Hydrolysis of organic acid pretreated rice husk using cellulase obtained from Pichia kudriavzevii strain ITD-1MA-90

Rice husk is an abundant and neglected agricultural waste, constituting a serious environmental problem in Nigeria. Rice husk can be harnessed for glucose production, a good way of converting waste to wealth. Due to amorphous polysaccharide chains in hemicellulose, moderate organic acid pretreatment of rice husk improves the quantity of reducing sugar produced after enzymatic saccharification. Cellulase-producing fungi were isolated from moistened rice husk, which was exposed to microbial growth. The pure isolate was characterized using 18S-rDNA sequencing technology. Pichia kudriavzevii strain ITD-1MA-90 cellulase was purified 1.9 fold with a specific activity and yield of 17.36 U/mg, and 42.9%, respectively, with a molecular weight of 59kDa using Sephadex G-200. The temperature and pH optima were 50 °C and 5.5. The Michaelis constant (K M ) and maximum velocity (V max ) got from the double reciprocal plots were 0.1 mg/ml and 5000 U, respectively. Cellulase activity was improved by Co 2+ and Fe 2+ . The rice husk was pretreated with succinic acid, tartaric acid, citric acid, and maleic acid (1%) at 100°C for 120 min. The hydrolysis of the pretreated rice husk was done at 37 °C for 3 days. The studies showed that rice husk pretreated with citric acid showed a significant (p<0.05) increase in glucose yield, followed by succinic acid and tartaric acid, compared to the untreated. This organic acid hydrothermal pretreatment approach provides a new drive for rice husk transformation into value-added products such as glucose using the locally sourced Pichia kudriavzevii strain ITD-1MA-90, providing insights into the development of more cost-effective and efficient cellulase production processes.