Surfactin, a lipopeptide biosurfactant produced by Bacillus strains, is one of the most surface-active biosurfactants, which has potential to enhance oil recovery or environmental remediation [1].However, low yield and high production costs limit its use in these high-volume applications [2-3].In this paper, Bacillus subtilis BS-37 was immobilized on a piece of cotton towel in the 5 L stirred tank fermenter, the fill-and-draw process and foam fractionation were used for repeated batch fermentation.The culture pH is known to have significant impact on surfactin production with Bacillus subtilis strains [4].After a bio-reactor fermentation condition optimize, we developed a two-stage pH control operation for surfactin fermentation with 2 L of the medium: glycerol (24 g/L), NH4NO3 (2.5 g/L), KH2PO4· 3H2O (1 g/L), MgSO4·7H2O (0.2 g/L), FeSO4·7H2O (0.02 g/L), and incubated at 37 ℃, 300 rpm, aeration rate 1 VVM (air volume/culture volume/minute).For repeated batch fermentation (24 h), the pH value was 5.0 for the biomass accumulation in the previous 6 h;and then the pH value was adjusted to 7.5 for surfactin production.After 24 h fermentation, the first batch of fermentation was finished.The residual fermentation broth was drawn out from the bioreactor and 2 L of unsterile glycerol medium was filled in the bioreactor for continuous fermentation.The immobilized Bacillus subtilis BS-37 cells could be efficiently reused for 7 cycles, producing surfactin7887.3 mg in total.The repeated batch fermentation, low-cost foam fractionation, reusable immobilized cells, and energy-efficient open (unsterile) fermentation could greatly promote the development of industrial production of surfactin.