Isolation, purification and characterization of cellulase produced by Aspergillus niger cultured on Arachis hypogaea shells

Abstract

Cellulases are enzymes that hydrolyse cellulose and related cellu-oligosaccharides derivatives. Its applications are enormous but high cost of production is the bottle-neck against the utilization of cellulase in industries. Therefore, this study investigated the isolation, purification and characterization of cellulase produced by Aspergillus niger cultured on Arachis hypogaea shells. The crude cellulase enzyme was produced by A. niger through submerged fermentation process using A. hypogaea shells as a carbon source. The optima fermentation conditions were determined by varying different parameters. The crude cellulase was purified through ammonium sulphate precipitation, dialysis and gel-filtration chromatography. The molecular weight was estimated using sodium dodecyl sulphate polyacrylamide gel electrophoresis. The effects of pH and temperature on the activity of the purified cellulase were investigated. The study revealed that the: optimal production of crude cellulase was achieved at incubation period of 120 h, pH 4, temperature 40 °C, and inoculum size of 13 × 105 CFU/ml. Cellulase was purified to 68.12-fold with a yield and specific activity of 3.87% and 484.3 U/mg respectively. The Vmax for the cellulase was 9.26 U/ml while the Km was 0.23 mg/ml. The molecular weight of the cellulase was approximately 13.5 kDa and the enzyme has higher specificity for CMC compared to other substrates. The optimum pH and temperature for the cellulase activity were 4 and 40 °C respectively. The present study has shown that A. hypogaea shells can be used as a carbon source by A. niger for the production of cellulase.

Keywords

• Biotechnology
• Biochemistry
• Molecular biology
• Proteins
• Cellulase
• Aspergillus niger