Abstract: A 10L jar fermentation technology for production of L-lactic acid from sweet potato starch incubated with a mutant of Rhizopus oryzae AS 3.819 was developed. The optimal culture conditions were as follows: 10L jar contained 4L liquid culture medium with rotational speed from 400 to 650r/min, aeration rate from 0.5 to 0.6L/(L·min), dissolved oxygen (DO) above 88%, fermentation temperature 32℃, pH from 5.0 to 5.5 and the dose of defoamer 0.1%. Results indicated that the average yield of L-lactic acid, the conversion rate of crude starch to L-lactic acid and top biomass fermentation time were 99.54g/L, 77%, 7.2g/L and 70h, respectively.

Key words: Rhizopus oryzae, L-lactic acid, sweet potato starch, DO