Optimization of Inulinase Production by a Fungal Species Isolated From Rotten Garlic Samples

Introduction: Inulinases are β-fructohydrolase enzymes that catalyze the hydrolysis of inulin. Recently, this enzyme has gained much importance mainly due to its ability to produce high-density fructose syrup using inulin as a raw material. In the current study, screening of inulinase-producing microorganisms was carried out from the rhizosphere soil of the Dahlia plant and rotten garlic samples.   Materials and Methods: The inulinase activity was detected with the help of ۳,۵-dinitrosalicylic acid (DNSA) and Seliwanoff’s method, and the organism showing the highest potential was selected for further optimization studies. Results: The optimum culture conditions for inulinase production, by the test fungal culture, were observed when ۵% inoculum was added to the minimal medium (pH ۵.۵) containing ۱% inulin/ costus root powder as a carbon source and ۰.۱۵% NaNO۳/ NH۴Cl as a nitrogen source, and incubated at ۳۰°C for ۴۸h under shaker conditions (۲۰۰ rpm). Maximum enzyme activity was observed at pH level of ۵ and temperature level of ۴۵°C, with thermal stability noted between ۳۵°C-۵۵°C. The I/S value of the crude enzyme was calculated to be ۰.۴۵ indicating true inulinase activity. It showed no significant inhibition in the presence of metal ions such as Zn+۲, Mg+۲, and Fe+۳. The Ca+۲ ions showed partial inhibition whereas Cu+۲ ions showed an enhancement in the enzyme activity. Conclusions: These factors may present the test fungal culture isolated in the present study to be a potential candidate for the production of thermo-tolerant and metal resistant inulinase enzyme in order to be used for various biotechnological processes.

Keywords:

enzyme activity , Inulinase , I/S value , Optimization , Seliwanoff’s Method