Optimization of Sugarcane Bagasse Pretreatment with Xylaria sp. Laccase for Bioethanol Production

Sugarcane bagasse was submitted to delignification using the laccase-enriched extract (specific activity of 0.45 U.mg-1) from Xylaria sp. isolated from cassava waste. The effect of temperature (21.3 to 46.7 degrees C) and treatment time (0.2 to 5.8 days) was evaluated using an experimental design on the lignin removal. The optimized condition was achieved at 21 degrees C and two days, resulting in a delignification of 20.7%. The process efficiency was enhanced using different mediators (ABTS, syringaldazine, catechin, ferulic acid, and hydrolyzed lignin), achieving 31.2% lignin removal using syringaldazine and an increase in delignification efficiency of 51.1 +/- 1.6% when adding the mediator compared to the results in its absence. Subsequently, the pretreated biomass was enzymatically hydrolyzed to get fermentable sugars. The glucose concentration achieved 33.0 g.L-1 and cellulose conversion of 43.6% after 48 h, representing an increase of 56.0% in hydrolysis conversion compared with the control experiment (no laccase treatment) and a yield of 67.3% during the production of bioethanol from hydrolysate. Furthermore, no large amounts of wastewater were generated during the enzymatic pre-treatment process, showing a promising path for developing more sustainable biofuel production technologies.