Jute sticks biomass delignification through laccase-mediator system for enhanced saccharification and sustainable release of fermentable sugar

Jute sticks obtained after the extraction of jute fiber are an excellent biomass feedstock with a significant amount of carbohydrates that makes it an attractive resource for sustainable energy generation. However, the high lignin content in the jute stick hinders the cellulosic component of the cell wall from enzymatic hydrolysis.This work demonstrates the lignin degradation of jute stick biomass by Trametes maxima laccase in the presence of mediator Hydroxybenzotriazole and improvement in its subsequent saccharification. Lignin component in jute stick is reduced by 21.8% in a single reaction treatment with laccase-mediator compared to the untreated jute stick sample used as control. The yield of fermentable sugar is increased by 19.5% that verifies enhanced saccharification after lignin removal. Delignification of jute stick was corroborated through different analytical techniques. The Pyrolysis gas chromatography/mass spectrometry results further confirms abundance of S lignin unit in the jute stick compared to the H and G unit and modification in lignin polymer as a change in the syringyl-to-guaiacyl ratio. Hence, this work demonstrates that jute stick can be effectively delignified using biocatalyst-mediator system and utilized as biomass source, thus contributing in circular bio-economy through waste valorization.

Application of laccase immobilized rice straw biochar for anthracene degradation

The present study explores the immobilization of ligninolytic enzyme-laccase on the surface of rice straw biochar and evaluates its application for anthracene biodegradation. The rice straw biochar was acid-treated to generate carboxyl functionality on its surface, followed by detailed morphological and chemical characterization. The surface area of functionalized biochar displayed a two-fold increase compared to the untreated biochar. Laccase was immobilized on functionalized biochar, and an immobilization yield of 66% was obtained. The immobilized enzyme demonstrated operational stability up to six cycles while retaining 40% of the initial activity. Laccase immobilization was further investigated by performing adsorption and kinetic studies, which revealed the highest immobilization concentration of 500 U g^-1 at 25 °C. The adsorption followed the Langmuir isotherm model at equilibrium, and the kinetic study confirmed pseudo-second-order kinetics. The equilibrium rate constant (K₂) at 25 °C and 4 °C were 3.6 × 10^-3 g U^-1 min^-1 and 4 × 10^-3 g U^-1 min^-1 respectively for 100 U g^-1 of enzyme loading. This immobilized system was applied for anthracene degradation in the aqueous batch mode, which resulted in complete degradation of 50 mg L^-1 anthracene within 24 h of interaction exposure.