On the Effect of Microwave Energy on Lipase-Catalyzed Polycondensation Reactions

Microwave energy (MWe) is, nowadays, widely used as a clean synthesis tool to improve several chemical reactions, such as drug molecule synthesis, carbohydrate conversion and biomass pyrolysis. On the other hand, its exploitation in enzymatic reactions has only been fleetingly investigated and, hence, further study of MWe is required to reach a precise understanding of its potential in this field. Starting from the authors’ experience in clean synthesis and biocatalyzed reactions, this study sheds light on the possibility of using MWe for enhancing enzyme-catalyzed polycondensation reactions and pre-polymer formation. Several systems and set ups were investigated involving bulk and organic media (solution phase) reactions, different enzymatic preparations and various starting bio-based monomers. Results show that MWe enables the biocatalyzed synthesis of polyesters and pre-polymers in a similar way to that reported using conventional heating with an oil bath, but in a few cases, notably bulk phase polycondensations under intense microwave irradiation, MWe leads to a rapid enzyme deactivation

Nature Inspired Solutions for Polymers: Will Cutinase Enzymes Make Polyesters and Polyamides Greener?

5siThe polymer and plastic sectors are under the urge of mitigating their environmental impact. The need for novel and more benign catalysts for polyester synthesis or targeted functionalization led, in recent years, to an increasing interest towards cutinases due to their natural ability to hydrolyze ester bonds in cutin, a natural polymer. In this review, the most recent advances in the synthesis and hydrolysis of various classes of polyesters and polyamides are discussed with a critical focus on the actual perspectives of applying enzymatic technologies for practical industrial purposes. More specifically, cutinase enzymes are compared to lipases and, in particular, to lipase B from Candida antarctica, the biocatalyst most widely employed in polymer chemistry so far. Computational and bioinformatics studies suggest that the natural role of cutinases in attacking natural polymers confer some essential features for processing also synthetic polyesters and polyamides.openopenFerrario, Valerio; Pellis, Alessandro; Cespugli, Marco; Guebitz, Georg; Gardossi, LuciaFerrario, Valerio; Pellis, Alessandro; Cespugli, Marco; Guebitz, Georg; Gardossi, Luci

Enzymatic polymerization on the surface of functionalized cellulose fibers

Enzymatic coating of functionalized cellulose fibers with catechol was performed in the presence of Trametes hirsuta laccase. Cellulose functionalization was done by covalent fixation of aromatic amines onto the cellulose surface using a dyeing procedure with C.I. Reactive Black 5 (RB5) followed by reduction with sodium hydrosulfite. Cellulase enzymes were used on coated and control samples to obtain the analytes linked with the soluble sugars in solution, to prove the reaction concepts described in this paper. Hydrolyzed coated-cellulose showed lower concentration of reducing sugars (1188 mg/L) than control samples (2011 mg/L). The structures of these compounds were checked by LC/MS analysis confirming the presence of functionalized glucose and cellobiose units coupled to poly(catechol) molecules (m/z 580 and m/z 633). Alkali extraction method showed to be very promising to coat cellulose fibers with phenols in the presence of enzymes, at mild conditions of temperature and pH

Cutinase-Catalyzed Polyester-Polyurethane Degradation: Elucidation of the Hydrolysis Mechanism

open5siPolyurethanes (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 Humicola insolens 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 degrees C for 168 h, and hydrolysis has been followed throughout the incubation. HiC effectively hydrolysed the polymer, reducing the number average molecular weight (M-n) and the weight average molecular weight (M-w) 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(-1), 1164 cm(-1) and 1139 cm(-1), 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.openDi Bisceglie, Federico; Quartinello, Felice; Vielnascher, Robert; Guebitz, Georg M.; Pellis, AlessandroDi Bisceglie, Federico; Quartinello, Felice; Vielnascher, Robert; Guebitz, Georg M.; Pellis, Alessandr

Enzymatic synthesis of biobased polyesters utilizing aromatic diols as the rigid component

In the present work, the biocatalyzed synthesis of a series of aromatic-aliphatic polyesters based on the aliphatic diesters dimethyl succinate, dimethyl adipate and dimethyl sebacate and the aromatic diols 2,5-bis(hydroxymethyl)furan, 3,4-bis(hydroxymethyl)furan and 2,6-pyridinedimethanol were investigated. A similar series of polyesters based on the petroleum-based 1,3-benzenedimethanol, 1,4-benzenedimethanol and 1,4-benzenediethanol were also synthesized for comparison. Data show that the enzymatic syntheses were successful starting from all diols, with the obtained polymers having isolated yields between 67 and over 90%, number average molecular weights between 3000 Da and 5000 Da and degree of polymerization (DP) of 6–18 (based on the used aliphatic diesters and aromatic diols) when polymerized in diphenyl ether as solvent. Only using 3,4-bis(hydroxymethyl)furan as the diol led to shorter oligomers with isolated yields around 50% and DPs of 3–5. DSC and TGA thermal analyses show clear correlation between polymer crystallinity and aliphatic carbon chain length of the diester

Bioprocessing of bamboo materials

Bamboo culms were processed using microorganisms, and fibre bundles were obtained. Bacteria and fungi with xylanase activity were isolated from the bamboo retting system. Chemical composition analysis of the fibre bundles obtained showed that the components are mainly cellulose, hemicelluloses and lignin. An increase in cellulose and hemicelluloses content was detected along with a decrease in lignin content after bio-processing. Envi-ronmental Scanning Electronic Microcopy of the fibre bundles (retted) showed great fibre sensibility towards moisture, which could significantly influence mechanical properties. Our results suggested that the bio-processing presented herein contributes to the possible development of a new means of bamboo bio-processing that can be regarded as a primary process to separate fibre bundles from non-cellulosic tissue in the culm.This work was supported by the earmarked fund for Modern Agro-industry Technology Research System (nycytx-19-E23) and the Fundamental Research Funds for the Central Universities JUSRP211A02

The Closure of the Cycle: Enzymatic Synthesis and Functionalization of Bio-Based Polyesters

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

Enzymatic colouration with laccase and peroxidases : recent progress

Enzymes have received significant attention as alternative catalysts to chemical auxiliaries in textile processing. For example, laccases and peroxidises are promising alternatives for bleaching and denim stone washing processes. Similarly, the ability to oxidise different phenolic substrates and dye precusors resulting in the formation of different coloured polymeric molecules is being exploited for developing green chemistry dyeing processes. The enzymatic process is simpler than conventional coloration processes, giving economic and environmental benefits. In this review, the applications of laccase and peroxidise enzymes in dyeing processes of various textile meterials is discussed.This work was supported by the Fundamental Research Funds for the Central Universities JUSRP211A02 and JUSRP21001; the Open Project Program of Key Laboratory of Eco-Textiles, Ministry of Education, Jiangnan University KLET1007 and the Open Project Program of State Key Laboratory for Modification of Chemical Fibers and Polymer Materials, DongHua University LK1005

Purification and mechanistic characterisation of two polygalacturonases from Sclerotium rolfsii

Sclerotium rolfsii (strain CBS 350.80) was found to produce extraordinary high amounts of polygalacturonases (PGs). Two of these extracellular enzymes were purified by a recently introduced preparative electrophoretic device (isoelectric focusing mode of free flow electrophoresis). PG 1 (39.5 kDa, pI 6.5) and PG 2 (38 kDa, pI 5.4) exhibited quite similar properties, they were found to be both endo-acting enzymes. Both PGs cleaved penta- and trigalacturonic acid while tetragalacturonic acid was only cleaved when trigalacturonic acid was present. The latter substrate was hydrolysed much faster by PG 2. Both enzymes were active on pectins with different degrees of esterification, they were sensitive towards Ca-cations and not glycosylated. The kinetic properties were measured by viscosimetry with polygalacturonic acid as a substrate. NMR experiments on a model substrate revealed an inverting mechanism of carbohydrate hydrolysis for both enzymes

Synthetic enzymes for synthetic substrates

In recent years, hydrolases like cutinases, esterases and lipases have been recognized as powerful tools for hydrolysis of synthetic polymers such as polyethylene terephthalate (PET) as an environmentally friendly alternative for environmentally harmful chemical recycling methods1. PET is currently the most common type of aromatic polyester, with widespread application as packaging material, beverage bottles, and synthetic textile fibers. So far, cutinases have been the most active enzyme class regarding PET degradation. In nature, cutinases catalyze the hydrolysis of the aliphatic biopolyester cutin, the structural component of plant cuticle. Although cutinases are able to act on natural insoluble polyesters, their activities on non-natural substrates are quit low. For this reason, different engineering strategies were established to optimize “polyesterases” for synthetic polymers (Fig.1). Thereby, development of rationale enzyme-engineering strategies led to remarkable enhancement of hydrolytic activities on polyesters and clearly showed that the affinity between the enzyme and the substrate plays a key role in the enzymatic hydrolysis of synthetic polyester. Please click Additional Files below to see the full abstract