Production of ligninolytic enzymes with wheat bran, sugarcane bagasse and its hydrolysate

Abstract

Lignin is considered the second most naturally occurring amplest biopolymer after cellulose in nature, accounting for approximately 25% of lignocellulosic biomass. Nowadays, lignin degradation has attracted attention in research with the aim of reducing the heterogeneous structural complexity of lignin for efficient utilization of lignocellulosic biomass as a naturally renewable resource for viable energy and also for lignin valorization to some valuable product. Various approaches have been used to better understand the lignin complex polymeric structure and its recalcitrant nature to develop economical, simple, and eco-friendly methods for lignin degradation. Enzymes from various specific strains of bacteria and fungi (mainly white rot) have been identified by researchers known as ligninolytic enzymes that can efficiently metabolize lignin and convert it from waste by-product to some fine valuable chemicals. Solid-state fermentation (SSF) is known as one of the efficient methods for producing ligninolytic enzymes as well as other industrially important enzymes. Most companies produce enzymes using Submerged Fermentation(SmF), but from the last decade, the trend of enzyme production using SSF has been increasing as it promises many advantages over traditionally employed SmF, such as higher yield, high productivity, and less effluent generation. Currently, various ligninolytic enzymes produced by bacteria and fungi in SSF are prone to deactivation at elevated environmental conditions. Various delignification processes involving agricultural residues demand high temperature and elevated pH. In this thesis, the production of lignin peroxidase enzyme was carried out by halophilic archaea GSL-12 under SSF, with wheat bran as a solid substrate to know its practical application in degrading lignin. The metabolic activity of culture during SSF was monitored by carbon dioxide evolution using a gas analyzer. Further studies on utilizing crude enzymes for the treatment of lignin-rich biomass will explore the potential application.