title: Heterologous production of Pseudomonas aeruginosa rhamnolipid under anaerobic conditions for microbial enhanced oil recovery.
abstract: OBJECTIVE
  The ex situ application of rhamnolipid to enhance oil recovery is costly and complex in terms of rhamnolipid production and transportation, while in situ production of rhamnolipid is restricted by the oxygen-deficient environments of oil reservoirs. To overcome the oxygen-limiting conditions and to circumvent the complex regulation of rhamnolipid biosynthesis in Pseudomonas aeruginosa, an engineered strain Pseudomonas stutzeri Rhl was constructed for heterologous production of rhamnolipid under anaerobic conditions.
  
  
  RESULTS
  The rhlABRI genes for rhamnolipid biosynthesis were cloned into a facultative anaerobic strain Ps. stutzeri DQ1 to construct the engineered strain Rhl. Anaerobic production of rhamnolipid was confirmed by thin layer chromatography and Fourier transform infrared analysis. Rhamnolipid product reduced the air-water surface tension to 30.3 mN m(-1) and the oil-water interfacial tension to 0.169 mN m(-1). Rhl produced rhamnolipid of 1.61 g l(-1) using glycerol as the carbon source. Rhl anaerobic culture emulsified crude oil up to EI24 ≈ 74. An extra 9.8% of original crude oil was displaced by Rhl in the core flooding test.
  
  
  CONCLUSIONS
  Strain Rhl achieved anaerobic production of rhamnolipid and worked well for enhanced oil recovery in the core flooding model. The rhamnolipid produced by Rhl was similar to that of the donor strain SQ6.
  
  
  CONCLUSIONS
  This is the first study to achieve anaerobic and heterologous production of rhamnolipid. Results demonstrated the potential feasibility of Rhl as a promising strain to enhance oil recovery through anaerobic production of rhamnolipid.
authors.affiliation: Key Laboratory of Pollution Ecology and Environmental Engineering, Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang, Liaoning Province, China; University of Chinese Academy of Sciences, Beijing, China.
authors.forename: F
authors.initials: F
authors.lastname: Zhao
authors.forename: R
authors.initials: R
authors.lastname: Shi
authors.forename: J
authors.initials: J
authors.lastname: Zhao
authors.forename: G
authors.initials: G
authors.lastname: Li
authors.forename: X
authors.initials: X
authors.lastname: Bai
authors.forename: S
authors.initials: S
authors.lastname: Han
authors.forename: Y
authors.initials: Y
authors.lastname: Zhang
mesh_terms: D000693:Anaerobiosis; D060846:Cell Engineering; D005285:Fermentation; D006017:Glycolipids / Q000096:biosynthesis* / Q000737:chemistry; D010578:Petroleum; D011550:Pseudomonas aeruginosa / Q000235:genetics*; D044223:Pseudomonas stutzeri / Q000235:genetics* / Q000378:metabolism; D013500:Surface Tension; D013501:Surface-Active Agents / Q000737:chemistry
chemical_list: D006017:Glycolipids; D010578:Petroleum; D013501:Surface-Active Agents; C418382:rhamnolipid
keywords: Pseudomonas sp; glycerol; microbial enhanced oil recovery; rhamnolipid; rhlABRI