Enzymatic hydrolysis of maize straw polysaccharides for the production of reducing sugars

Enzymatic hydrolysis of maize straw polysaccharides was investigated for the production of reducing sugars. After maize straw was pretreated with 2% sodium hydroxide at 80 °C for 1 h to delignify, the cellulosic residues were hydrolyzed by cellulase from Trichoderma reesei ZU-02 and the hydrolysis yield at 48 h was 65.9%. A certain amount of cellobiose was accumulated in the hydrolysate due to low cellobiase activity in T. reesei cellulase. Supplementing cellobiase from Aspergillus niger ZU-07 greatly reduced the inhibitory effect caused by cellobiose, and the hydrolysis yield at 48 h was improved to 81.2% with cellobiase activity enhanced to 10 CBU/g substrate. The addition of 5 g/l Tween-80 improved the enzymatic hydrolysis by increasing the hydrolysis yield of 7.5%. Fed-batch hydrolysis was started with a batch hydrolysis containing 80 g/l substrate, with cellulosic residues added at 6 and 12 h to get a final substrate concentration of 110 g/l. After 72 h of hydrolysis, the reducing sugars concentration reached 89.5 g/l with a hydrolysis yield of 83.3%. The hydrolysate from fed-batch hydrolysis contained 56.7 g/l glucose, 23.6 g/l xylose, and 5.7 g/l arabinose, which is suitable for subsequent fermentation process.