Dehydration reactions proceed readily in water-filled biological cells. Development of biocatalysts that mimic such compartmentalized reactions has been cumbersome due to the lack of low-cost ...nanomaterials and associated technologies. Here we show that cationic lignin nanospheres function as activating anchors for hydrolases, and enable aqueous ester synthesis by forming spatially confined biocatalysts upon self-assembly and drying-driven aggregation in calcium alginate hydrogel. Spatially confined microbial cutinase and lipase retain 97% and 70% of their respective synthetic activities when the volume ratio of water to hexane increases from 1:1 to 9:1 in the reaction medium. The activity retention of industrially most frequently used acrylic resin-immobilized Candida antarctica lipase B is only 51% under similar test conditions. Overall, our findings enable fabrication of robust renewable biocatalysts for aqueous ester synthesis, and provide insight into the compartmentalization of diverse heterogeneous catalysts.
Following concerns over increasing global plastic pollution, interest in the production and characterization of bio-based and biodegradable alternatives is rising. In the present work, the synthesis ...of a series of fully bio-based alternatives based on 2,4-, 2,5-, and 2,6-pyridinedicarboxylic acid-derived polymers produced via enzymatic catalysis are reported. A similar series of aromatic-aliphatic polyesters based on diethyl-2,5-furandicarboxylate and of the petroleum-based diethyl terephthalate and diethyl isophthalate were also synthesized. Here we show that the enzymatic synthesis starting from 2,4-diethyl pyridinedicarboxylate leads to the best polymers in terms of molecular weights (M
= 14.3 and M
of 32.1 kDa when combined with 1,8-octanediol) when polymerized in diphenyl ether. Polymerization in solventless conditions were also successful leading to the synthesis of bio-based oligoesters that can be further functionalized. DSC analysis show a clear similarity in the thermal behavior between 2,4-diethyl pyridinedicarboxylate and diethyl isophthalate (amorphous polymers) and between 2,5-diethyl pyridinedicarboxylate and diethyl terephthalate (crystalline 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.
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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.
Polyurethanes (PU) are one of the most-used classes of synthetic polymers in Europe, having a considerable impact on the plastic waste management in the European Union. Therefore, they represent a ...major challenge for the recycling industry, which requires environmentally friendly strategies to be able to re-utilize their monomers without applying hazardous and polluting substances in the process. In this work, enzymatic hydrolysis of a polyurethane-polyester (PU-PE) copolymer using
cutinase (HiC) has been investigated in order to achieve decomposition at milder conditions and avoiding harsh chemicals. PU-PE films have been incubated with the enzyme at 50 °C for 168 h, and hydrolysis has been followed throughout the incubation. HiC effectively hydrolysed the polymer, reducing the number average molecular weight (M
) and the weight average molecular weight (M
) by 84% and 42%, respectively, as shown by gel permeation chromatography (GPC), while scanning electron microscopy showed cracks at the surface of the PU-PE films as a result of enzymatic surface erosion. Furthermore, Fourier Transform Infrared (FTIR) analysis showed a reduction in the peaks at 1725 cm
, 1164 cm
and 1139 cm
, indicating that the enzyme preferentially hydrolysed ester bonds, as also supported by the nuclear magnetic resonance spectroscopy (NMR) results. Liquid chromatography time-of-flight/mass spectrometry (LC-MS-Tof) analysis revealed the presence in the incubation supernatant of all of the monomeric constituents of the polymer, thus suggesting that the enzyme was able to hydrolyse both the ester and the urethane bonds of the polymer.
In the present work, different hydrolases were adsorbed onto polypropylene beads to investigate their activity both in short-esters and polyesters synthesis. The software MODDE® Pro 13 (Sartorius) ...was used to develop a full-factorial design of experiments (DoE) to analyse the thermostability and selectivity of the immobilized enzyme towards alcohols and acids with different chain lengths in short-esters synthesis reactions. The temperature optima of Candida antarctica lipase B (CaLB), Humicola insolens cutinase (HiC), and Thermobifida cellulosilytica cutinase 1 (Thc_Cut1) were 85 °C, 70 °C, and 50 °C. CaLB and HiC preferred long-chain alcohols and acids as substrate in contrast to Thc_Cut1, which was more active on short-chain monomers. Polymerization of different esters as building blocks was carried out to confirm the applicability of the obtained model on larger macromolecules. The selectivity of both CaLB and HiC was investigated and best results were obtained for dimethyl sebacate (DMSe), leading to polyesters with a Mw of 18 kDa and 6 kDa. For the polymerization of dimethyl adipate (DMA) with BDO and ODO, higher molecular masses were obtained when using CaLB onto polypropylene beads (CaLB_PP) as compared with CaLB immobilized on macroporous acrylic resin beads (i.e., Novozym 435). Namely, for BDO the Mn were 7500 and 4300 Da and for ODO 8100 and 5000 Da for CaLB_PP and for the commercial enzymes, respectively. Thc_Cut1 led to polymers with lower molecular masses, with Mn < 1 kDa. This enzyme showed a temperature optimum of 50 °C with 63% of DMA and BDO when compared to 54% and 27%, at 70 °C and at 85 °C, respectively.
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•Enzyme catalysed hydrolysis of fibre surface is monitored by nanoscale thermal analysis.•Amorphous surface region is selectively hydrolysed due to limited access of enzyme to fibre ...core.•Defined bio-based fibres with highly crystalline surface is designed by environmentally friendly white biotech process.
Enzyme catalysed hydrolysis of bio-based poly(lactic acid) (PLA) represents an environmentally-friendly route for a controlled modification of polymer fibres. In this work, the topochemical hydrolysis reaction of cutinase from Humicola insolens (HiC) on PLA fibre was mechanistically investigated using the advanced surface sensitive nanoscale thermal analysis (nano-TA) technique. The enzymatic hydrolysis preferentially occurs at the amorphous regions of the fibre outer layer, thus leading to randomised hydrolysis, monomer release and ablation of the fibre surface during the initial phase of the hydrolysis. Due to the higher hydrolysis rate at amorphous regions, the crystallinity of the fibre outer layer increases. As a result, an enrichment in overall fibre crystallinity is observed by increased melting enthalpy. The accessibility of the enzyme to the fibre core is restricted, thus the change in crystallinity is prevalent on the fibre outer region. The observed increase of the surface softening temperature from the glass transition temperature close to the melting on-set of crystalline PLA as detected by nano-TA supports the hypothesis, that selective hydrolysis preferably takes place at the amorphous region at the fibre outer layer, thus leading to modified PLA fibres with an unchanged fibre core and a very thin and highly crystalline surface layer.
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