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

Mengxun Shi; Mengdi Li; Anran Yang; Xue Miao; Liu Yang; Jagroop Pandhal; Huibin Zou

doi:10.3389/fbioe.2022.919969

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

Front Bioeng Biotechnol. 2022 Jun 23:10:919969. doi: 10.3389/fbioe.2022.919969. eCollection 2022.

Authors

Mengxun Shi^{1

2}, Mengdi Li¹, Anran Yang¹, Xue Miao¹, Liu Yang¹, Jagroop Pandhal², Huibin Zou^{1

3}

Affiliations

¹ State Key Laboratory Base of Eco-Chemical Engineering, College of Chemical Engineering, Qingdao University of Science and Technology, Qingdao, China.
² Department of Chemical and Biological Engineering, The University of Sheffield, Sheffield, United Kingdom.
³ CAS Key Laboratory of Bio-based Materials, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, Qingdao, China.

Abstract

Polylactic acid (PLA), a homopolymer of lactic acid (LA), is a bio-derived, biocompatible, and biodegradable polyester. The evolved class II PHA synthase (PhaC1 _Ps6-19) was commonly utilized in the de novo biosynthesis of PLA from biomass. This study tested alternative class I PHA synthase (PhaC _Cs ) from Chromobacterium sp. USM2 in engineered Escherichia coli for the de novo biosynthesis of PLA from glucose. The results indicated that PhaC _Cs had better performance in PLA production than that of class II synthase PhaC1 _Ps6-19. In addition, the sulA 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 _Cp /LdhA) in engineered E. coli and found that fused Pct _Cp /LdhA did not apparently improve the PLA production. After systematic engineering, the highest PLA production was achieved by E. coli MS6 (with PhaC _Cs and sulA), 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.

Keywords: biopolyester; class I polyhydroxyalkanoate synthase; degradable polymer; engineered E. coli; polylactic acid.