Characterization of cellulase from Aspergillus tubingensis NKBP-55 for generation of fermentable sugars from agricultural residues

The aim of this work was to characterize cellulase from Aspergillus tubingensis NKBP-55 for generation of fermentable sugars from agricultural residues. The strain produced high titres of cellulase (750 U/gds) on copra meal in solid state fermentation (SSF). The enzyme preparation also showed hemicellulolytic activities (U/gds) viz. endo-mannanase (1023), endo-xylanase (167), beta-glucosidase (72) and alpha-galactosidase (54). Zymography revealed presence of six cellulases, six mannanases and one beta-glucosidase. It effectively degraded sugarcane bagasse (SCB) and rice straw (RS) releasing xylose, glucose and cellobiose. One cellulase (Cat 1, Mr similar to 65 kDa) was purified and characterized. It retained more than 50% activity at 70 degrees C after 150 mins and its activity was enhanced in the presence of Mn2+ ions (130%) and beta-mercaptoethanol (140%). FTIR and C-13 CP/MAS NMR analysis of the enzyme treated SCB and RS revealed degradation of cellulose and hemicellulose, while H-1 and C-13 liquid state NMR experiments confirmed release of glucose.