Abstract

Glucoamylase is an enzyme that hydrolyses 1,4α and 1,6β-glucosidic linkages in polysaccharides yielding glucose. Aspergillus niger strains 1, 2 and 3 were locally isolated from cassava peel dumpsite for the production of glucoamylase enzyme. A. niger strains 1, 2 and 3 were screened for their hyper producing ability on potato dextrose agar using plate assay method fortified with starch agar, and showed zone of clearance of 17.0, 23.0 and 8.0 mm, respectively. The glucoamylase activity for A. niger strains 1 and 2 were 13 000.0 and 11 740.0, respectively. These values were however higher than the activity as obtained from the commercial enzyme with 2 500.0. Investigations on the protein (mg/ml), and specific activity (units/mg) on glucoamylase produced by A. niger strains 1 and 2 was 24.20, 537.19, 23.13 and 507.57, respectively. Fractionation of the enzyme ammonium sulphate (% w/v) using 60, 80 and 100% showed that the enzyme activities were 33 179.86, 47 985.86 and 19 167.65 units/ml, respectively. Protein concentrations were 16.29, 16.29 and 21.55 units/mg, respectively, while specific activities were 2 036.82, 2 945.725 and 889.45 units/mg, respectively. The production, packaging, and commercialization of glucoamylase in Nigeria will save a lot of foreign exchange earnings, and boost the economy of Nigeria.

Key words: Glucoamylase, specific activity, Aspergillus niger, fractionation, cassava peel.