The production and properties of biosurfactants synthesized by Candida guilliermondii NRRL Y-2075
and Bacillus subtilis NRRL B-94 using soy processing waste (okara) as substrate were investigated
under different fermentation techniques. Higher oil displacement activities for the isolated
biosurfactants were achieved by using submerged fermentation technique (SMF) for both organisms.
Preliminary chemical characterization and IR spectroscopy for C. guilliermondii biosurfactant revealed
that, it is mainly a glycolipid complex, while that of B. subtilis biosurfactant was found to be a complex
mixture of lipoprotein and glycolipid. Both biosurfactants formed stable water-in-oil emulsions with
motor oil and sunflower oil, while soybean oil was only emulsified by C. guilliermondii biosurfactant.
The surface tension of water was reduced to 51 mN/m by C. guilliermondii biosurfactant at a critical
micelle dilution (CMD) of 8% concentration, while B. subtilis biosurfactant showed a minimum surface
tension of 48 mN/m at CMD value of 10% concentration. Both biosurfactants exhibited good
antimicrobial activity against the tested bacteria and yeast strains with different values of minimum
inhibitory concentrations (MIC).