Utilization of cassava fiber for cellulase and ethanol production

Abstract

Cassava fiber which obtained from digestion of cassava waste (15%wet w/v) by α-amylase and glucoamylase (Spezyme, USA) using method described by manufacturer and separated from starch solution by centrifugation was used as both carbon source for endoglucanase and b-glucosidase production by Aspergillus terreus strain 24 and A. niger strain 127, respectively, and substrate for ethanol fermentation by S. cerevisiae TISTR 5596 via simultaneous saccharification and fermentation (SSF) method. At optimized condition, A. terreus strain 24 produced endoglucanase (51.6 units/g cassava fiber, dry weight basis (DS)) and b-glucosidase (0.64 units/ g DS cassava fiber), while A. niger strain 127 produced b-glucosidase (37.2 units/ g DS cassava fiber) and endoglucanase (1.68 units/ g DS cassava fiber). The above enzymes were mixed in order to adjust endoglucanase and b-glucosidase ratio to 2:1 and it was used in the SSF experiment. Optimal conditions for ethanol production from the cassava fiber by SSF method was 40°C, 72 h of incubation and using 128.57 units of endoglucanase and 59.29 units of b-glucosidase/g DS cassava fiber. At the optimal condition, ethanol (40.19 % g/g DS of cassava fiber) was produced. Using the method described above, ethanol production from cassava waste was 25% higher than ethanol produced from only starch component of the cassava waste.