Screening and Evaluation of Biosurfactant-Producing Strains Isolated from Oilfield Wastewater
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IGINAL ARTICLE
Screening and Evaluation of Biosurfactant-Producing Strains Isolated from Oilfield Wastewater Jianghong Liu • Yitong Chen • Ruidan Xu Yunpeng Jia
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Received: 30 January 2013 / Accepted: 13 February 2013 / Published online: 24 February 2013 Ó Association of Microbiologists of India 2013
Abstract The six biosurfactant-producing strains, isolated from oilfield wastewater in Daqing oilfield, were screened. The production of biosurfactant was verified by measuring the diameter of the oil spreading, measuring the surface tension value and emulsifying capacity against xylene, n-pentane, kerosene and crude oil. The experimental result showed three strains (S2, S3, S6) had the better surface activity. Among the three strains, the best results were achieved when using S2 strain. The diameter of the oil spreading of the biosurfactant produced by S2 strain was 14 cm, its critical micelle concentration (CMC) was 21.8 mg/l and the interfacial tension between crude oil and biosurfactant solution produced by S2 strain reduced to 25.7 mN/m. The biosurfactant produced by S2 strain was capable of forming stable emulsions with various hydrocarbons, such as xylene, n-pentane, kerosene and crude oil. After S2 strain treatment, the reduction rate of oil viscosity was 51 % and oil freezing point reduced by 4 °C. Keywords Biosurfactant Emulsification activity Interfacial tensions Surface tension Critical micelle concentration (CMC)
J. Liu (&) Y. Chen Y. Jia Provincial Key Laboratory of Oil and Gas Chemical Technology, College of Chemistry and Chemical Engineering, Northeast Petroleum University, Daqing 163318, Heilongjiang, China e-mail: [email protected] R. Xu School of Life Sciences, Xiamen University, Xiamen 361005, Fujian, China
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Introduction The chemical synthesized surfactants have a wide range of applications in industries [1, 2]. However, the chemical synthesized surfactants are expensive and they causing environmental pollution. Biosurfactants are natural products produced by microorganisms. The biosurfactants have unique properties that chemical synthesized surfactants do not have, such as high surface activity, environmental friendliness, biodegradable and good anti-microbial activity at extreme temperatures, pH and salinity [3–5]. These advantages allow biosurfactants to be a substitute for chemical synthesized surfactants. The potential development of a large number of biosurfactant-producing strains has been not found. The research on the breeding of high-yielding biosurfactantproducing strains has important significance. The most effective biosurfactant can reduce the surface tension of water from 72 mN/m to values in the range of 25-30 mN/m [6]. Therefore, the screening and evaluation of efficient biosurfactant-producing strains have wide biological and economic significance. There are many areas of application where biosurfactants can be used, such as in industries and environmental restoration [7, 8]. Biosurfactants have uses in the petroleum industry, such as enhanced oil recovery and tra
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