Saccharification of Leptochloa fusca (kallar grass straw) using thermostable cellulases

Abstract

Saccharifying ability of thermostable cellulases on kallar grass straw at 50 and 60°C was evaluated. Enzyme filtrate from Chaetomium thermophile saccharified 5% kallar grass straw to 69% reducing sugars (quantitatively) at 50°C. Culture filtrates from all the thermophilic fungi showed a considerable saccharification rate up to 40 h. Freeze-dried enzyme of Trichoderma reesei VTT-D-79125 (mesophile), even at higher enzyme concentration resulted in 60% reducing sugars yield (quantitatively). Glucose concentration in the hydrolysates from the fungi was in the order of C. thermophile > T. reesei > Sporotrichum thermophile > Aspergillus fumigatus > Torula thermophila > Humicola grisea > Malbranchea pulchella. At 60°C, thermostable enzymes hydrolysed kallar grass straw at a maximum rate for the initial 20 h, after which the rate essentially stopped increasing. However, at elevated temperature C. thermophile enzymes saccharified kallar grass straw up to 20 h to almost the same yield in half the time as compared to that at 50°C. The overall decline in saccharification yield (11%) of C. thermophile enzymes was significantly lower than T. reesei enzymes (34%) at 60°C.