rapid depletion of electron acceptors (e.g., ferric oxide, sulfate) and accumulation of toxic metabolites (e.g., sulfide, following sulfate reduction). Deep-sea sediments are increasingly impacted by oil contamination, and the elevated hydrostatic [...] Read more.
In anaerobic sediments, microbial degradation of petroleum hydrocarbons is limited by the rapid depletion of electron acceptors (e.g., ferric oxide, sulfate) and accumulation of toxic metabolites (e.g., sulfide, following sulfate reduction). Deep-sea sediments are increasingly impacted by oil contamination, and the elevated hydrostatic pressure (HP) they are subjected to represents an additional limitation for microbial metabolism. While the use of electrodes to support electrobioremediation in oil-contaminated sediments has been described, there is no evidence on their applicability for deep-sea sediments. Here, we tested a passive bioelectrochemical system named ”oil-spill snorkel” with two crude oils carrying different alkane contents (4 vs. 15%), at increased or ambient HP (10 vs. 0.1 MPa). Snorkels enhanced alkanes biodegradation at both 10 and 0.1 MPa within only seven weeks, as compared to nonconductive glass controls. Microprofiles in anaerobic, contaminated sediments indicated that snorkels kept sulfide concentration to low titers. Bulk-sediment analysis confirmed that sulfide oxidation by snorkels largely regenerated sulfate. Hence, the sole application of snorkels could eliminate a toxicity factor and replenish a spent electron acceptor at increased HP. Both aspects are crucial for petroleum decontamination of the deep sea, a remote environment featured by low metabolic activity. Full article
(This article belongs to the Special Issue Biocatalysts and Their Environmental Applications)
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Open AccessArticle
Facile One-Pot Immobilization of a Novel Thermostable Carboxylesterase from Geobacillus uzenensis for Continuous Pesticide Degradation in a Packed-Bed Column Reactor
Catalysts 2020, 10(5), 518; https://doi.org/10.3390/catal10050518 - 07 May 2020
Cited by 1
Abstract
The novel carboxylesterase gene (est741) was cloned from Geobacillus uzenensis. The optimal pH and temperature of Est741 were 8.0 and 50 °C. Through site-directed mutation, the optimum temperature of the mutant M160K(EstM160K) was increased from 50 [...] Read more.
The novel carboxylesterase gene (est741) was cloned from Geobacillus uzenensis. The optimal pH and temperature of Est741 were 8.0 and 50 °C. Through site-directed mutation, the optimum temperature of the mutant M160K(EstM160K) was increased from 50 to 60 °C, and showed enhanced T1/2 of 2.5 h at 70 °C in comparison to the wild type (1.3 h). EstM160K was successfully expressed Pichia pastoris and EstM160K fermentation broth was directly immobilized on epoxy-functionalized supports via a one-pot strategy to obtain the immobilized enzyme lx-EstM160K. Additionally, lx-EstM160K showed enhanced T1/2 of 36.8 h at 70 °C in comparison to free enzyme. lx-EstM160K could degrade various pyrethroid pesticides. After 40 min reaction with 50 U of the lx-EstM160K, the malathion removal was 95.8% with a malathion concentration of 20 mg/L. When 2.5 g lx-EstM160K was added to the 10 mL column reactor with the concentration of bifenthrin was 500 mg/L and the transfer rate of the pump was 0.7 mL/min, the degradation rate of lx-EstM160K to bifenthrin was 90.4%. lx-EstM160K exhibited high operational stability and maintained 72% initial activity after ten batches of continuous reaction for bifenthrin pesticide biodegradation. Full article
(This article belongs to the Special Issue Biocatalysts and Their Environmental Applications)
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Review

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Open AccessReview
Overview of Recent Advances in Immobilisation Techniques for Phenol Oxidases in Solution
Catalysts 2020, 10(5), 467; https://doi.org/10.3390/catal10050467 - 25 Apr 2020
Abstract
Over the past two decades, phenol oxidases, particularly laccases and tyrosinases, have been extensively used for the removal of numerous pollutants in wastewaters due to their broad substrate specificity and their ability to use readily accessible molecular oxygen as the essential cofactor. As [...] Read more.
Over the past two decades, phenol oxidases, particularly laccases and tyrosinases, have been extensively used for the removal of numerous pollutants in wastewaters due to their broad substrate specificity and their ability to use readily accessible molecular oxygen as the essential cofactor. As for other enzymes, immobilisation of laccases and tyrosinases has been shown to improve the performance and efficiency of the biocatalysts in solution. Several reviews have addressed the enzyme immobilisation techniques and the application of phenol oxidases to decontaminate wastewaters. This paper offers an overview of the recent publications, mainly from 2012 onwards, on the various immobilisation techniques applied to laccases and tyrosinases to induce and/or increase the performance of the biocatalysts. In this paper, the emphasis is on the efficiencies achieved, in terms of structural modifications, stability and resistance to extreme conditions (pH, temperature, inhibitors, etc.), reactivity, reusability, and broad substrate specificity, particularly for application in bioremediation processes. The advantages and disadvantages of several enzyme immobilisation techniques are also discussed. The relevance and effectiveness of the immobilisation techniques with respect to wastewater decontamination are critically assessed. A perspective on the future directions for large-scale application of the phenol oxidases in immobilised forms is provided. Full article
(This article belongs to the Special Issue Biocatalysts and Their Environmental Applications)
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Other

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Open AccessPerspective
The Current State of Research on PET Hydrolyzing Enzymes Available for Biorecycling
Catalysts 2021, 11(2), 206; https://doi.org/10.3390/catal11020206 - 03 Feb 2021
Abstract
This short paper reviews two groups of enzymes designated as polyethylene terephthalate (PET) hydrolases: one consists of thermophilic cutinases from thermophilic microorganisms (actinomycetes and a fungus) and the other consists of mesophilic cutinases, the representative of which is IsPETase from a mesophilic [...] Read more.
This short paper reviews two groups of enzymes designated as polyethylene terephthalate (PET) hydrolases: one consists of thermophilic cutinases from thermophilic microorganisms (actinomycetes and a fungus) and the other consists of mesophilic cutinases, the representative of which is IsPETase from a mesophilic bacterium. From the viewpoint that PET hydrolysis requires a high temperature close to the glass transition temperature (65–70 °C in water) of PET, mesophilic cutinases are not suitable for use in the enzymatic recycling of PET since their degradation level is one to three orders of magnitude lower than that of thermophilic cutinases. Many studies have attempted to increase the thermostability of IsPETase by introducing mutations, but even with these modifications, the mesophilic cutinase does not reach the same level of degradation as thermophilic cutinases. In addition, this kind of trial contradicts the claim that IsPETase works at ambient temperature. As plastic pollution is an urgent environmental issue, scientists must focus on feasible thermophilic enzymes for the enzymatic processing of disposed PET, rather than on mesophilic cutinases. Thermophilic and mesophilic cutinases must be evaluated precisely and comparatively, based on their features that enable them to hydrolyze PET, with the aim of enzymatic PET disposal. The level of thermophilic cutinases has already reached their optimal level in PET biorecycling. The optimal level may be reached through the processing of PET waste, by amorphization and micronization into readily hydrolysable forms and the improvement of PET hydrolases by engineering higher degradation ability and low-cost production. Here I summarize the critical points in the evaluation of PET hydrolases and discuss the biorecycling of PET. Full article
(This article belongs to the Special Issue Biocatalysts and Their Environmental Applications)
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