Previously some fungal strains with good inulinase potential biosynthesis were screening and the most performing strain is the newly fungal strain, Rhizoctonia spp. coded I-PN4. In this study, the Plackett Burman design was used to identify the effect of process parameters upon fructofuranosidases (inulinase and invertase) production with new selected fungal strain. The agitation rate, yeast extract, buckwheat flour and K 2 HPO 4 concentration from fermentative medium composition, were determined as the most influential variables that have positive effects on fructofuranosidases biosynthesis. Temperature has a negative effect on both invertase and inulinase biosynthesis yield. In optimal established fermentative conditions, the maximum yields for extracellular inulinase was 6.2198 UI and 4.7664 UI for invertase respectively. The linear model fits well for variable screening and is globally significant, as R 2 is 88.36% for inulinase production and 84.24% for invertase production respectively.

Aims: A newly isolated strain of Rhizoctonia ssp. was used for the production of extracellular inulinase. Previously, the qualitative effects of some carbon and nitrogen sources from fermentative media and the physicochemical parameters for growth were established by Plackett-Burman analysis, and the main parameters that affect extracellular inulinase yield were identified. In this study, the quantitative effect of the carbon to nitrogen ratio in the fermentative medium and the growth temperature were studied and optimized using central composite design and response surface methodology. Methods and results: On the basis of optimization, the maximum extracellular inulinase activity was achieved when 2AE5-6AE5% buckwheat flour was used as a single carbon source and 4AE6-5AE0% yeast extract was used as nitrogen source, by submerged cultivation, after 48 h at an incubation temperature between 15 and 27AE5°C. Conclusions: Under the fermentative conditions established in this study, a maximum extracellular inulinase yield of 1AE8 UI ml )1 was achieved. Rhizoctonia ssp. strain can be used for extracellular inulinase production. Also, buckwheat flour proved to be an inexpensive and abundant substrate suitable for obtaining inulinase.Significance and impact of the study: Inulinases are versatile tools for biotechnology as they can be used for a wide range of applications, including production of bioethanol, fructose syrup and inulo-oligosaccharides, lactic acid, citric acid and butanediol. Letters in Applied Microbiology

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