Hydrogels are 3D hydrophilic polymer networks that absorb and hold huge amounts of water. Although hydrogels have traditionally been synthesized using chemical and physical methods, rapid ...developments in enzyme technology that, like chemical-based methods, enable the formation of stable covalent bonds are fast emerging as alternative ‘green catalyst’ tools. Enzymes show great potential for the synthesis of complex multifunctional wound dressing hydrogels (WDHs) ex situ and in situ as well as in acting as interactive molecules to promote the wound healing process. This review presents advances in the use of enzymes to synthesize WDHs and their fascinating role as bioactive molecules promoting the wound healing process, preventing microbial infection, and providing in situ, in-built infection-detection and diagnostic systems.
Enzymes are versatile catalysts for ex situ and in situ synthesis of wound dressing hydrogels (WDHs).
Enzymes in WDH prevent microbial infection and colonization of the wound.
Enzymes as bioactive molecules in WDHs promote wound healing.
Enzymes can serve as in situ microbial infection and diagnostic systems in WDHs.
The formation of bacterial biofilms on indwelling medical devices generally causes high risks for adverse complications such as catheter-associated urinary tract infections. In this work, a strategy ...for synthesizing innovative coatings of poly(dimethylsiloxane) (PDMS) catheter material, using layer-by-layer assembly with three novel functional polymeric building blocks, is reported, i.e., an antifouling copolymer with zwitterionic and quaternary ammonium side groups, a contact biocidal derivative of that polymer with octyl groups, and the antibacterial hydrogen peroxide (H2O2) producing enzyme cellobiose dehydrogenase (CDH). CDH oxidizes oligosaccharides by transferring electrons to oxygen, resulting in the production of H2O2. The design and synthesis of random copolymers which combine segments that have antifouling properties by zwitterionic groups and can be used for electrostatically driven layer-by-layer (LbL) assembly at the same time were based on the atom-transfer radical polymerization of dimethylaminoethyl methacrylate and subsequent partial sulfobetainization with 1,3-propane sultone followed by quaternization with methyl iodide only or octyl bromide and thereafter methyl iodide. The alternating multilayer systems were formed by consecutive adsorption of the novel polycations with up to 50% zwitterionic groups and of poly(styrenesulfonate) as the polyanion. Due to its negative charge, enzyme CDH was also firmly embedded as a polyanionic layer in the multilayer system. This LbL coating procedure was first performed on prefunctionalized silicon wafers and studied in detail with ellipsometry as well as contact angle (CA) and zetapotential (ZP) measurements before it was transferred to prefunctionalized PDMS and analyzed by CA and ZP measurements as well as atomic force microscopy. The coatings comprising six layers were stable and yielded a more neutral and hydrophilic surface than did PDMS, the polycation with 50% zwitterionic groups having the largest effect. Enzyme activity was found to be dependent on the depth of embedment in the multilayer coating. Depending on the used polymeric building block, up to a 60% reduction in the amount of adhering bacteria and clear evidence for killed bacteria due to the antimicrobial functionality of the coating could be confirmed. Overall, this work demonstrates the feasibility of an easy to perform and shape-independent method for preparing an antifouling and antimicrobial coating for the significant reduction of biofilm formation and thus reducing the risk of acquiring infections by using urinary catheters.
The urge to discover and develop new technologies for closing the plastic carbon cycle is motivating industries, governments, and academia to work closely together to find suitable solutions in a ...timely manner. In this review article, a combination of uprising breakthrough technologies is presented highlighting their potential and complementarity to be integrated one with the other, therefore providing a potential solution to efficiently solve the plastics problem. First, modern approaches for bio-exploration and engineering of polymer-active enzymes are presented to degrade polymers into valuable building blocks. Special focus is placed on the recovery of components from multilayered materials since these complex materials can only be recycled insufficiently or not at all by existing technologies. Then, the potential of microbes and enzymes for resynthesis of polymers and reuse of building blocks is summarized and discussed. Finally, examples for improvement of the bio-based content and enzymatic degradability and future perspectives are given.
•Approaches for bioexploration of polymer-active enzymes.•Recovery of monomers from multi-layered materials.•Microbes and enzymes for resynthesis of polymers.
Chitosan, a copolymer of glucosamine and N-acetyl glucosamine, is derived from chitin. Chitin is found in cell walls of crustaceans, fungi, insects and in some algae, microorganisms, and some ...invertebrate animals. Chitosan is emerging as a very important raw material for the synthesis of a wide range of products used for food, medical, pharmaceutical, health care, agriculture, industry, and environmental pollution protection. This review, in line with the focus of this special issue, provides the reader with (1) an overview on different sources of chitin, (2) advances in techniques used to extract chitin and converting it into chitosan, (3) the importance of the inherent characteristics of the chitosan from different sources that makes them suitable for specific applications and, finally, (4) briefly summarizes ways of tailoring chitosan for specific applications. The review also presents the influence of the degree of acetylation (DA) and degree of deacetylation (DDA), molecular weight (Mw) on the physicochemical and biological properties of chitosan, acid-base behavior, biodegradability, solubility, reactivity, among many other properties that determine processability and suitability for specific applications. This is intended to help guide researchers select the right chitosan raw material for their specific applications.
Certain members of the carboxylesterase superfamily can act at the interface between water and water-insoluble substrates. However, nonnatural bulky polyesters usually are not efficiently hydrolyzed. ...In the recent years, the potential of enzyme engineering to improve hydrolysis of synthetic polyesters has been demonstrated. Regions on the enzyme surface have been modified by using site-directed mutagenesis in order to tune sorption processes through increased hydrophobicity of the enzyme surface. Such modifications can involve specific amino acid substitutions, addition of binding modules, or truncation of entire domains improving sorption properties and/or dynamics of the enzyme. In this review, we provide a comprehensive overview on different strategies developed in the recent years for enzyme surface engineering to improve the activity of polyester-hydrolyzing enzymes.
Of the 25 million tons of plastic waste produced every year in Europe, 40% of these are not reused or recycled, thus contributing to environmental pollution, one of the major challenges of the 21st ...century. Most of these plastics are made of petrochemical-derived polymers which are very difficult to degrade and as a result, a lot of research efforts have been made on more environmentally friendly alternatives.
Bio-based monomers, derived from renewable raw materials, constitute a possible solution for the replacement of oil-derived monomers, with furan derivatives that emerged as platform molecules having a great potential for the synthesis of biobased polyesters, polyamides and their copolymers.
This review article summarizes the latest developments in biotechnological production of furan compounds that can be used in polymer chemistry as well as in their conversion into polymers. Moreover, the biodegradability of the resulting materials is discussed.
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•Biotechnological production of furan derivatives for polymerization reactions.•Biotechnological and chemical synthesis of furan-based polymers.•Enzymatic degradability of the furan-based polyesters.
Lignin, a structural component of lignocellulosic plants, is an alternative raw material with enormous potential to replace diminishing fossil-based resources for the sustainable production of many ...chemicals and materials. Unfortunately, lignin’s heterogeneity, low reactivity, and strong intra- and intermolecular hydrogen interactions and modifications introduced during the pulping process present significant technical challenges. However, the increasing ability to tailor lignin biosynthesis pathways by targeting enzymes and the continued discovery of more robust biocatalysts are enabling the synthesis of novel valuable products. This review summarizes how enzymes involved in lignin biosynthesis pathways and microbial enzymes are being harnessed to produce chemicals and materials and to upgrade lignin properties for the synthesis of a variety of value-added lignin industrial products.
Lignin is a versatile alternative industrial raw material.The enzymes involved in lignin biosynthesis can be engineered to produce industrially relevant raw materials.The lignin transformation machinery in microorganisms can be exploited to produce a variety of industrially relevant raw materials.Enzymes increase lignin reactivity and miscibility with other polymers.Enzymes are useful biocatalysts for upgrading technical lignin properties for the production of functional materials.
The polymer industry is under pressure to mitigate the environmental cost of petrol-based plastics. Biotechnologies contribute to the gradual replacement of petrol-based chemistry and the development ...of new renewable products, leading to the closure of carbon circle. An array of bio-based building blocks is already available on an industrial scale and is boosting the development of new generations of sustainable and functionally competitive polymers, such as polylactic acid (PLA). Biocatalysts add higher value to bio-based polymers by catalyzing not only their selective modification, but also their synthesis under mild and controlled conditions. The ultimate aim is the introduction of chemical functionalities on the surface of the polymer while retaining its bulk properties, thus enlarging the spectrum of advanced applications.
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•Thc_Cut1 hydrolyzes PET in polymer blends without prior separation.•Significant inhibitory effect of soluble released products is detectable.•Main process influencing factors are ...particle size, temperature & enzyme stability.
In this study we investigated the ability of a cutinase from Thermobifida cellulosilytica (Thc_Cut1) to hydrolyze poly (ethylene terephthalate) (PET) moieties in different polymer blends. The composition of various materials including commercial available bottles and packaging was determined using Fourier Transform InfraRed spectroscopy (FT-IR) and Differential Scanning Calorimetry (DSC). When incubated with PET blended with polyethylene (PE) or polyamide (PA) from packaging and bottles without prior separation, Thc_Cut1 selectively hydrolyzed the PET moieties releasing terephthalic acid (TPA) and mono(2-hydroxyethyl) terephthalate (MHET). Polymer blends were hydrolyzed in an up to 9 times higher extent compared to higher crystalline pure PET. The influence of various parameters like temperature, particle size, crystallinity and product inhibition on hydrolysis of PET moieties by Thc_Cut1 was investigated. The amount of products released was up to 10 times higher when the incubation temperature was increased from 40°C to 60°C. The smaller the particle size the higher the hydrolysis rates were. Interestingly, semi-crystalline (24%) PET from bottles was hydrolyzed faster than powder from amorphous PET films (12%). An inhibitory effect of bis(2-hydroxyethyl) terephthalate (BHET) on hydrolysis of PET by Thc_Cut1 was observed.
Enzymatic hydrolysis of poly(1,4-butylene 2,5-thiophenedicarboxylate) (PBTF) and poly(1,4-butylene 2,5-furandicarboxylate) (PBF) by Humicola insolens (HiC) and Thermobifida cellulosilytica (Cut) ...cutinases is investigated. For the first time, the different depolymerization mechanisms of PBTF (endo-wise scission) and PBF (exo-wise cleavage) has been unveiled and correlated to the chemical structure of the two polyesters.
•PBF and PBTF were successfully hydrolyzed by cutinase enzymes.•Weight losses of about 20% have been reached after only 72 h of incubation.•Different depolymerization mechanisms of PBTF (endo-wise scission) and PBF (exo-wise cleavage) were unveiled.
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