中国生物工程杂志

Objective: To investigate the synergistic regulation of carbon and nitrogen sources on the cell growth and spore generation of Bacillus licheniformis BF-002, so as to increase the number of living cells and spores in fermentation broth. Methods: Under the scale of 5 L fermentor, the effects of nitrogen source concentration and carbon source concentration on cell growth and spore formation were investigated, and the method of starting spore formation and promoting the continuous and efficient transformation of vegetative cells into spores by adjusting carbon source concentration was established. Finally, the carbon source/nitrogen source synergistic feeding control strategy was established to improve the production of living cells and spores at the end of fermentation. The results showed that spore generation could be initiated when the concentration of carbon source decreased to the critical level (about 0.5 g/L) or when the concentration of carbon source decreased to the critical level (about 2.0 g/L). The concentrations of glucose and amino nitrogen were controlled at 10 g/L and 1.5 g/L, respectively before 24 h, and maintained at 2 g/L and 0.5 g/L after 24 h for 48 h. The number of living cells and spores reached 2.88×10¹⁰ CFU/mL and 2.56×10¹⁰ CFU/mL, respectively. Compared with the optimal batch with glucose concentration controlled alone, the number of spores increased 2.91 times. Conclusion: When the concentration of carbon source and nitrogen source in logarithmic growth period is controlled at an appropriate level, a higher amount of living cells can be obtained. Subsequently, by reducing the concentration of carbon source and nitrogen source and keeping them at their respective critical levels, we can promote the continuous and efficient transformation of vegetative cells into spores.