Enhanced production and partial characterization of thermostable α-galactosidase by thermotolerant Absidia sp.WL511 in solid-state fermentation using response surface methodology

Response surface methodology was applied to optimize medium components for maximum production of a thermostable alpha-galactosidase by thermotolerant Absidia sp. WL511. First, the Plackett-Burman screening design was used to evaluate the effects of variables on enzyme production. Among these variables, MgSO4 and soybean meal were identified as having the significant effects (with confidence level (90%). Subsequently, the concentrations of MgSO4 and soybean meal were further optimized using central composite designs. The optimal parameters were determined by response surface and numerical analyses as 0.0503% (g/g) MgSO4 and 0.406% (g/g) soybean meal and allowed alpha-galactosidase production to be increased from 4.4 IU g(-1) to 117.8 IU g(-1). The subsequent verification experiments confirmed the validity of the model. The optimum pH of enzymatic activity was 7.5 and the enzyme was stable at pH values ranging from 5.0 to 9.0. The optimum temperature was 73 degrees C. The enzyme was fairly stable at temperatures up to 60 degrees C and had 87% of its full activity at 65 degrees C after 2 h of incubation.