Microbial conversion of vegetable oils into surface-active di-, tri-, and tetrasaccharide lipids (biosurfactants) by the bacterial strain Tsukamurella spec.

Abstract

The vegetable oil utilizing bacterial strain Tsukamurella spec. (DSM 44370) growing on oleic acid rich sunflower oil was found to produce a mixture of oligosaccharide lipids. In addition to trehalose lipids (GL I) also trisaccharide (GL2) and tetrasaccharide lipids (GL 3) were detected. In submerged culture the tri- and tetrasaccharide lipids were overproduced during the stationary phase (nitrogen limitation) and excreted into the supernatant. In contrast, the trehalose lipids were synthesized growth-associated. As a result of bioreactor cultivations approximately 30g 1 -1 glycolipids were produced from 110 g 1 -1 sunflower oil. Interfacial properties of the crude product and the purified compounds were investigated. The surface tension of water was reduced to less than 30 mN m -1 and the interfacial tension water/n-hexadecane was lowered down to 5-10 mN m -1 , Moreover, the HLB values of the purified compounds were estimated to be between 8 and 10. The glycolipids show antimicrobial activities against gram-positive and gram-negative bacteria and one fungal strain.