Optimization Studies on Cellulase Production by Aspergillus niger and Aspergillus fumigatus

Abstract

Aim: In this study, two fungal species, Aspergillus niger and Aspergillus fumigatus were screened and optimized for their abilities to degrade cellulose using filter paper and Carboxymethylcellulose (CMC) as substrates. Materials and Methods:  Aspergillus niger and A. fumigatus procured from the Applied Microbiology Unit of Department of Plant Science and Biotechnology, University of Jos were screened using Whatman No. 1 filter paper and Carboxymethylcellulose as substrates in Petri plates. The fungal species abilities to produce cellulase at varying optimization parameters such as incubation periods (5 days), different incubation temperatures (25-500C), different pH(3-9) and different substrate concentration (0.25-2%) using Submerged Fermentation (SmF) were also studied. Results: The plate assay showed that the two species produced cellulases. The highest cellulolytic activity was shown by A. niger (23±3.22 mm) as it had larger zones of clearance compared to A. fumigatus (13±3.06 mm). However, the organisms grown on filter paper agar showed better hydrolysis compared to the growth on CMC agar. For the Submerged Fermentation (SmF), enzyme activity increased for the first 98 hours of incubation on filter paper recording 2.62 IU/ml for A. niger and 2.45 IU/ml for A. fumigatus after 48 h and then there was decrease in enzyme activity. For the CMC, the highest enzyme activity was observed at 48 h recording 1.76 U/ml and 1.37 IU/ml for A. niger and A. fumigatus respectively. Maximum enzyme production was observed at incubation temperature of 30 0C for A. niger and A. fumigatus recording 1.05 IU/ml and 1.10 IU/ml on filter paper. Enzyme activity was found to be highest at pH 6 with A. niger and A. fumigatus recording 2.27 IU/ml and 2.03 IU/ml respectively on CMC broth. The 2% substrate concentration gave the highest enzyme activity of 0.58IU/ml and 0.54IU/ml for A. niger and A. fumigatus respectively. The increase was linear, the higher the concentration of the substrate, the higher the enzyme activity. Conclusion: Aspergillus  niger and A. fumigatus have demonstrated potential of synthesizing hydrolytic cellulolytic enzymes and could be employed in the degradation of lignocellulosic wastes. These enzymes could find applications in different industries.