The present study evaluated the surfactin production by Bacillus subtilis UFPEDA 438 using sugarcane molasses as a substrate. The effects of the cultivation conditions (temperature, agitation and aeration ratio) on the biosurfactant production and kinetic parameters were investigated. Characteristics of the biosurfactant were obtained after analyses of the emulsification index (EI) and critical micellar concentration (CMC) of the fermentation broth. The results showed that in relation to the product its formation kinetics is strongly affected by operational conditions. It was also observed that surfactin production can be partially dependent or fully independent on microbial growth. The maximum values of surfactin concentration (199.45 ± 0.13 mg/L) and productivity (8,187 mg/L.h) were obtained in the culture under cultivation time of 24 h, temperature of 36 °C, agitation of 100 rpm and aeration ratio of 0.4. Under optimal conditions, the fermentation broth achieved good emulsification capacity (EI >40%) and CMC value of 20.73 mg/L. The results revealed that Bacillus subtilis UFPEDA 438 is a good producer of biosurfactant and that sugarcane molasses is a viable substrate for the production of surfactin.
Keywords: Aeration; agro-industrial residues; bacteria; biosurfactant; submerged fermentation.