Synergistic effect of syringic acid and gallic acid supplements in fungal pretreatment of sweet sorghum bagasse for improved lignin degradation and enzymatic saccharification

Sweet Sorghum Bagasse (SSB) has potential for uses in production of ligninocellulosic biofuel and other fermentation products due to higher biomass yield. Pretreatment of SSB by Coriolus versicolor with synergistic syringic acid-gallic acid supplements for enhanced ligninolytic enzyme production, lignin degradation, selectivity value (SV) and enzymatic saccharification have been studied. C. versicolor was selected due to its high ligninolytic and low cellulolytic enzyme activities in SSF with 19.3 +/- 0.8% ww(-1) of lignin degradation in 20 days and SV 0.65. Supplement gallic acid increased the production of MnP; while syringic acid increased the production of LiP, MO and laccase with enhanced lignin degradation and SV. Combined supplements increased the production of multiple ligninolytic enzymes further than the effect of individual supplements due to synergistic interactions. Activities of laccase, LiP, MnP, PPO and AAO increased by 9.1, 14.6, 2.6, 1.9 and 2.2 folds respectively, which resulted in highest lignin degradation (1.56 times) and SV (3.87 times). Enzymatic hydrolysis of SSB pretreated with combined supplements yielded higher fermentable sugar (similar to 2.18 times). Combined supplements could be used for improvement in pretreatment by SSF. XRD, SEM, FFIR and TGA/DTG analysis of SSB confirmed the results. (C) 2017 Elsevier Ltd. All rights reserved.