Production, Characterization and Antimicrobial Activity of a Bioemulsifier Produced by Acinetobacter baumanii AC5 Utilizing Edible Oils

Biosurfactant or Bioemulsifier amphiphilic compounds are; produced by microorganisms as primary or secondary metabolites. The unique properties of biosurfactants mean that they have the potential to supplement, or even replace, chemical surfactants used in food, in the cosmetics and pharmaceutical industries; and in the environment. In the present study ten Acinetobacter sp. isolated from different sources were tested for their capability to produce bioemulsifiers in mineral salt medium with addition of 1% (v/v) edible oil as the sole source of carbon. Out of the ten Acinetobacter isolates tested, five showed lipase activity and produced bioemulsifiers exhibiting an emulsification index (EI24%) of 40 – 78%. The results revealed that the isolate Acinetobacter baumanii AC5, a gram negative, oxidase negative, aerobic and a diplococcoid rod bacterium was the best bioemulsifier producer. Optimization studies indicated that bioemulsifier production was associated with bacterial growth, and that the presence of inducer edible oils in the medium also enhanced bioemulsifier production. On the other hand, bioemulsifier production decreased when hydrocarbon (gasoline and diesel oil) were used. Crude bioemulsifier was recovered from the culture supernatant by a solvent system of chloroform: methanol (2:1 v/v), with the extraction producing 5.05 g/l of crude bioemulsifier. Partial purification and chemical analysis of the bioemulsifier revealed that it is a lipoglycan in nature with lipid content of 63%, carbohydrate 35% and a minor fraction of protein 2%. The crude bioemulsifier; showed strong antimicrobial and antifungal activity against tested pathogenic microorganisms.