Optimization of High-density Culture Fermentation of Bacillus natto

The liquid fermentation medium and conditions of Bacillus natto were optimized by single factor experiments and orthogonal experiments. The most suitable medium of spore forming was identified as follows: starch 20. 0 g / L,yeast extract powder 20. 0 g / L,NH 4 Cl 1. 0 g / L,K 2 HPO 4 2. 0 g / L,KH 2 PO 4 2. 0 g / L,MgSO 4 1. 0 g / L. The best fermentation condition was as follows : initiative of pH was 8. 0,culture temperature 35 ℃, and inoculation amount 0. 05( φ = 0. 05). The productivity of Bacillus natto could reach up to 2. 95 × 1014cfu / L at the scale of 20 L scale fermentor. It provides the theoretical basis for the production of high density fermentation industry.