Optimization of laccase production and its application in delignification of biomass

Purpose Current research focuses on the biological delignificationof biomass by microbial laccase which is anenvironmentally friendly process.Methods Various statistical approaches were designed foroptimization of laccase production like Plackett–Burmandesign as well as response surface methodology (RSM). Alaccase mediator system was designed for the delignificationof saw dust which was molecularly characterized byhigh-performance liquid chromatography (HPLC), Fouriertransformation infrared spectroscopy (FTIR) and scanningelectron microscopy (SEM).Results The present study reveals wheat bran is a potentialsubstrate for the production of laccase (63 U/g and 9.6 mg/g protein) under solid-state fermentation by Trichodermaharzianum strain HZN10. Statistical optimization by RSMusing central composite design (CCD) revealed that wheatbran contributed maximally to the overall laccase productionfollowed by yeast extract. Laccase production underoptimized conditions yielded 510 U/g with 8.09-foldincrease. HPLC peaks representing 4-hydroxy-3-methoxybenzoic(vanillic) acid and 4-hydroxy-3,5-dimethoxybenzoic(syringic) acid showed drastic reduction in laccasetreatedsaw dust sample indicating the elimination of toxicinhibitors, thereby signifying the detoxification of sample.The laccase-treated saw dust showed 1.6-fold increase inreducing sugars after enzymatic (cellulase) hydrolysis. TheFTIR analysis revealed the structural alterations occurringduring the delignification process. SEM of biologicallytreated saw dust revealed the morphological alterationsduring the delignification process targeting the fiber cellwalls rich in lignin.Conclusion The delignification of saw dust was effectiveby laccase mediator system and was evidenced by HPLC,FTIR and SEM analysis. Hence, laccase can be a powerfultool in biomass to biofuel conversions.