Abstract:

A strain XDF-4 was obtained by isolation from stratum water of oil recovery in Longhupao block of Daqing oil field, and identified as Geobacillus sp. by morphological observation, physiological and biochemical test and 16SrDNA gene sequence analysis. It grows well at 45—75℃, pH 6. 5—9.0 and salt concentration 0—10%, and the optimum conditions was 65℃ and salt concentration 3%. It was found that XDF-4 could utilize crude oil as sole carbon source to synthesize biosurfactant at high temperature and salinity, which could lead to decrease in surface tension of the culture medium from 68.59 mN·m^-1 to 29.58 mN·m^-1 after 7d zymolysis. The results from thin-layer chromatography and chromogenic reaction showed that the biosurfactant produced by XDF-4 involves three main compounds: glycosides 50.26%（mass）, lipids 28. 47%（mass） and protein 15. 35%（