Abstract

The main objective of this study was to produce glucoamylase under optimum conditions and to study the effect of chemical mutagenesis on Aspergillus niger for the production of glucoamylase. The maximum activity of glucoamylase for mutant A. niger (3.185 ± 0.020 IU/ml/min) and wild A. niger (2.085 ± 0.021 IU/ml/min) was recorded in the culture filtration after 96 h of solid state fermentation of growth medium with 70% moisture level and in the presence of 0.3% yeast extract, 0.4% peptone and 4 ml Tween-80 at pH 4.8. The maximum fraction value after gel filtration for wild A. niger and mutant A. niger was 2.850 and 2.980 IU/ml/min, respectively. Purification through the sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS PAGE) revealed the indication of glucoamylase purification from A. niger. The high value of K_m shows that substrate had great affinity for glucoamylase. Glucoamylase enzyme had many useful applications in food processing industry and fermentation biotechnology.

Key words: Aspergillus niger, glucoamylase, ethidium bromide, fermentation, wheat bran.