Glycoside hydrolase production by Aspergillus terreus CM20 using mixture design approach for enhanced enzymatic saccharification of alkali pretreated paddy straw

Abstract

A successful lignocellulosic ethanol production process needs to address the technological impediments such as cost-competitiveness and sustainability of the process. Effective biomass utilization requires a repertoire of enzymes including various accessory enzymes. Developing an enzyme preparation with defined hydrolytic activities can circumvent the need for supplementing cellulases with accessory enzymes for enhanced hydrolysis. With this objective, mixture design approach was used in the present study to enhance glycoside hydrolase production of a fungal isolate, Aspergillus terreus CM20, by determining the proportion of different lignocellulosic components as enzyme inducers in the culture medium. A mixture of paddy straw and wheat straw (1.42:1.58) resulted in improved cellulolytic activities. The precipitated crude enzyme showed higher CMCase (365.03 18 IU g-1), FPase (161.48 IU g-1), avicelase (15.46 IU g-1), β-glucosidase (920.92 IU g-1) and xylanase (9627.79 IU g-1) activities. The potential of the crude enzyme for saccharification of alkali pretreated paddy straw was also tested. Under optimum conditions, saccharification released 25.0 g L-1 of fermentable sugars. This indicates the superiority of the crude enzyme produced with respect to its hydrolytic enzyme components.