Analysis of Biosurfactant Production by a New Thermophilic and Halotolerant Bacterium, Geobacillus sp. QT (Pages: 20-28)

Wenjie Xia1,2, Hao Dong3, Li Yu2, Yongqiang Bi2 and Weichu Yu4

1Power Environmental Energy Research Institute, California 91722, USA; 2Institute of Porous Flow & Fluid Mechanics, Chinese Academy of Sciences, Langfang 065007, P.R. China; 3State Key Laboratory of Heavy Oil Processing, China University of Petroleum, Beijing 102249, P.R. China and 4College of Chemistry and Environmental Engineering, Yangtze University, P.R. China


Abstract: Geobacillus sp. QT was isolated from the brines of oil reservoir in Daqing oilfield, China, and could produce biosurfactants with different hydrophobic or hydrophilic hydrocarbons. As a result of biosurfactant production, the surface tension of the culture was reduced from 71.59 mN/m to 25.9 mN/m. Two types of biosurfactants of this strain by using different carbon source were obtained. GPC analysis showed that the number-average molecular weightsof the biosurfactants were 466-652 Da for type I and 269,485-406,158 Da for type II, with PDI values of 1.079-1.161 and 1.155-1.22, respectively. Chemical composition studies exhibited that two types of biosurfactant consisted of carbohydrates, lipids and proteins with different composition ratio. Emulsification assays approved the effectiveness of biosurfactants over a wide range of temperature, pH, salinity and with different metal ions. Sand packs tests indicated the potential value of the biosurfactants of this strain in enhanced oil recovery.

Keywords: Geobacillus sp., Biosurfactants, Surface activity, Emulsifying activity, Oil recovery.