The Cost-Effective Stirred Tank Reactor for Cellulase Production from Alkaline-Pretreated Agriculture Waste Biomass

Abstract

Traditional conversion of lignocellulosic biomass into bioethanol takes place in three processes which include pretreatment, enzymatic hydrolysis, and fermentation. Among them, enzymatic hydrolysis accounts for ~40% of the total cost. Therefore, commercial production of cellulolytic enzymes by using lignocellulosic biomass as a substrate may decrease the production cost. Alkaline pretreatment of sorghum biomass was carried out with different concentrations of NaOH at 121 °C for 20–60 min for the solubilization of hemicellulose and lignin in order to increase the cellulose surface area. This pretreated biomass has comparatively rich content of cellulose than raw biomass. These pretreated substrates were subjected to cellulase production using Phanerochaete chrysosporium NCIM 1106 for the optimization of enzymatic activity (FPU). Therefore, maximum cellulase activity (36.8 FPU/g) was obtained during the fermentation of 0.2 M NaOH (at 60 min)-pretreated substrate. In order to enhance the cellulase production, bioreactor studies were performed under submerged fermentation. A laboratory scale stirred tank reactor (STR) was designed which was easily operational and sustainable. As a result, enzyme activity was successfully increased up to 51.3 FPU/g. In addition to this, hydrothermal pretreatment of sorghum biomass was performed for comparison study. However, cellulase activities were relatively lower than alkaline-pretreated substrates.