In Vivo Characterization and Application of the PHA Synthase from Azotobacter vinelandii for the Biosynthesis of Polyhydroxyalkanoate Containing 4-Hydroxybutyrate.

Pei-Shze Mok,Kumar Sudesh,Nazalan Najimudin,Bor-Chyan Jong,Jo-Ann Chuah,Pauline-Woan-Ying Liew

doi:10.3390/polym13101576

Pei-Shze Mok, Kumar Sudesh + Show 4 more

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https://doi.org/10.3390/polym13101576

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Journal: Polymers	Publication Date: May 14, 2021
Citations: 2	License type: CC BY 4.0

Affiliation: Universiti Sains Malaysia, Malaysian Nuclear Agency

Abstract

Polyhydroxyalkanoate (PHA) is a biodegradable thermoplastic naturally synthesized by many microorganisms, and the PHA synthase (PhaC) is known to be the key enzyme involved in determining the material properties and monomer composition of the produced PHA. The ability to exploit widely distributed, commonly found soil microorganisms such as Azotobacter vinelandii to synthesize PHA containing the lipase-degradable 4-hydroxybutyrate (4HB) monomer will allow for convenient production of biocompatible and flexible PHA. Comparisons between the A. vinelandii wild type and mutant strains, with and without a surface layer (S-layer), respectively, in terms of gene or amino acid sequences, synthase activity, granule morphology, and PHA productivity, revealed that the S-layer is the sole factor affecting PHA biosynthesis by A. vinelandii. Based on PHA biosynthesis using different carbon sources, the PhaC of A. vinelandii showed specificity for short-chain-length PHA monomers, making it a member of the Class I PHA synthases. In addition, it was proven that the PhaC of A. vinelandii has the inherent ability to polymerize 4-hydroxybutyrate (4HB) and the mediated accumulation of PHA with 4HB fractions ranging from 10 mol% to as high as 22 mol%. The synthesis of biocompatible PHA containing tailorable amounts of 4HB with an expanded range of elasticity and lipase-degradability will enable a wider range of applications in the biomedical field.

Highlights

IntroductionThe widespread usage of petroleum-based synthetic plastic in various applications such as mobile and transport, construction and building, as well as entertainment activities, has created severe environmental pollution and depletion of petroleum
The demand for synthetic plastics has increased as the human population increases
PHA synthases from both A. vinelandii strains were evaluated in terms of expression activity and gene sequences

Summary

Introduction

The widespread usage of petroleum-based synthetic plastic in various applications such as mobile and transport, construction and building, as well as entertainment activities, has created severe environmental pollution and depletion of petroleum. Limitations in resources needed for the synthesis of plastics triggered many researchers to develop a new type of plastic. Polyhydroxyalkanoate (PHA) was found to have similar properties to synthetic plastics such as polypropylene (PP) and could be a potential candidate to replace certain types of petroleum-based synthetic plastics. PHA is biosynthesized by microbial cells under nutrient imbalance. The PHA granules are stored in the body of microbial cells as carbon and energy reserves for when the surrounding environment lacks a carbon source for cell survival [1,2,3,4]

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