A comparative study on alkaline lipase production by a newly isolated Aspergillus fumigatus MTCC 9657 in submerged and solid-state fermentation using economically and industrially feasible substrate

Abstract

A comparative study of solid-state fermentation (SSF) and submerged fermentation (SmF) for the production of alkaline lipase from a new isolate, Aspergillus fumigatus MTCC 9657, using defatted rice bran (DFRB) as a substrate was studied. Different process parameters, such as incubation period, initial pH and incubation temperature, were optimised to achieve the maximum yield of the alkaline lipase. Maximum enzyme production (8.13 U/mL) was obtained by day 7 of incubation in SSF compared to day 4 in SmF at an optimum pH of 8.5 and ambient temperature of 30 °C. Lipase produced by SSF was stable over a period of 15 days, whereas lipase production in SmF decreased by day 5. Lipase production in SSF with DFRB using sterile water as a moisture source exhibited more activity (577.5 U/70 mL) than that supplemented with mineral medium. Compared to the cost of culture medium, the solid-state substrate DFRB is inexpensive, and therefore this process is industrially and economically feasible. These results confirm the interesting potential of SSF in DFRB without any additional nutritional supplement.