Hydrolysis of Tuber Peels and Sorghum Chaff by Cellulolytic Culture Filtrates of Aspergillus Niger AC4 Isolated from Agricultural Waste Dumpsites

Abstract

Six  of the twenty strains of Aspergillus niger isolated from tuber peels and sorghum chaff collected from twenty two agricultural waste dumpsites show strong capacity for producing  cellulase  enzyme using PDA plate supplemented with 2% (w/v) carboxylmethylcellulase incubated at room temperature. Cellulase production was detected by staining the plates with 2% congo red solution and then measuring the zone of clearance around the fungal colonies on the plates. Aspergillus niger AC4 produced the largest zone of clearance (3.63cm) on the PDA congo red stained plate and also gave the highest cellulase activity (240U/ml) on hydrolysis hence it was selected for further studies. Culture filtrates of the Aspergillus nigerAC4 had optima temperature, concentration and pH at 35^oC, 4% and 5.0 respectively. Culture filtrates of Aspergillus nigerAC4 was also used to hydrolyze yam peel, cocoyam peel, sweet potato peel, sorghum chaff and carboxylmethylcellulase (CMC) in comparison. Hydrolysis was significantly dependent on cellulose source and length of incubation (P<0.05). cellulose activities differ significantly in the cellulose sources ranging from 240U/ml in cassava peel to 54U/ml in sorghum chaff. It is concluded that cassava peel might be a better substrate for the production of cellulase by Aspergillus niger than commercial  carboxymethlcellulase (CMC).

Key words: Tuber Peels, Sorghum Chaff,  cellulolytic filtrate and hydrolysis.