Use of onion peels as an economical substrate for microbial inulinase production under solid state fermentation

Onion (Allium cepa) is a valuable vegetable and a candidate for sustainable waste management in agri-food industry. The purpose of the current paper was to research the utilization of onion peels to an economical substrate for inulinase production by Yarrowia lipolytica ISF7 strain under solid state fermentation (SSF). SSF is preferred to obtain an effective and low-cost inulinase production. The medium designation was optimized using Taguchi design of experiment. For this purpose, Taguchi L9 orthogonal array layout was applied using the moisture content, initial pH and incubation time as the selected factors at three levels. The results showed that the minimum inulinase activity 22.7 U g-1 of dry substrate (ds) was determined using the 6th experimental setup while the highest inulinase activity 292.2 U gds-1 was measured from 5th experimental setup. The predicted value was determined as 311.6 U gds-1 which was closer to the obtained result (305.1 U gds-1). Consequently, an effective inulinase production can be achieved by Y. lipolytica ISF7 using onion peels as an economic substrate under SSF.