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Bioconversion of biphenyl to a polyhydroxyalkanoate copolymer by Alcaligenes denitrificans A41

Authors
  • Yajima, Taito1
  • Nagatomo, Mizuki1
  • Wakabayashi, Aiko1
  • Sato, Michio1
  • Taguchi, Seiichi2
  • Maeda, Michihisa1
  • 1 Meiji University, 1-1-1 Higashimita, Tama-ku, Kawsaki, Kanagawa, 214-8571, Japan , Kawsaki (Japan)
  • 2 Tokyo University of Agriculture, 1‐1‐1 Sakuragaoka, Setagaya, Tokyo, 156–8502, Japan , Setagaya (Japan)
Type
Published Article
Journal
AMB Express
Publisher
Springer Berlin Heidelberg
Publication Date
Aug 26, 2020
Volume
10
Issue
1
Identifiers
DOI: 10.1186/s13568-020-01093-5
Source
Springer Nature
Keywords
License
Green

Abstract

A polyhydroxyalkanoate (PHA) copolymer, poly(3-hydroxybutyrate-co-3-hydroxyvalerate) [P(3HB-co-3HV)], was biosynthesized from biphenyl as the sole carbon source using Alcaligenes (currently Achromobacter) denitrificans A41. This strain is capable of degrading polychlorinated biphenyls (PCBs) and biphenyl. This proof-of-concept of the conversion of aromatic chemicals such as the environmental pollutant PCBs/biphenyl to eco-friendly products such as biodegradable polyester PHA was inspired by the uncovering of two genes encoding PHA synthases in the A. denitrificans A41 genome. When the carbon/nitrogen (C/N) ratio was set at 21, the cellular P(3HB-co-3HV) content in strain A41 reached its highest value of 10.1% of the cell dry weight (CDW). A two-step cultivation protocol improved the accumulation of P(3HB-co-3HV) by up to 26.2% of the CDW, consisting of 13.0 mol % 3HV when grown on minimum salt medium without nitrogen sources. The highest cellular content of P(3HB-co-3HV) (47.6% of the CDW) was obtained through the two-step cultivation of strain A41 on biphenyl as the sole carbon source. The purified copolymer had ultra-high molecular weight (weight-average molecular weight of 3.5 × 106), as revealed through gel-permeation chromatography. Based on the genomic information related to both polymer synthesis and biphenyl degradation, we finally proposed a metabolic pathway for the production of P(3HB-co-3HV) associated with the degradation of biphenyl by strain A41.

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