The polyhydroxyalkanoate (PHA) synthase 1 of Pseudomonas sp. H9 synthesized a 3-hydroxybutyrate-dominant hybrid of short- and medium-chain-length PHA

Chung-Hsien Liu; Houng-Yung Chen; Yuh-Ling Lee Chen; Der-Shyan Sheu

doi:10.1016/j.enzmictec.2020.109719

The polyhydroxyalkanoate (PHA) synthase 1 of Pseudomonas sp. H9 synthesized a 3-hydroxybutyrate-dominant hybrid of short- and medium-chain-length PHA

Enzyme Microb Technol. 2021 Feb:143:109719. doi: 10.1016/j.enzmictec.2020.109719. Epub 2020 Nov 27.

Authors

Chung-Hsien Liu¹, Houng-Yung Chen², Yuh-Ling Lee Chen², Der-Shyan Sheu³

Affiliations

¹ Department of Marine Biotechnology, National Kaohsiung University of Science and Technology, Kaohsiung, 81157, Taiwan.
² Department of Oceanography, National Sun Yat-sen University, Kaohsiung, 80424, Taiwan.
³ Department of Marine Biotechnology, National Kaohsiung University of Science and Technology, Kaohsiung, 81157, Taiwan; Department of Oceanography, National Sun Yat-sen University, Kaohsiung, 80424, Taiwan. Electronic address: sds@nkust.edu.tw.

PMID: 33375979
DOI: 10.1016/j.enzmictec.2020.109719

Abstract

Pseudomonas sp. H9 (H9), an environmental strain isolated from a riverbank soil sample collected in southern Taiwan, is Gram-negative and shares a 99 % sequence identity to Pseudomonas putida KT2440 based on 16S rRNA gene analysis. H9 produced novel polyhydroxyalkanoates (PHA) including a hybrid PHA, comprised of 3-hydroxyvalerate (37 mol%) and medium-chain-length (MCL) monomers from valerate, as well as a 3-hydroxyhexanoate-dominant (93 mol%) MCL-PHA from hexanoate. Next-generation sequencing analysis showed H9 had a typical class II PHA operon, consisted of phaC1_H9-phaZ_H9-phaC2_H9, in which phaC1_H9 was the sole active PHA synthase in H9. Deletion of phaC1_H9 gene led to a complete loss of its PHA accumulation capability. Knockout of phaC2_H9 gene, in contrast, affected neither bacterial growth nor PHA accumulation. When co-expressed with the phaAB genes of Ralstonia eutropha H16 in the PHA mutant strain Pseudomonas sp. H9ΔC1, phaC1_H9 synthesized a hybrid PHA consisted of 3-hydroxybutyrate (3HB) (75 mol%) and MCL-monomers, confirmed in analyses using hot-acetone fractionation and ¹³C-NMR spectroscopy. As a novel PHA synthase, PhaC1_H9 possesses a broad substrate specificity to synthesize a hybrid of SCL- and MCL-PHA, known to have many mechanical properties for potential applications.

Keywords: Hybrid PHA; PHA synthase; Polyhydroxyalkanoate; Substrate specificity.

MeSH terms

3-Hydroxybutyric Acid
Acyltransferases / genetics
Polyhydroxyalkanoates*
Pseudomonas / genetics
RNA, Ribosomal, 16S

Substances

Polyhydroxyalkanoates
RNA, Ribosomal, 16S
Acyltransferases
poly(3-hydroxyalkanoic acid) synthase
3-Hydroxybutyric Acid