Abstract: A strain of acid-producing Bacillus sp., designated JLNK03, was isolated from the sediment soil from a water pool in this experiment. The strain was identified as Bacillus coagulans through colony and cell morphology observation and 16S rDNA sequencing. To increase the spore production of B. coagulans strain JLNK03,single-factor and orthogonal experiments were conducted to optimize the culture conditions and medium composition for sporulation conditions, and the effects of three sporulation-promoting factors on the sporulation were also investigated. The results showed that the optimal culture conditions for spore production of strain JLNK03 were as follows: culture medium of 12 mL in a 50 mL conical flasks, inocularatio of 3.5% (V/V), initial pH of 6.5, and incubation at 40 ℃ with shaking at 180 r/min for 50 hours. The optimal medium composition consisted of 8 g/L corn starch, 14 g/L soybean powder, 4 g/L magnesium sulfate, and 2 g/L calcium sulfate, supplemented with 2 g/L long-chain inulin as a sporulation-promoting factor. Under this conditons, the average spore count reached (1.13±; 0.02)×; 10¹⁰ CFU/mL, which was 3 to 4 orders of magnitude higher than that before optimization. It significantly increased the spore count. This method was relatively simple, and the medium components were cheap and easy to obtain, which could effectively reduce the cost and obtain high-yield spores.

Key words: Bacillus coagulans, isolation, identification, spore, spore formation factor, optimization