Enhanced production of 1-deoxynojirimycin in Bacillus subtilis subsp. inaquosorum by random mutagenesis and culture optimization

Abstract

1-Deoxynojirimycin (DNJ) is a potent inhibitor of α-glucosidase having antidiabetic and antiviral activities. In the present study, DNJ production by Bacillus subtilis subsp. inaquosorum KCTC 13429 (B. subtilis IWT) was confirmed and a mutant B. subtilis I.247 strain showing 50% increased DNJ production than wild-type strain after cultivation in 5% defatted soybean meal (DFS) for five days was isolated by UV random mutagenesis. The optimum culture conditions to maximize DNJ production by B. subtilis I.247 was predicted using response surface methodology to cultivate in medium containing 3.4% sorbitol and 2.4% yeast extract as carbon and nitrogen sources, respectively, at a temperature of 32°C. Under these conditions B. subtilis I.247 was able to produce 359 mg/L after five days of cultivation. Furthermore, when the B. subtilis I.247 transformant harboring a vector expressing a gabT1-yktc1-gutB1 DNJ biosynthetic gene cluster was cultured under the optimized condition, DNJ production was increased to 773 mg/L, representing a level 6.2-fold higher than that of the wild-type strain cultured in 5% DFS for five days.