Wang Qinhong, Fang Xiangdong, Bai Baojun, Liang Xiaolin, Shuler Patrick J, Goddard William A, Tang Yongchun
Power, Energy and Environment Research (PEER) Center, Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, USA.
Biotechnol Bioeng. 2007 Nov 1;98(4):842-53. doi: 10.1002/bit.21462.
Rhamnolipid as a potent natural biosurfactant has a wide range of potential applications, including enhanced oil recovery (EOR), biodegradation, and bioremediation. Rhamnolipid is composed of rhamnose sugar molecule and beta-hydroxyalkanoic acid. The rhamnosyltransferase 1 complex (RhlAB) is the key enzyme responsible for transferring the rhamnose moiety to the beta-hydroxyalkanoic acid moiety to biosynthesize rhamnolipid. Through transposome-mediated chromosome integration, the RhlAB gene was inserted into the chromosome of the Pseudomonas aeruginosa PAO1-rhlA(-) and Escherichia coli BL21 (DE3), neither of which could produce rhamnolipid. After chromosome integration of the RhlAB gene, the constitute strains P. aeruginosa PEER02 and E. coli TnERAB did produce rhamnolipid. The HPLC/MS spectrum showed that the structure of purified rhamnolipid from P. aeruginosa PEER02 was similar to that from other P. aeruginosa strains, but with different percentage for each of the several congeners. The main congener (near 60%) of purified rhamnolipid from E. coli TnERAB was 3-(3-hydroxydecanoyloxy) decanoate (C(10)-C(10)) with mono-rhamnose. The surfactant performance of rhamnolipid was evaluated by measurement of interfacial tension (IFT) and oil recovery via sand-pack flooding tests. As expected, pH and salt concentration of the rhamnolipid solution significantly affected the IFT properties. With just 250 mg/L rhamnolipid (from P. aeruginosa PEER02 with soybean oil as substrate) in citrate-Na(2)HPO(4), pH 5, 2% NaCl, 42% of oil otherwise trapped was recovered from a sand pack. This result suggests rhamnolipid might be considered for EOR applications.
鼠李糖脂作为一种高效的天然生物表面活性剂具有广泛的潜在应用，包括提高采收率（EOR）、生物降解和生物修复。鼠李糖脂由鼠李糖分子和β-羟基链烷酸组成。鼠李糖基转移酶1复合物（RhlAB）是负责将鼠李糖部分转移到β-羟基链烷酸部分以生物合成鼠李糖脂的关键酶。通过转座体介导的染色体整合，将RhlAB基因插入到铜绿假单胞菌PAO1-rhlA(-)和大肠杆菌BL21(DE3)的染色体中，这两种菌株都不能产生鼠李糖脂。在RhlAB基因进行染色体整合后，构建的菌株铜绿假单胞菌PEER02和大肠杆菌TnERAB确实产生了鼠李糖脂。HPLC/MS光谱表明，从铜绿假单胞菌PEER02纯化的鼠李糖脂的结构与其他铜绿假单胞菌菌株的结构相似，但几种同系物各自的比例不同。从大肠杆菌TnERAB纯化的鼠李糖脂的主要同系物（接近60%）是带有单鼠李糖的3-(3-羟基癸酰氧基)癸酸酯（C(10)-C(10)）。通过测量界面张力（IFT）和通过填砂驱油试验评估油的采收率来评价鼠李糖脂的表面活性剂性能。正如预期的那样，鼠李糖脂溶液的pH值和盐浓度显著影响IFT性能。在柠檬酸钠-磷酸氢二钠（pH 5、2% NaCl）中，仅250 mg/L的鼠李糖脂（以大豆油为底物的铜绿假单胞菌PEER02产生的）就能从填砂中回收42%原本被困住的油。这一结果表明鼠李糖脂可考虑用于提高采收率应用。
