Effective enhancement of short-chain-length-medium-chain-length polyhydroxyalkanoate copolymer production by coexpression of genetically engineered 3-ketoacyl-acyl-carrier-protein synthase III (fabH) and polyhydroxyalkanoate synthesis genes
Effective enhancement of short-chain-length-medium-chain-length polyhydroxyalkanoate copolymer production by coexpression of genetically engineered 3-ketoacyl-acyl-carrier-protein synthase III (fabH) and polyhydroxyalkanoate synthesis genes
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DOI：
10.1021/bm049959v
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发表时间：
2004-07-01
影响因子：
6.2
通讯作者：
Doi, Y
中科院分区：
文献类型：
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作者：
Nomura, CT;Tanaka, T;Doi, Y
聚羟基链烷酸酯（PHA）是可生物降解的聚酯，其具有取决于聚合物中单体单元的侧基的长度的各种各样的物理性质。主要由短链长度（SCL）单体组成的PHA通常是刚性和脆性的，而主要由中链长度（MCL）单体组成的PHA本质上是弹性体的。SCL-MCL PHA共聚物可以具有两种状态之间的性质，这取决于共聚物中SCL和MCL单体的比率。希望阐明新的和低成本的方法来从可再生资源生产主要由SCL单体单元和小摩尔%的MCL单体组成的PHA，因为这种类型的SCL-MCL PHA共聚物与SCL均聚物相比具有上级品质。为了解决这个问题，我们已经创建了重组大肠杆菌菌株。能够从真养罗尔斯通氏菌产生β-酮硫解酶（PhbA）和乙酰乙酰-CoA合酶（PhbB）的大肠杆菌、来自大肠杆菌的遗传工程化的3-酮酰基-ACP合酶III（FabH）和来自假单胞菌属61-3的遗传工程化的PHA脱氢酶（PhaC），以增强从葡萄糖产生SCL-MCL PHA共聚物。具有两种单体供应途径和基因工程PHA脱氢酶的累积效应导致来自葡萄糖的SCL-MCL PHA共聚物的累积量更高。从两个重组E.大肠杆菌菌株，第一种携带phbAB、fabH（F87 T）和phaCl（SCQM）基因，第二种携带phbAB、fabH（F87 W）和phaCl（SCQM）基因。分离的聚合物的热性能和物理性能进行了表征。发现即使在SCL-MCL PHA共聚物中非常低摩尔%的MCL单体对共聚物的热性能也具有显著影响。
Polyhydroxyalkanoates (PHAs) are biodegradable polyesters that have a wide variety of physical properties dependent on the lengths of the pendant groups of the monomer units in the polymer. PHAs composed of mostly short-chain-length (SCL) monomers are often stiff and brittle, whereas PHAs composed of mostly medium-chain-length (MCL) monomers are elastomeric in nature. SCL-MCL PHA copolymers can have properties between the two states, dependent on the ratio of SCL and MCL monomers in the copolymer. It is desirable to elucidate new and low cost ways to produce PHA composed of mostly SCL monomer units with a small mol % of MCL monomers from renewable resources, since this type of SCL-MCL PHA copolymer has superior qualities compared to SCL homopolymer. To address this issue, we have created strains of recombinant E. coli capable of producing beta-ketothiolase (PhbA) and acetoacetyl-CoA synthase (PhbB) from Ralstonia eutropha, genetically engineered 3-ketoacyl-ACP synthase III (FabH) from Escherichia coli, and genetically engineered PHA synthases (PhaC) from Pseudomonas sp. 61-3 to enhance the production of SCL-MCL PHA copolymers from glucose. The cumulative effect of having two monomer-supplying pathways and genetically engineered PHA synthases resulted in higher accumulated amounts of SCL-MCL PHA copolymer from glucose. Polymers were isolated from two recombinant E. coli strains, the first harboring the phbAB, fabH(F87T), and phaCl(SCQM) genes and the second harboring the phbAB, fabH(F87W), and phaCl(SCQM) genes. The thermal and physical properties of the isolated polymers were characterized. It was found that even a very low mol % of MCL monomer in a SCL-MCL PHA copolymer had dramatic effects on the thermal properties of the copolymers.