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

Abstract

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.