Solid-State Fermentation of Carrot Pomace for the Production of Inulinase by Penicillium oxalicum BGPUP-4

Abstract

Inulinases are an important class of industrial enzymes which are used for the production of high-fructose syrup and fructooligosaccharides. Inulin, a polyfructan, is generally employed for the production of inulinase, which is a very expensive substrate. A number of agroindustrial residues have been used for cost-effective production of inulinases. In the present study, carrot pomace was selected as a substrate for the production of inulinase by Penicillium oxalicum BGPUP-4 in solid-state fermentation. Carrot pomace is one of the good substrates for bioprocesses, because it is rich in soluble and insoluble carbohydrates. A central composite rotatable design (CCRD) used in response surface methodology was employed for the optimal production of inulinase from carrot pomace. Using CCRD, 15 runs were practiced to optimize the range of three independent variables: moisture content (70-90 %), incubation time (4-6 days) and pH (5.0-7.0) for inulinase production. Carrot pomace supplemented with 0.5 % inulin as an inducer, 0.2 % NH4H2PO4, 0.2 % NaNO3, 0.2 % KH2PO4, 0.05 % MgSO4·7H2O and 0.001 % FeSO4·7H2O was used for the production of inulinase in solid-state fermentation at 30 °C. Inulinase production (322.10 IU per g of dry substrate) was obtained under the optimized conditions, i.e. moisture content of 90 %, incubation time 4 days and pH=7.0. The corresponding inulinase/invertase (I/S) ratio (3.38) was also high, which indicates the inulolytic nature of the enzyme. Multiple correlation coefficients R for inulinase production and I/S ratio were 0.9995 and 0.9947, respectively. The R value very close to one indicates an excellent correlation between experimental and predicted results.

Keywords

• inulinase
• carrot pomace
• Penicillium oxalicum
• solid-state fermentation
• response surface methodology