Special Issue "Enzymatic Synthesis and Characterization of Polymers"

A special issue of Processes (ISSN 2227-9717). This special issue belongs to the section "Materials Processes".

Deadline for manuscript submissions: closed (31 December 2020).

Special Issue Editors

Prof. Dr. Francisc Peter
E-Mail Website
Guest Editor
Department of Applied Chemistry and Engineering of Organic and Natural Compounds, University Politehnica of Timisoara, 300001 Timisoara, Romania
Interests: biocatalysis; enzyme immobilization; sol–gel entrapment; enzymatic polymer synthesis; bioproducts; bioconjugates; lipase; enzymatic kinetic resolution; copolyesters
Dr. Carmen Boeriu
E-Mail Website
Guest Editor
Department of Biobased Products, Wageningen Food & Biobased Research, 6708 WG Wageningen, The Netherlands
Interests: applied biocatalysis; enzymatic polymerization; enzymatic cascade reactions; biopolymers; polyesters; biomonomers; polysaccharides; proteins; lignin; lipases; oxidative enzymes; polymer characterization; function–structure relationships

Special Issue Information

Dear Colleagues,

Alongside the well-known biopolymers synthesized by microorganisms, a remarkable development was noticed in the past decades for the utilization of isolated enzymes as green alternatives in polymer science. Particularly, the conversion of renewable monomers in environmentally benign polymeric materials, such as polyesters and polyamides, has become an emerging topic. The exceptional catalytic power and selectivity of the enzymes open tremendous possibilities to carry out polymerization reactions in vitro.

The Special Issue “Enzymatic synthesis of polymers” will focus on the latest developments in the field of biocatalytic in vitro synthesis of new polymeric and oligomeric compounds in various reaction media, fine tuning of the enzyme polymerization specificity by immobilization, as well as advanced methods of process monitoring, characterization, and utilization of the synthesized polymers and copolymers. Original papers and reviews are welcome in the following main (but not exclusive) topics:

  • Utilization of bio-based resources for sustainable enzymatic polymer synthesis;
  • Advancement in the capability of isolated enzymes to catalyze polymerization and copolymerization reactions in vitro;
  • New block copolymers by chemoenzymatic processes;
  • The role of immobilization for improving the process parameters and allowing continuous processes;
  • Utilization of ionic liquids, deep eutectic solvents, and other nonconventional reaction media for enzymatic polymerizations in vitro;
  • Modification of carbohydrates and lignin-based compounds by enzyme-catalyzed polymerization;
  • Utilization of MALDI-TOF MS, NMR, and other instrumental techniques for the elucidation of the mechanism of polymerization/copolymerization and structural characterization of the new polymeric compounds.

Prof. Francisc Peter
Dr. Carmen Boeriu
Guest Editors

Manuscript Submission Information

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

  • Biocatalytic polymerization
  • Bio-based oligomers
  • Bio-based polymers
  • Immobilized and engineered enzymes
  • Nonconventional reaction media
  • Green polymerization pathways
  • Polymer characterization
  • Chemoenzymatic polymer synthesis

Published Papers (7 papers)

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Research

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Article
Enzymatic Synthesis of Poly(alkylene succinate)s: Influence of Reaction Conditions
Processes 2021, 9(3), 411; https://0-doi-org.brum.beds.ac.uk/10.3390/pr9030411 - 25 Feb 2021
Cited by 3 | Viewed by 606
Abstract
Application of lipases (preferentially Candida antarctica Lipase B, CALB) for melt polycondensation of aliphatic polyesters by transesterification of activated dicarboxylic acids with diols allows to displace toxic metal and metal oxide catalysts. Immobilization of the enzyme enhances the activity and the temperature range [...] Read more.
Application of lipases (preferentially Candida antarctica Lipase B, CALB) for melt polycondensation of aliphatic polyesters by transesterification of activated dicarboxylic acids with diols allows to displace toxic metal and metal oxide catalysts. Immobilization of the enzyme enhances the activity and the temperature range of use. The possibility to use enzyme-catalyzed polycondensation in melt is studied and compared to results of polycondensations in solution. The experiments show that CALB successfully catalyzes polycondensation of both, divinyladipate and dimethylsuccinate, respectively, with 1,4-butanediol. NMR spectroscopy, relative molar masses obtained by size exclusion chromatography, MALDI-TOF MS and wide-angle X-ray scattering are employed to compare the influence of synthesis conditions for poly(butylene adipate) (PBA) and poly(butylene succinate) (PBS). It is shown that the enzymatic activity of immobilized CALB deviates and influences the molar mass. CALB-catalyzed polycondensation of PBA in solution for 24 h at 70 °C achieves molar masses of up to Mw~60,000 g/mol, higher than reported previously and comparable to conventional PBA, while melt polycondensation resulted in a moderate decrease of molar mass to Mw~31,000. Enzymatically catalyzed melt polycondensation of PBS yields Mw~23,400 g/mol vs. Mw~40,000 g/mol with titanium(IV)n-butoxide. Melt polycondensation with enzyme catalysis allows to reduce the reaction time from days to 3–4 h. Full article
(This article belongs to the Special Issue Enzymatic Synthesis and Characterization of Polymers)
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Article
Biocatalytic Approach for Novel Functional Oligoesters of ε-Caprolactone and Malic Acid
Processes 2021, 9(2), 232; https://0-doi-org.brum.beds.ac.uk/10.3390/pr9020232 - 26 Jan 2021
Cited by 1 | Viewed by 653
Abstract
Biocatalysis has developed in the last decades as a major tool for green polymer synthesis. The particular ability of lipases to catalyze the synthesis of novel polymeric materials has been demonstrated for a large range of substrates. In this work, novel functional oligoesters [...] Read more.
Biocatalysis has developed in the last decades as a major tool for green polymer synthesis. The particular ability of lipases to catalyze the synthesis of novel polymeric materials has been demonstrated for a large range of substrates. In this work, novel functional oligoesters were synthesized from ε-caprolactone and D,L/L-malic acid by a green and sustainable route, using two commercially available immobilized lipases as catalysts. The reactions were carried out at different molar ratios of the comonomers in organic solvents, but the best results were obtained in solvent-free systems. Linear and cyclic oligomeric products with average molecular weights of about 1500 Da were synthesized, and the formed oligoesters were identified by matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) analysis. The oligoester synthesis was not enantioselective in the studied reaction conditions. The operational stability of both biocatalysts (Novozyme 435 and GF-CalB-IM) was excellent after reutilization in 13 batch reaction cycles. The thermal properties of the reaction products were investigated by thermogravimetric (TG) and differential scanning calorimetry (DSC) analysis. The presence of polar pendant groups in the structure of these oligomers could widen the possible applications compared to the oligomers of ε-caprolactone or allow the conversion to other functional materials. Full article
(This article belongs to the Special Issue Enzymatic Synthesis and Characterization of Polymers)
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Article
Chemoenzymatic Synthesis of New Aromatic Esters of Mono- and Oligosaccharides
Processes 2020, 8(12), 1638; https://0-doi-org.brum.beds.ac.uk/10.3390/pr8121638 - 11 Dec 2020
Cited by 2 | Viewed by 799
Abstract
An efficient and convenient chemoenzymatic route for the synthesis of novel phenolic mono-, di- and oligosaccharide esters is described. Acetal derivatives of glucose, sucrose, lactose and inulin were obtained by chemical synthesis. The fully characterized pure sugar acetals were subjected to enzymatic esterification [...] Read more.
An efficient and convenient chemoenzymatic route for the synthesis of novel phenolic mono-, di- and oligosaccharide esters is described. Acetal derivatives of glucose, sucrose, lactose and inulin were obtained by chemical synthesis. The fully characterized pure sugar acetals were subjected to enzymatic esterification with 3-(4-hydroxyphenyl) propionic acid (HPPA) in the presence of Novozyme 435 lipase as a biocatalyst. The aromatic esters of alkyl glycosides and glucose acetal were obtained with good esterification yields, characterized by mass spectrometry (MALDI-TOF MS), infrared spectroscopy (FTIR) and nuclear magnetic resonance spectroscopy (1H NMR, 13C NMR). The synthesis of aromatic esters of disaccharide acetals was successful only for the enzymatic esterification of sucrose acetal. The new chemoenzymatic route allowed the synthesis of novel aromatic esters of inulin as the inulin monoacetal monoester and diester and the inulin diacetal monoester with a polymerization degree of two, as well as the inulin monoacetal monoester with a degree of polymerization of three, were obtained by enzymatic acylation of inulin acetals with HPPA. These compounds could represent a new class of sugar ester surfactants with enhanced bioactivity, antioxidative and antimicrobial properties and with potential application in drug delivery systems. Full article
(This article belongs to the Special Issue Enzymatic Synthesis and Characterization of Polymers)
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Article
Thermostable α-Glucan Phosphorylase-Catalyzed Enzymatic Copolymerization to Produce Partially 2-Deoxygenated Amyloses
Processes 2020, 8(9), 1070; https://0-doi-org.brum.beds.ac.uk/10.3390/pr8091070 - 01 Sep 2020
Cited by 1 | Viewed by 667
Abstract
α-Glucan phosphorylase catalyzes the enzymatic polymerization of α-d-glucose 1-phosphate (Glc-1-P) monomers from a maltooligosaccharide primer to produce α(1→4)-glucan—i.e., amylose. In this study, by exploiting the weak specificity for the substrate recognition of a thermostable α-glucan phosphorylase (from [...] Read more.
α-Glucan phosphorylase catalyzes the enzymatic polymerization of α-d-glucose 1-phosphate (Glc-1-P) monomers from a maltooligosaccharide primer to produce α(1→4)-glucan—i.e., amylose. In this study, by exploiting the weak specificity for the substrate recognition of a thermostable α-glucan phosphorylase (from Aquifex aeolicus VF5), we investigated the enzymatic copolymerization of 2-deoxy-α-d-glucose 1-phosphate (dGlc-1-P), which was produced in situ from d-glucal, with Glc-1-P to obtain non-natural heteropolysaccharides composed of α(1→4)-linked dGlc/Glc units—i.e., partially 2-deoxygenated amylose. The reactions were carried out at different monomer feed ratios using a maltotriose primer at 40 °C for 24 h. The products were precipitated from the reaction medium, isolated by centrifugation, and subjected to 1H NMR spectroscopic and powder X-ray diffraction measurements to evaluate their chemical and crystalline structures, respectively. Owing to its amorphous nature, the partially 2-deoxygenated amylose with adapted unit ratios formed a film when subjected to a casting method. Full article
(This article belongs to the Special Issue Enzymatic Synthesis and Characterization of Polymers)
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Article
Cross-Linking of Wheat Bran Arabinoxylan by Fungal Laccases Yields Firm Gels
Processes 2020, 8(1), 36; https://0-doi-org.brum.beds.ac.uk/10.3390/pr8010036 - 30 Dec 2019
Cited by 5 | Viewed by 1237
Abstract
The native extractable arabinoxylans (AX) from wheat bran were cross-linked by the commercial laccase C (LccC) and self-produced laccases from Funalia trogii (LccFtr) and Pleurotus pulmonarius (LccPpu) (0.04 U/µg FA, each). Dynamic oscillation measurements of the 6% AX gels demonstrated a storage modulus [...] Read more.
The native extractable arabinoxylans (AX) from wheat bran were cross-linked by the commercial laccase C (LccC) and self-produced laccases from Funalia trogii (LccFtr) and Pleurotus pulmonarius (LccPpu) (0.04 U/µg FA, each). Dynamic oscillation measurements of the 6% AX gels demonstrated a storage modulus of 9.4 kPa for LccC, 9.8 kPa for LccFtr, and 10.0 kPa for LccPpu. A loss factor ≤ 0.6 was recorded in the range from 20 to 80 Hz for all three laccases, and remained constant for four weeks of storage, when LccFtr and LccPpu were used. Arabinoxylan gel characteristics, including high water holding capacity, swelling ratio in saliva, and heat resistance indicated a covalently cross-linked network. Neither the mediator compounds caffeic acid and 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid (ABTS), nor citrus pectin, enhanced the elastic properties of the gels. Using laccases as an oxidant provided gels with a solid and stable texture, comparable in firmness to traditional gelatin gels. Thus, AX gels can be presented in the vegan, halal, and kosher food markets. They may also find use in pharmaceutical and other industrial applications. Full article
(This article belongs to the Special Issue Enzymatic Synthesis and Characterization of Polymers)
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Article
Cross-Linking of Fibrex Gel by Fungal Laccase: Gel Rheological and Structural Characteristics
Processes 2020, 8(1), 16; https://0-doi-org.brum.beds.ac.uk/10.3390/pr8010016 - 20 Dec 2019
Cited by 7 | Viewed by 1134
Abstract
Sugar beet fibre (fibrex) is an abundant side-stream from the sugar refining industry. A self-produced laccase from Funalia trogii (LccFtr) (0.05 U/µg FA) successfully cross-linked fibrex to an edible gel. Dynamic oscillation measurements of the 10% fibrex gels showed a storage modulus of [...] Read more.
Sugar beet fibre (fibrex) is an abundant side-stream from the sugar refining industry. A self-produced laccase from Funalia trogii (LccFtr) (0.05 U/µg FA) successfully cross-linked fibrex to an edible gel. Dynamic oscillation measurements of the 10% fibrex gels showed a storage modulus of 5.52 kPa and loss factors ≤ 0.36 in the range from 20 to 80 Hz. Comparing storage stability of sweetened 10% fibrex gels with sweetened commercial 6% gelatin gels (10% and 30% d-sucrose) indicated a constant storage modulus and loss factors ≤ 0.7 during four weeks of storage in fibrex gels. Loss factors of sweetened gelatin gels were ≤0.2, and their storage modulus decreased from 9 to 7 kPa after adding d-sucrose and remained steady for four weeks of storage. Fibrex gel characteristics, including high water holding capacity, swelling ratio in saliva, and heat resistance are attributed to a covalently cross-linked network. Vanillin, as a mediator, and citrus pectin did not enhance covalent cross-links and elastic properties of the fibrex gels. Thus, laccase as an oxidative agent provided gels with a solid and stable texture. Fibrex gels may find uses in pharmaceutical and other industrial applications, which require a heat-resistant gel that forms easily at room temperature. They also represent an ethical alternative for manufacturing vegan, halal, and kosher food. Full article
(This article belongs to the Special Issue Enzymatic Synthesis and Characterization of Polymers)
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Review

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Review
Achievements and Trends in Biocatalytic Synthesis of Specialty Polymers from Biomass-Derived Monomers Using Lipases
Processes 2021, 9(4), 646; https://0-doi-org.brum.beds.ac.uk/10.3390/pr9040646 - 07 Apr 2021
Cited by 3 | Viewed by 906
Abstract
New technologies for the conversion of biomass into high-value chemicals, including polymers and plastics, is a must and a challenge. The development of green processes in the last decade involved a continuous increase of the interest towards the synthesis of polymers using in [...] Read more.
New technologies for the conversion of biomass into high-value chemicals, including polymers and plastics, is a must and a challenge. The development of green processes in the last decade involved a continuous increase of the interest towards the synthesis of polymers using in vitro biocatalysis. Among the remarkable diversity of new bio-based polymeric products meeting the criteria of sustainability, biocompatibility, and eco-friendliness, a wide range of polyesters with shorter chain length were obtained and characterized, targeting biomedical and cosmetic applications. In this review, selected examples of such specialty polymers are presented, highlighting the recent developments concerning the use of lipases, mostly in immobilized form, for the green synthesis of ε-caprolactone co-polymers, polyesters with itaconate or furan units, estolides, and polyesteramides. The significant process parameters influencing the average molecular weights and other characteristics are discussed, revealing the advantages and limitations of biocatalytic processes for the synthesis of these bio-based polymers. Full article
(This article belongs to the Special Issue Enzymatic Synthesis and Characterization of Polymers)
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