Production of medium chain length poly-3-hydroxyalkanoates (mcl-PHAs) in Escherichia coli is reported for the first time. To produce PHA in E. coli, a PHA polymerase encoding gene (phaC2) of Pseudomonas oleovorans GPo1 was introduced into various E. coli strains and fatty acid oxidation mutants thereof. Of these, E. coli fadA/B, E. coli fadRfadA or E. coli fadRfadB mutants, which are defective in specific steps of the fatty acid β-oxidation pathway, allowed production of mcl-PHAs from fatty acids ranging from octanoate to octadecanoate. Maximum amounts of about 10% PHA of total cell dry weight (w/w) were found. The predominant monomers found in these PHAs were always the same, independently of the chain length of the supplied fatty acids: 3-hydroxyoctanoate for even chain length fatty acids and a combination of 3-hydroxynonanoate and 3-hydroxyheptanoate for odd chain length fatty acids. Since the monomer composition of the produced polymer was independent of the fatty acid chain length, β-oxidation occurs in these β-oxidation mutants. The polymer may be hydrolyzed to yield interesting optically active monomers and their esters.
这是首次报道在大肠杆菌中生产中链长度的聚-3-羟基烷酸(cl-PHAs)。为了在大肠杆菌中生产 PHA,我们将油假单胞菌 GPo1 的 PHA 聚合酶编码
基因(phaC2)导入各种大肠杆菌菌株及其
脂肪酸氧化突变体中。其中,大肠杆菌 fadA/B、大肠杆菌 fadRfadA 或大肠杆菌 fadRfadB 突变体在
脂肪酸 β 氧化途径的特定步骤中存在缺陷,可利用从
辛酸酯到
十八酸酯的
脂肪酸生产 mcl-PHA。研究发现,PHA 的最大含量约为细胞总干重的 10%。这些 PHA 中的主要单体始终相同,与所提供
脂肪酸的链长无关:偶数链长的
脂肪酸为
3-羟基辛酸酯,奇数链长的
脂肪酸为
3-羟基壬酸酯和
3-羟基庚酸酯的组合。由于所生产聚合物的单体组成与
脂肪酸链长无关,因此在这些 β-氧化突变体中会发生 β-氧化。这种聚合物可通过
水解产生有趣的光学活性单体及其
酯类。