Peroxidase-catalyzed copolymerization of syringaldehyde and bisphenol A

A Novel Method of Self-Cross-Linking of Syringaldehyde with Activated Methoxy Groups via Cross-Coupling for Lignin-Based Wood Adhesives

As steric hindrance, methoxy groups are limiting the valorization of hardwood lignin. This paper reports a novel method of self-cross-linking of the syringaldehyde with activated methoxy groups (-OCH3) via cross-coupling reaction to obtain thermosetting polymers for lignin-based wood adhesives. The methoxy groups of syringaldehyde have been activated via cross-coupling reaction by substituting Ar-OCH3 with Ar-CH2-SiMe3, and dichloromethane, leading to cross-linking via methylene bridges to build a thermosetting polymer. FTIR spectra showed a decrease in the intensity of a -CH3 and -OH group, owing to the substitution of the methoxy group. 13C NMR spectra also supported these results with the -SiMe3 signal that disappeared after the cross-linking reaction. Furthermore, cross-linking between the activated methoxy groups was confirmed with a strong exothermic peak at 130 °C, resulting in an increase in the adhesion strength as hot-pressing temperature increased from 160 to 180 °C. These results suggest that the cross-linking between the activated methoxy groups of syringaldehyde is an important understanding of valorizing hardwood lignin via building thermosetting polymers for lignin-based adhesives.

Recent Advances in Renewable Polymer Production from Lignin-Derived Aldehydes

Lignin directly derived from lignocellulosic biomass has been named a promising source of platform chemicals for the production of bio-based polymers. This review discusses potentially relevant routes to produce renewable aromatic aldehydes (e.g., syringaldehyde and vanillin) from lignin feedstocks (pre-isolated lignin or lignocellulose) that are used to synthesize a range of bio-based polymers. To do this, the processes to make aromatic aldehydes from lignin with their highest available yields are first presented. After that, the routes from such aldehydes to different polymers are explored. Challenges and perspectives of the production the lignin-derived renewable chemicals and polymers are also highlighted.

Removal of bisphenol A and its derivatives from aqueous medium through laccase-catalyzed treatment enhanced by addition of polyethylene glycol

In this study, enzymatic removal of bisphenol A (BPA) from the aqueous medium was investigated through the generation of water-insoluble oligomers, and this procedure was applied to removal of bisphenol derivatives. The experimental parameters, such as the temperature, pH value, enzyme concentration, and concentration and molecular weight of polyethylene glycol (PEG), were determined for the laccase-catalyzed treatment of BPA. The optimum conditions were determined to be pH 7.0 and 40°C in the absence of PEG. Water-insoluble oligomers generated under these conditions were readily removed by filtration or centrifugation. The optimum pH value was decreased to 5.0 in the presence of PEG and the laccase dose was reduced to one-fiftieth of that in the absence of PEG. This indicates that the addition of PEG protects the enzymatic activity and prevents capture of laccase molecules in the oligomers. The oligomers generated in the presence of PEG were removed from the aqueous medium by filtration with a membrane filter or by centrifugation. The oligomers were completely filtrated out with a filter paper by decreasing the pH value to 3.0. In addition, several bisphenol derivatives were also treated and subsequently removed by adjusting the laccase dose in the presence of PEG using the above procedure.

In vitro analysis of the monolignol coupling mechanism using dehydrogenative polymerization in the presence of peroxidases and controlled feeding ratios of coniferyl and sinapyl alcohol

In this study, dehydrogenative polymers (DHP) were synthesized in vitro through dehydrogenative polymerization using different ratios of coniferyl alcohol (CA) and sinapyl alcohol (SA) (10:0, 8:2, 6:4, 2:8, 0:10), in order to investigate the monolignol coupling mechanism in the presence of horseradish peroxidase (HRP), Coprinus cinereus peroxidase (CiP) or soybean peroxidase (SBP) with H(2)O(2), respectively. The turnover capacities of HRP, CiP and SBP were also measured for coniferyl alcohol (CA) and sinapyl alcohol (SA), and CiP and SBP were found to have the highest turnover capacity for CA and SA, respectively. The yields of HRP-catalyzed DHP (DHP-H) and CiP-catalyzed DHP (DHP-C) were estimated between ca. 7% and 72% based on the original weights of CA/SA in these synthetic conditions. However, a much lower yield of SBP-catalyzed DHP (DHP-S) was produced compared to that of DHP-H and DHP-C. In general, the DHP yields gradually increased as the ratio of CA/SA increased. The average molecular weight of DHP-H also increased with increasing CA/SA ratios, while those of DHP-C and DHP-S were not influenced by the ratios of monolignols. The frequency of β-O-4 linkages in the DHPs decreased with increasing CA/SA ratios, indicating that the formation of β-O-4 linkages during DHP synthesis was influenced by peroxidase type.