Purification and characterization of thermostable glucoamylase from Rhizopus oligosporus SK5 mutant obtained through UV radiation and chemical mutagenesis

Thermostable glucoamylase from Rhizopus oligosporus SK5 mutant was purified in a 3-step purification using Imarsil, activated charcoal and Sephadex-G-100 to achieve a 40-fold purification. The enzyme was optimally active at pH 5.0 and temperature of 80 °C. It exhibited a half-life of 60 minutes at 70 °C. Its stability was enhanced with addition of Soyabean flour or starch (3% w/w) leading to a retention of over 90% residual activity at 4 °C and 28 °C after 12 weeks of storage. SDS-PAGE analysis of purified enzyme showed two major bands with corresponding molecular weights of 36 kDa and 50 kDa. The study presents thermostable glucoamylase from Rhizopus oligosporus SK5 as a potential in the bioconversion of starch to glucose