Statistical screening of factors affecting glucoamylase production by a thermotolerant Rhizopus microsporus TISTR 3518 using Plackett-Burman design

Glucoamylase is a key enzyme used in food processing as well as in commercial production of glucose from starch. The use of thermotolerant strain of Rhizopus microsporus TISTR 3518 offers the advantages of cooling-costs reduction during fermentation and high thermostable enzyme production. The effect of various carbon and nitrogen sources on glucoamylase production was evaluated. It was found that α-amylase treated liquefied cassava starch and CH3COONH4 gave the highest enzyme activity. The influence of various medium components and culture parameters were investigated using Plackett-Burman. It was shown that CH3COONH4, FeSO4.7H2O, ZnSO4.7H2O, CaCl2, temperature and pH are significant factors affecting the glucoamylase production. The medium with the initial pH of 6.5 which consisted of α-amylase treated liquefied cassava starch, 10 gl-1; CH3COONH4, 5gl-1; K2HPO4, 0.5 gl-1; KCl, 1.5 gl-1; MgSO4.7H2O, 0.5 gl-1; FeSO4.7H2O, 0.06 gl-1; ZnSO4.7H2O, 0.035 gl-1; CaCl2, 0.05 gl-1 and C6H8O7.H2O, 5.6 gl-1 yielded the highest enzyme production (948 U ml-1) after cultivation at 40°C for 48 h.Key words: Rhizopus microsporus, glucoamylase, Plackett-Burman design