Abstract: Optimization of Bacillus licheniformis M109 culture medium in this research based on the orthogonal test, carbon source, nitrogen source and carbon nitrogen ratio were determine as necessary for fermentation medium of Bacillus licheniformis M109. In order to enhance Bacillus licheniformis M109 fermentation level, growth curve of Bacillus licheniformis M109 and trend of pH, dissolved oxygen(DO) were studied. Though studying the fermentation process of growth, the optimal pH and inoculation amount were determined. The results found that DO was a key factor that limited the growth of Bacillus licheniformis M109. It was studied regulation rotate speed of stirring to improve dissolved oxygen and the fermentation density in culture medium. Another study found that Bacillus licheniformis M109 fermentation level could be improved by adding fresh medium. Through optimization of culture medium and conditions, the fermentation level of Bacillus licheniformis M109 incneased to 1.2?10¹⁰ CFU/mL from the inital 1.0?10⁹ CFU/mL and the rate of bacillus arrived to 88%.

Key words: Bacillus licheniformis; culture medium; fermentation condition; optimization