Alkaline inulinase production by a newly isolated bacterium Marinimicrobium sp. LS–A18 and inulin hydrolysis by the enzyme

Abstract

To date, all of microbial inulinases reported showed optimal activity at pH values ranging from 3.5 to 7.0. A bacterial strain, Marinimicrobium sp. LS-A18, showing high extracellular inulinolytic activity was isolated from a marine solar saltern of the Yellow Sea in China. Maximum enzyme activity was obtained at 55°C and pH 9.0, respectively. The inulinase activity was induced by inulin, but not by the other carbon sources employed. Under the optimal medium and culture condition, the highest inulinase activity, 14.6 U/ml, was obtained after 96h of incubation at shake flask level. The optimal medium for inulinase production was MHI medium containing 4% inulin, 1% peptone and 5% NaCl, while the optimal culture condition for inulinase production were pH 7.5, temperature 37°C, agitation speed 210rpm, medium volume 40ml in 250ml shake flask, and incubation time 96h. A large amount of monosaccharides was released after inulin hydrolysis by the inulinase from strain LS-A18. This is the first report on alkaline inulinase production from microorganism.