Isolation of Biosurfactant-producing Yeasts from oil-Contaminated Soil

Abstract

Biosurfactants are compounds on microbial cell surfaces or excreted extracellulary, which contain hydrophilic and hydrophobic portions that capable to decrease surface and interfacial tention. They have been recognized as important microbial products with wide application in a number of industries and processes. This research was oriented to the production using endogenous yeasts isolated from oil-contaminated soil. Strains were cultivated on yeast selective medium and the positive ones were then screened in a basal medium supplemented with palm oil olein, From 65 isolates obtained, base on their capability to reduce surface tention, nine isolates were found to be the most productive. Four isolates were originated from meneral oil-contaminated soil were Candida parapsilosis, Torulopsis etchellsii, Torulopsis sp 1, and Candida guilliermendi, whereas five isolated from palm oil-contaminated soil were Torulopsis sp2, Candida sp, Torulopsis sphaerica, Rhodotorula sp, and Candida tropicalis. In shake flask cultures, with a 10% glucose-palm oil medium, Rhidotorula sp., Candida parapsilopsis and Torulopsis etchellsii, could yield biosurfactant of 31.54 g/l, 13.71 g/l and 11. 50 g/l respectively. The results were faund to be more higher than that produced by a reference strain, i.e. Candida bombicola JCM 9596. Preliminary test suggests that the biosurfactant is composed mainly by glycolopids.