Abstract

Thirteen fungal isolates were obtained from potato peels and soil in Lagos State Nigeria and were tested for amylase production by starch hydrolysis test. Production of amylase was indicated by zone of clearance around the microbial growth. On the basis of the clearance, five out of the thirteen isolates with zone of clearance of diameter above 20mm were characterized, identified and selected for further studies on amylase production and activity by solid state fermentation on cassava peels. The selected fungal isolates were identified as Aspergillus niger APP13, A. niger APP11, Aspergillus oryzae IPS11, A. niger APS11 and A. niger APS21. A. niger APP13 has the highest zone of clearance and thereby produced the highest amount of amylase. The isolates were also selected for amylase activity under optimized conditions such as temperature, carbon source, nitrogen source and metal ions. The enzyme was optimally active at 50 and 60°C, and pH of 4.5. Metal ions Co²⁺ increased the enzyme activity; moreover, addition of organic nitrogen sources such as casein, meat extract and beef extract to the medium resulted in a considerable increase in the production of amylase. Soluble starch and maltose as carbon sources also significantly increased enzyme activity.

Key words: Potato peels, Aspergillus niger, amylase, solid state fermentation.