Response surface optimization of endoinulinase production from a cost effective substrate by Bacillus safensis AS-08 for hydrolysis of inulin

Endoinulinase (EC 3.2.1.7) hydrolyzes inulin to produce fructo-oligosaccharides of varying degree of polymerization which are potential prebiotics and widely used in the food and pharmaceutical industries. Response surface methodology has been applied to optimize the endoinulinase production from a low cost substrate by Bacillus safensis AS-08 at shake-flask level. Raw inulin extracted from Dahlia tubers was used as a carbon source as well as an inducer. Three central composite rotatable design (CCRD) parameters with varying concentrations were explored to find the most suitable combination of media ingredients for optimal production of endoinulinase and biomass yield. The variables optimized were inulin (0.5-1.5%, w/v), yeast extract (0.5-1.5%, w/v), KH2PO4 (0.03-0.07%, w/v), whereas, pH (7.0±0.2) and temperature (37 °C) were kept constant during shake-flask fermentations. Optimal values obtained by RSM were inulin (1.0%), yeast extract (1.0%) and KH2PO4 (0.05%). Using optimal concentrations of media constituents, endoinulinase production (28.67 IU/mL) and biomass yield (0.162 OD600/15) obtained were in excellence correlation with the predicted values. Endoinulinase production from a simple and cost effective medium using raw Dahlia inulin was comparable with pure inulin. Hydrolysis of inulin by crude enzyme extract at 50 °C shown a mixture of fructo-oligosaccharides.