Meng De-Chuan, Chen Guo-Qiang
MOE Key Lab of Bioinformatics, School of Life Science, Tsinghua-Peking Center for Life Sciences, Tsinghua University, Beijing, 100084, China.
Adv Biochem Eng Biotechnol. 2018;162:147-174. doi: 10.1007/10_2017_3.
Microbial polyhydroxyalkanoates (PHA) are a family of biodegradable and biocompatible polyesters which have been extensively studied using synthetic biology and metabolic engineering methods for improving production and for widening its diversity. Synthetic biology has allowed PHA to become composition controllable random copolymers, homopolymers, and block copolymers. Recent developments showed that it is possible to establish a microbial platform for producing not only random copolymers with controllable monomers and their ratios but also structurally defined homopolymers and block copolymers. This was achieved by engineering the genome of Pseudomonas putida or Pseudomonas entomophiles to weaken the β-oxidation and in situ fatty acid synthesis pathways, so that a fatty acid fed to the bacteria maintains its original chain length and structures when incorporated into the PHA chains. The engineered bacterium allows functional groups in a fatty acid to be introduced into PHA, forming functional PHA, which, upon grafting, generates endless PHA variety. Recombinant Escherichia coli also succeeded in producing efficiently poly(3-hydroxypropionate) or P3HP, the strongest member of PHA. Synthesis pathways of P3HP and its copolymer P3HB3HP of 3-hydroxybutyrate and 3-hydroxypropionate were assembled respectively to allow their synthesis from glucose. CRISPRi was also successfully used to manipulate simultaneously multiple genes and control metabolic flux in E. coli to obtain a series of copolymer P3HB4HB of 3-hydroxybutyrate (3HB) and 4-hydroxybutyrate (4HB). The bacterial shapes were successfully engineered for enhanced PHA accumulation.
微生物聚羟基脂肪酸酯（PHA）是一类可生物降解且具有生物相容性的聚酯，人们已运用合成生物学和代谢工程方法对其进行了广泛研究，以提高产量并扩大其多样性。合成生物学已使PHA能够成为组成可控的无规共聚物、均聚物和嵌段共聚物。最近的进展表明，有可能建立一个微生物平台，不仅用于生产具有可控单体及其比例的无规共聚物，还用于生产结构明确的均聚物和嵌段共聚物。这是通过对恶臭假单胞菌或嗜虫假单胞菌的基因组进行工程改造来削弱β-氧化和原位脂肪酸合成途径实现的，这样当脂肪酸被输入细菌后，其在并入PHA链时能保持其原始链长和结构。经过工程改造的细菌能将脂肪酸中的官能团引入PHA，形成功能性PHA，经接枝后可产生无穷无尽的PHA种类。重组大肠杆菌也成功高效地生产出了聚（3-羟基丙酸酯）或P3HP，它是PHA中性能最强的成员。分别组装了P3HP及其3-羟基丁酸酯和3-羟基丙酸酯的共聚物P3HB3HP的合成途径，使其能够从葡萄糖合成。CRISPRi也成功用于同时操纵大肠杆菌中的多个基因并控制代谢通量，以获得一系列3-羟基丁酸酯（3HB）和4-羟基丁酸酯（4HB）的共聚物P3HB4HB。人们成功对细菌形状进行了工程改造以增强PHA积累。
