Molecular Profiling and Optimization of Cellulase Production by Thermotolerant Aspergillus terreus AN1

Abstract

This paper reports molecular characterization and cellulase activity profiling of thermotolerant Aspergillus strains isolated from composting soils/ degrading paper waste. A. terreus strain AN1 was found to be a good source of cellulases that showed efficient biodeinking of mixed office waste paper. The culture was optimized for production of endoglucanase, β-glucosidase, FPase and xylanase on rice straw containing solidified culture medium employing Box Behnken design of experiments to study the influence of pH, moisture content and corn steep liquor on enzyme production. A. terreus under optimized conditions produced 162, 955, 6.6, 3027 (units/g of substrate) of endoglucanase, β- glucosidase, Fpase, and xylanase corresponding to 5.7, 5.4, 2.5 and 1.1 folds higher enzyme activities when compared to those obtained under unoptimized conditions. Isoelectric focusing (IEF) profiling of the crude extract showed that A. terreus produced three endoglucanase isoforms corresponding to pI values of 3.0, 3.9 and 5.9 that were functionally distinct and showed differences in their substrate specificity. Furthermore, four isoforms of β-glucosidase and eleven multiple forms of xylanase distributed over a wide range of pI were also detected.