Abstract: Bacillus methylotrophicus BMF 04 is an excellent antibacterial strain with strong antagonism against a variety of plant pathogenic fungi isolated and purified from the Lianyungang Sea. To further develop the application of this strain,, using the total number of bacteria and budding cell rate as indicators, the solid-state fermentation medium formulation and fermentation conditions were optimized by designing single-factor and response surface tests, and the effect of the fermentate on the growth of cucumber seedlings was determined by indoor potting experiments. The optimized solid-state fermentation medium formulation of BMF 04 strain was 92.5% soybean meal, 6.7% bran, 0.6% ammonium nitrate, 0.2% sodium chloride. The optimal fermentation conditions were pH 7, temperature 32℃, inoculation amount 15% (concentration 10⁸ cells/mL), feed-water ratio 1:1 and culture time 68 h. After optimization, the total bacteria amount could reach 6.61×10¹⁰ cells/g, and the budding cell rate was 90.7%. When the fermentation was mixed with soil at 1:250 mass ratios, it significantly improved the height, stem thickness, fresh weight and number of root whiskers of cucumber seedlings, indicating the fermentation had an obvious effect on the growth of cucumber seedlings.

Key words: Bacillus methylotrophicus, solid state fermentation, fermentation conditions, cucumber, growth promotion