Production and antibacterial activity of biosurfactant from Saccharomyces cerevisiae

A total of four types of instant dry yeast Saccharomyces cerevisiae which are Gloripan, Swan, Super Man (China) and Saf (Turkey), were obtained from the local market in Baghdad, Iraq. All the types were identified according to their morphological characteristics and screened for their ability to produce biosurfactant by oil spread method. Biosurfactant was extracted and partially purified by precipitation with ammonium sulfate at saturation ratio75%. Antibacterial activity of crude and partially purified biosurfactant was tested against twenty isolates of Pseudomonas aeruginosa and the results showed that crude biosurfactant has no activity against tested bacteria while partially purified biosurfactant was active against only ten isolates of P. aeruginosa. Also, the effect of some optimum conditions on production was studied and the results showed that mineral salt medium with olive oil as carbon source at pH 5 and incubation at 25 degrees C for three days were optimum conditions for biosurfactant production.