Biodelignification of some agro-residues by Stenotrophomonas sp. CFB-09 and enhanced production of ligninolytic enzymes

Biological delignification is an environmental friendly pretreatment method for enhanced enzymatic hydrolysis of lignocellulosic biomass and fermentation processes. In an attempt to optimize delignification process which is crucial for effective biofuel production from agro-residues, this study investigated biodelignification of some agro-residues (coconut shell {CS}, coconut husk {CH}, palm kernel shell {PKS}, oil palm empty fruit bunch {OPEFB} and sawdust {SD}) by Stenotrophomonas sp. CFB-09 under submerged fermentation conditions. Initial lignin and residual lignin contents of each agro-residue were determined at the beginning and end of 216 h biodelignification period. Production of ligninolytic enzymes was monitored at 12 h intervals. Effects of nitrogen sources, temperature and pH on production of ligninolytic enzymes were determined over the biodegradation period. Remarkably, biodelignification of the agro-residues was in the range of 41-55%. Laccase had highest yield (31 U/mg) on CH, PKS and OPEFB. Lignin peroxidase production (381 U/mg) was maximum on OPEFB, and manganese peroxidase had highest yield (53 U/mg) on PKS. Surprisingly, there was appreciable production of ligninolytic enzymes at higher temperatures of biodegradation with 40-55% yield at 80 °C. Maximum enzyme production was achieved at 40 °C, pH 8.0 with ammonium nitrate as nitrogen source. Results provide deeper insights into biodelignification of agro-residues and demonstrate potential of Stenotrophomonas sp. CFB-09 for use in biodegradation of agro-residues, especially in pretreatment of lignocellulosic biomasses for production of biofuel and other value-added products.