Effect of β‐mannanase domain from Trichoderma reesei on its biochemical characters and synergistic hydrolysis of sugarcane bagasse

BACKGROUND β-mannanase is a key enzyme for hydrolyzing mannan, a major composition of hemicellulose which is the second most abundant polysaccharides in nature. Different structural domains greatly affect its biochemical characters and catalytic efficiency. But the effects of linker and CBM on β-mannanase from Trichoderma reesei (Man1) have not yet been fully described. This study aimed to elucidate the influence of different domains on expression efficiency, biochemical characteristics and hemicellulosic deconstruction of Man1. RESULTS The expression efficiency was improved after truncating CBM. Activities of Man1 and Man1△CBM (lacking carbohydrate-binding module (CBM)) in the culture supernatant after 168 h induction were 34.5 and 42.9 IU mL-1, but only 0.36 IU mL-1 was detected for Man1△LCBM (lacking CBM and linker). Man1 showed higher thermostability than Man1△CBM at low temperature, but Man1△CBM had higher specificity for galactomannan (Km=2.5 mg mL-1) than Man1 (Km=4.0 mg mL-1). Both Man1 and Man1△CBM could synergistically improve the hydrolysis of cellulose, galactomannan and pretreated sugarcane bagasse with 10-30% improvement of reducing sugar yield. CONCLUSION Linker and CBM domains were vital for mannanase activity and expression efficiency; CBM affected the thermostability and adsorption ability of Man1. These results will guide the rational design and directional modification of Man to improve its catalytic efficiency.