Effect of β-Mannanase and β-Mannosidase Supplementation on the Total Hydrolysis of Softwood Polysaccharides by the Talaromyces cellulolyticus Cellulase System.

Abstract

Softwoods are promising lignocellulosic feedstock that provide numerous fermentable sugars via the hydrolysis of the components of cellulose and mannan-type hemicellulose such as galactoglucomannan (GGM). However, fungal cellulase systems are insufficient for the hydrolysis of softwood GGM due to the relatively low levels of mannan-degrading activities. To compensate for the deficient activities in the cellulase system, mannan-degrading enzymes were added to a cellulase preparation from Talaromyces cellulolyticus and the hydrolysis of a ball-milling-treated Douglas fir (BM-DF) was evaluated. The addition of a commercial enzyme derived from Aspergillus niger with high β-mannanase and β-mannosidase activities resulted in approximately 80 % mannose yield from BM-DF for a small protein loading amount (i.e., 1.4 mg/g substrate). Supplementation of β-mannanase and β-mannosidase purified from the commercial enzyme revealed that both enzymes were essential to improve the hydrolysis of BM-DF GGM by T. cellulolyticus cellulase. T. cellulolyticus produced inducible mannan-degrading enzymes using glucomannan as a carbon source. Supplementation of this enzyme preparation increased mannose yield from BM-DF to approximately 70 %. These results suggest that the enhancement of T. cellulolyticus β-mannosidase and β-mannanase productivity will be effective for the construction of cellulase system suitable for BM-DF hydrolysis.