Effect on crude oil by thermophilic bacterium

The objective of this study is to demonstrate the basic characteristics of thermophilic strain TH-2 and evaluate the effect of strain TH-2 on different crude oils. Strain TH-2 is a non-motile, Gram-negative, oil-degrading thermophile that was isolated from a reservoir of the Shengli oil field in East China. The cells of strain TH-2 were grown at high temperatures up to 85 degreesC in the neutral to alkaline pH range. Depending on the culture conditions, the organisms occurred as single rods, or as filamentous aggregates. Strain TH-2 was grown chemoorganotrophically and produced volatile fatty acids and such surfactants as 1,2-benzenedicarboxylic acid-bis ester, dibutyl phthalate, and di-n-octyl phthalate. It could use different organic substrates (acetate, D-glucose, fructose, glycerol, maltose, pyruvate, starch, sucrose, and xylose). Laboratory studies have demonstrated that the strain affected different crude oils, converted and degraded various components and changed the physical and chemical properties of crude oils. The strain TH-2 degraded crude oil and growth of the bacterium on crude oil resulted in loss of aromatic hydrocarbons, resins, and asphaltenes. The bioconversion of crude oils leads to an enrichment in lighter hydrocarbons and an overall redistribution of these hydrocarbons. The interactions of microorganisms with crude oils are variable and depend on the microbial species and the chemical compositions of crude oils. Different interactions may influence the efficiency of processes in which single or mixed microbial species are used for the oil treatment and may also suggest possible combinations of biological and chemical technologies. (C) 2004 Elsevier B.V. All rights reserved.