Production of cellulases from Humicola fuscoatra MTCC 1409: Role of enzymes in paddy straw digestion

Cellulases were produced from fungus Humicola fuscoatra MTCC 1409 by solid state fermentation under different cultural conditions viz. pH, incubation temperature, inoculum size and days of incubation in order to optimize the conditions for maximum enzyme production. The potential of cellulase pretreatment to increase the digestibility of paddy straw was also ascertained. Maximum enzyme production was achieved at pH 6.0 of Mandel media and at temperature 45°C. Inoculum size of 1×107 spores/ml was found to be optimum for maximum enzyme production. Enzyme production increased with the increase in days of incubation from 2 to 6 days and then declined thereafter. Cellulase units at the concentration of 1, 1.5 and 2 µmole/g were exogenously added to paddy straw and change in chemical composition of paddy straw was determined after 18, 24, 30 and 36 h of treatment. With increase in enzyme concentration and incubation period, the content of neutral detergent fibre (NDF), acid detergent fibre (ADF), cellulose and hemicellulose reduced gradually with simultaneous increase in lignin and silica content. The concentrations of NDF, ADF, cellulose and hemicellulose decreased by 9.2, 5.9, 10.8 and 23.4% respectively, however lignin and silica content increased by 9.7 and 6.4% respectively as compared to control (with no cellulase added) at 2 µmole enzyme concentration after 36 h of pretreatment. These results show that the enzyme produced from cellulolytic fungus H. fuscoatra is capable of increasing paddy straw digestibility and thus enhancing the utilization of paddy straw for different purposes.