Abstract: In order to obtain the fermentation process of a strain of Bacillus laterosporus NBF-129, the culture medium and conditions were optimized by single factor experiment and orthogonal test, using the number of viable spores in the fermentation broth as an index. The optimal fermentation medium were（%）: corn starch 2.0, silkworm pupa meal 2.5, yeast extract 1.0, corn steep liqour 1.0. The optimal fermentation conditions were: initial pH 7.5, culturing temperature 30 ℃, rotation speed 220 r/min. After optimization, the number of viable spores in the fermentation broth reached 4.12×10⁹ CFU/mL, which was 79.1% higher than 2.30×10⁹ CFU/mL before optimization. Under the optimized medium and optimal culturing conditions, a 30-liter tank fermentation test was conducted. The incubation time was 35 hours, The number of viable spores in the fermentation broth reached 3.96×10⁹ CFU/mL. After being concentrated and freeze-dried, the number of raw powder spores was 6.70×10¹⁰ CFU/g.

Key words: Bacillus laterosporus, fermentation, culture medium optimization, orthogonal test