European Journal of Engineering and Technology Vol. 3 No. 6, 2015 ISSN 2056-5860 Progressive Academic Publishing, UK Page 27 www.idpublications.org BIOSURFACTANT PRODUCTION BY INDIGENEOUS PSEUDOMONAS AND BACILLUS SPECIES ISOLATED FROM AUTO-MECHANIC SOIL ENVIRONMENT TOWARDS MICROBIAL ENHANCED OIL RECOVERY S. E. Agarry * , K. K. Salam, A. Arinkoola & M. O. Aremu Biochemical and Petroleum Engineering Laboratories, Department of Chemical Engineering, Ladoke Akintola University of Technology, P. M. B. 4000, Ogbomoso, NIGERIA Corresponding author: E-mail: sam_agarry@yahoo.com ABSTRACT The objective of this work was to study the biosurfactant production of two indigenous organisms isolated from auto-mechanic polluted soil environment and to evaluate their oil recovery efficiency. In this study, six bacteria were isolated from auto-mechanic polluted soil environment. Isolated strains were identified by morphological, biochemical, and physiological characterization. Among these, two isolates (Bacillus sp. and Pseudomonas sp.) were further selected and used for the production of biosurfactant. Bacillus and Pseudomonas species were grown in mineral salt medium (MSM) with addition of 3% (w/v) glucose. In the growth kinetic study, the maximum biosurfactant production occurred at 120 h of incubation (2.2 g/l) and maximum biomass was observed at 120 h (3.2 g/l) for Bacillus isolate. While for Pseudomonas isolate, the maximum biosurfactant production occurred at 96 h of incubation (2 g/l) and maximum biomass at 72 h (2.6 g/l). Different nitrogen sources as well as the effect of salinity and temperature were evaluated for their effect on biosurfactant production. Yeast extract and sodium nitrate was the best nitrogen source for the production of biosurfactant by Bacillus and Pseudomonas isolates, respectively. The environmental factors such as temperature 30 o C and salinity (0.2% w/v) were found to be optimum for the biosurfactant production. The stability of the biosurfactant was investigated at different salinities and temperature. The biosurfactant was effective at very low concentrations over a wide range of temperature and salt concentration. The results obtained showed that the biosurfactants have a good oil recovery efficiency thus being more attractive to be applied in microbial enhanced oil recovery. Keywords: Biosurfactant; Bacillus species; Emulsification index; Pseudomonas species; Surface tension; Microbial enhanced oil recovery. INTRODUCTION Microbial enhanced oil recovery (MEOR) is the method of using microorganisms and their metabolic by-products to improve recovery of oil from the reservoirs after secondary oil recovery (Bryant and Lockhart 2002; McInerney et al. 2005; Lazar et al. 2007). This technique is based on in situ growth and metabolism of selected microorganism in the reservoir rock with certain nutrients. The microorganism produce gases and/or chemicals in the formation such as polymer, acids, gases, surfactants and biomass Production of these metabolites in the formation changes fluid and rock properties of the reservoir and improves the sweep efficiency. These changes respectively, increase the oil production from the reservoir. The idea of MEOR was first proposed by Beckmann (1926) when he published results on the possibility to use microbial metabolites to improve the oil production rate. Additional work by Zoebell, 1947 showed that these metabolites are analogue to the chemicals used in chemical enhanced oil recovery and are expected to perform the job of residual oil recovery. There are three major mechanisms by which microorganisms may contribute to enhanced oil recovery: i) microorganisms can produce biosurfactants and