Increased Production and Molecular Weight of Artificial Polyhydroxyalkanoate Poly(2-hydroxybutyrate) Above the Glass Transition Temperature Threshold
Increased Production and Molecular Weight of Artificial Polyhydroxyalkanoate Poly(2-hydroxybutyrate) Above the Glass Transition Temperature Threshold
复制标题
DOI：
10.3389/fbioe.2019.00177
复制
发表时间：
2019-07-24
影响因子：
5.7
通讯作者：
Kageyama, Yuki
中科院分区：
文献类型：
--
作者：
Matsumoto, Ken'ichiro;Kageyama, Yuki
聚（2-羟基丁酸酯）[P（2 HB）]是使用工程化的2-羟基链烷酸酯聚合PHA合酶合成的人工聚羟基链烷酸酯（PHA）。在本研究中，温度对P（2 HB）合成的影响进行了研究。将含有PHA合成基因的重组大肠杆菌与2 HB和3-羟基丁酸（3 HB）补充物一起在24至36 ℃的不同温度下培养，分别用于合成P（2 HB）和天然PHA P（3 HB）。在32-34 ℃的阈值温度下，P（2 HB）的产量和分子量显著增加。在P（3 HB）的合成过程中没有观察到这种趋势。值得注意的是，阈值温度接近P（2 HB）的玻璃化转变温度（T-g）（30 ℃），而P（3 HB）的T-g（4 ℃）远低于培养温度。结果表明，聚合物链的热运动影响所获得的聚合物的产量和分子量。根据结果，PHA的产量和分子量在阈值温度下急剧变化，这与聚合物的Tg有关。该假设应该适用于PHA，并可能解释了生物合成T-g为60 ℃的高分子量聚乳酸酯均聚物的能力。
Poly(2-hydroxybutyrate) [P(2HB)] is an artificial polyhydroxyalkanoate (PHA) synthesized using engineered 2-hydroxyalkanoate-polymerizing PHA synthase. In the present study, the effect of temperature on P(2HB) synthesis was investigated. Recombinant Escherichia coli harboring PHA synthetic genes were cultivated with 2HB and 3-hydroxybutyrate (3HB) supplementation at varied temperatures ranging from 24 to 36 degrees C for the synthesis of P(2HB) and natural PHA P(3HB), respectively. P(2HB) production and its molecular weight increased considerably at a threshold temperature of 32-34 degrees C. The trend was not observed during the synthesis of P(3HB). Notably, the threshold temperature was close to the glass transition temperature (T-g) of P(2HB) (30 degrees C), while the T-g of P(3HB) (4 degrees C) was much lower than the cultivation temperature. The results suggest that thermal motion of the polymer chains influenced the production and molecular weight of the obtained polymer. According to the results, the production and molecular weight of PHA drastically changes at the threshold temperature, which is linked to the T-g of the polymer. The hypothesis should be applicable to PHAs in general, and potentially explains the inability to biosynthesize high-molecular-weight polylactate homopolymer with a T-g of 60 degrees C.