AUTHOR=Shi Mengxun , Li Mengdi , Yang Anran , Miao Xue , Yang Liu , Pandhal Jagroop , Zou Huibin 

TITLE=Class I Polyhydroxyalkanoate (PHA) Synthase Increased Polylactic Acid Production in Engineered Escherichia Coli

JOURNAL=Frontiers in Bioengineering and Biotechnology

VOLUME=10

YEAR=2022

URL=https://www.frontiersin.org/journals/bioengineering-and-biotechnology/articles/10.3389/fbioe.2022.919969

DOI=10.3389/fbioe.2022.919969

ISSN=2296-4185

ABSTRACT=<p>Polylactic acid (PLA), a homopolymer of lactic acid (LA), is a bio-derived, biocompatible, and biodegradable polyester. The evolved class II PHA synthase (PhaC1<sub><italic>Ps</italic>6-19</sub>) was commonly utilized in the <italic>de novo</italic> biosynthesis of PLA from biomass. This study tested alternative class I PHA synthase (PhaC<sub><italic>Cs</italic></sub>) from <italic>Chromobacterium</italic> sp. USM2 in engineered <italic>Escherichia coli</italic> for the <italic>de novo</italic> biosynthesis of PLA from glucose. The results indicated that PhaC<sub><italic>Cs</italic></sub> had better performance in PLA production than that of class II synthase PhaC1<sub><italic>Ps</italic>6-19</sub>. In addition, the <italic>sulA</italic> gene was engineered in PLA-producing strains for morphological engineering. The morphologically engineered strains present increased PLA production. This study also tested fused propionyl-CoA transferase and lactate dehydrogenase A (fused Pct<sub><italic>Cp</italic></sub>/LdhA) in engineered <italic>E. coli</italic> and found that fused Pct<sub><italic>Cp</italic></sub>/LdhA did not apparently improve the PLA production. After systematic engineering, the highest PLA production was achieved by <italic>E. coli</italic> MS6 (with <italic>PhaC</italic><sub><italic>Cs</italic></sub> and <italic>sulA</italic>), which could produce up to 955.0 mg/L of PLA in fed-batch fermentation with the cell dry weights of 2.23%, and the average molecular weight of produced PLA could reach 21,000 Da.</p>