The influence of vegetable oils on biosurfactant production by Serratia marcescens.

The production of biosurfactant, a surface-active compound, by two Serratia marcescensstrains was tested on minimal culture medium supplemented with vegetable oils, considering that it is well known that these compounds stimulate biosurfactant production. The vegetable oils tested included soybean, olive, castor, sunflower, and coconut fat. The results showed a decrease in surface tension of the culture medium without oil from 64.54 to 29.57, with a critical micelle dilution (CMD(-1)) and CMD(-2) of 41.77 and 68.92 mN/m, respectively. Sunflower oil gave the best results (29.75 mN/m) with a CMD(-1) and CMD-2 of 36.69 and 51.41 mN/m, respectively. Sunflower oil contains about 60% of linoleic acid. The addition of linoleic acid decreased the surface tension from 53.70 to 28.39, with a CMD(-1) of 29.72 and CMD(-2) of 37.97, suggesting that this fatty acid stimulates the biosurfactant production by the LB006 strain. In addition, the crude precipitate surfactant reduced the surface tension of water from 72.00 to 28.70 mN/m. These results suggest that the sunflower oil's linoleic acid was responsible for the increase in biosurfactant production by the LB006 strain.