Optimization and Partial Characterization of Biosurfactants Produced by Bacillus Species and Their Potential for Ex-Situ Enhanced Oil Recovery

Abstract

Summary This study aims to test the potential of microbial enhanced oil recovery (MEOR) as an effective alternative in Omani oil fields. In this study, biosurfactants produced by Bacillus licheniformis and Bacillus subtilis strains isolated from oil-contaminated soils from different parts of the Sultanate of Oman were investigated. Eight different minimal production media using different sugars as carbon sources were tested on three of the strains to select the medium that maximized the production of biosurfactants which were indicated by the interfacial tension (IFT) reduction. All isolates were tested on their potential media to screen for the best biosurfactant producer among the available strains. It was found that Bacillus subtilis Strain W19 gave the maximum IFT reduction (46.6 mN/m to 3.28 mN/m) in 16 hours of incubation when grown in a minimal medium containing glucose. The yield of the biosurfactant produced by B. subtilis W19 was 2.5g/L. Critical micelle concentration (CMC) was measured to be 0.4 g/L. The biosurfactant was partially characterized by FT-IR analysis, in which the peaks obtained imply the presence of aliphatic hydrocarbons as well as a peptide-like moiety in the biosurfactant. The cell-free biosurfactant broth produced from Strain W19 was found to be stable over a pH range from 6 to 10 and was most effective at 7. It also showed no loss in surface activity when subjected to various temperatures (60, 80, and 120°C). The biosurfactant also retained almost 60% of its activity even in a high-saline environment up to 20% NaCl (w/v). Further studies were conducted to test the interaction of biosurfactant produced by B. subtilis W19 with porous media in coreflooding experiments as a tertiary-recovery stage. The results showed high potential of using this bacterium during ex-situ MEOR applications in which a total of 23% of residual oil was produced after biosurfactant and concentrated-biosurfactant injection.

Injection of biosurfactant and chemical surfactant following hot water injection to enhance heavy oil recovery

“…The procedure for bacterial growth and biosurfactant production is described in previous studies (Al-Sulaimani et al 2010, 2011a. Briefly, the Bacillus subtilis strain W19 was grown in a minimal media (Table 1) containing 2 % (w/v) glucose and incubated for 16 h at 40°C and at 160 rpm.…”

“…The precipitated biosurfactant was collected by centrifuging at 10,000 rpm, and finally, biosurfactant powder was obtained by spray drying following a standardized protocol at 160-100°C using a Mini spray dryer (Buchi, Switzerland), as previously reported by Al- Sulaimani et al (2010;2011a) .…”

“…This was done to assess the applicability of using this biosurfactant for enhancing oil recovery and comparing its adsorption tendency to that of the commercially available chemical surfactants. Al-Sulaimani et al (2010, 2011a, b, 2012 and Al-Bahry et al (2013a, b) reported that the biosurfactant had potential for enhancing oil recovery since it yielded a total production of 23 % of residual oil. In this study, possibility of enhancing the oil recovery from a Middle East heavy oil field by biosurfactant following hot water injection was investigated.…”

Overview on Chemical-Based, Bio-based and Natural-Based Surfactants in EOR Applications

“…It is complex bio-polymer and has the prospective in moving heavy crude oil from the reservoir. According to Al-Sulaimani et al [5], bio-surfactant produced by Bacillus licheniformis was able to lower the IFT from 46.6 to 3.28 mN m −1 in incubation for 16 h. Bacillus licheniformis are genetically stable and can cause significant IFT reduction in different mediums [6]. Some other bio-surfactants are able to reduce the surface tension of water from 72 to 27 mN m −1 [7].…”

Enhanced Oil Recovery Using Biotransformation Technique on Heavy Crude Oil

“…Bacillus species could produce biosurfactants that aid degradation process by increasing oil emulsification and its accessibility [21][22][23] if suitable nutrients and growth conditions are present.…”