Laccase-mediated silver nanoparticles as a nano-biocatalytic pretreatment platform for enhanced saccharification and bioethanol production from sugarcane bagasse.

Lignocellulosic biomass represents a promising renewable feedstock for second-generation (2G) bioethanol production; however, the recalcitrant nature of lignin remains a major barrier to efficient biomass conversion. The present study investigated the application of for enhanced lignin-targeted pretreatment followed by enzymatic hydrolysis and bioethanol production Among the fungal isolates screened, isolate A19 exhibited the highest laccase-producing ability and was identified as Aspergillus fumigatus. Optimization studies revealed a maximum laccase activity of 0.0885 IU at pH 5.5, 30 °C, and 7 days of incubation using guaiacol as substrate. Crude laccase was successfully employed for the green synthesis of Lac-AgNPs, which were characterized by UV-Visible spectroscopy, FTIR, DLS, zeta potential analysis, and TEM, confirming the formation of stable spherical nanoparticles. Enzymatic hydrolysis of pretreated biomass yielded maximum total and reducing sugar concentrations, reducing lignin content and enhancing cellulose accessibility. Structural characterization further demonstrated disruption of the lignocellulosic matrix and increased biomass porosity. Subsequent cellulase-mediated hydrolysis of the pretreated biomass yielded maximum total and reducing sugar concentrations of 191.29 mg/mL and 74.22 mg/mL, respectively. Subsequent fermentation using Saccharomyces cerevisiae resulted in a maximum ethanol concentration of approximately 8.0 mg/mL, representing a 12-15% increase in ethanol yield compared with crude laccase-pretreated biomass. The enhanced saccharification and bioethanol production achieved through Lac-AgNP-assisted pretreatment demonstrate the potential of nano-biocatalyst-based strategies for sustainable biomass valorization and economically viable 2G bioethanol production.