Optimization of solid-state fermentation for production of cellulase from agricultural residues

Abstract:

Agricultural residues such as rice straw, wheat bran, and sugarcane bagasse accumulate in vast quantities each harvest season and pose disposal problems when burned in the open. Converting these lignocellulosic wastes into a substrate for microbial enzyme production is one route to add value while reducing environmental harm. This research optimised solid-state fermentation (SSF) conditions for cellulase production by Aspergillus niger MTCC 2196 grown on three agricultural residues at the Federal University of Agriculture, Abeokuta, Ogun State, during August-December 2023. Wheat bran supported the highest cellulase activity (18.3 IU g⁻¹ dry substrate) at 72 h, pH 5.5, 30 °C, and 65% initial moisture content, followed by rice straw (14.6 IU g⁻¹) and sugarcane bagasse (12.1 IU g⁻¹). A one-factor-at-a-time approach established that pH 5.5, 30 °C, and a moisture level of 65% were the most favourable conditions. Supplementation with 1% yeast extract further raised cellulase yield on wheat bran to 21.7 IU g⁻¹. The findings indicate that wheat bran, an inexpensive agro-residue, can serve as an effective substrate for on-farm cellulase production applicable to bioethanol pre-treatment and animal feed processing.