Isolation and identification of biosurfactant producing actinomycetes from soil

Abstract

Two hundred and twenty-nine soil actinomycete strains were initially screened for extracellular biosurfactant activity by a drop-collapse method in Kim's medium containing sesame oil as a sole source of carbon. Three isolates, namely S71, S72 and S177, were capable of biosurfactant production. Phenotypic and genotypic analysis strongly suggested that they were members of the genus Streptomyces. The isolates S71 and S177 were closely related to S. griseoflavus sharing 99% 16S rRNA gene similarities, whereas S72 was closely related to S. fradiae sharing only 98% 16S rRNA gene similarities suggesting that this may represent a novel species. The cell-free culture broth of the three isolates had emulsification activity and decreased surface tension. According to emulsification activity (E24) and surface tension values observed in the three isolates, Streptomyces sp. S72 was selected for biosurfactant production in larger scale. The cell-free culture broth of the isolate S72 was further extracted with chloroform:methanol (2:1) and two fractions were found positive in producing biosurfactants. To determine structure and molecular weight of the two positive fractions, the Nuclear Magnetic Resonance (NMR) spectroscopy and Mass Spectrometry (MS) will be carried out. © 2008 Academic Journals Inc.