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Microbial Bioplastics Production and Degradation

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Front. Bioeng. Biotechnol. | doi: 10.3389/fbioe.2018.00178

Low Carbon Concentration Feeding Improves Medium-Chain-Length Polyhydroxyalkanoate Production in Escherichia coli strains with Defective β-Oxidation

 Takeharu Tsuge1*,  Fakhrul Ikhma Mohd Fadzil1, Shoji MIzuno1, Ayaka Hiroe1, 2 and  Christopher Nomura3
  • 1Tokyo Institute of Technology, Japan
  • 2Tokyo University of Agriculture, Japan
  • 3The State University of New York (SUNY), United States

Medium-chain-length (MCL) polyhydroxyalkanoates (PHAs) of near homopolymeric composition are unnatural polymers, having almost identical repeating units throughout the polymer chain. These homopolymeric PHAs can be produced by β-oxidation defective bacterial hosts. Escherichia coli is an attractive workhorse for the production of such genetically engineered PHAs; however, achieving efficient production of the near homopolymers by β-oxidation defective strains is a major challenge because of a lack of process development studies. In order to address this issue, we investigated the optimization of carbon feeding for efficient production of MCL-PHAs by an E. coli strain with defective β-oxidation, LSBJ. Engineered bacteria were cultured in shake-flasks with intermittent feeding of a fatty acid substrate [either decanoate (C10) or dodecanoate (C12)] at various concentrations together with a co-carbon source (glucose, glycerol, or xylose) in order to support cell growth. It was found that feeding low concentrations of both fatty acids and co-carbon sources led to an enhanced production of MCL-PHAs. Additionally, the supplementation of yeast extract improved cell growth, resulting in achieving higher titers of MCL-PHA. As a result, poly(3-hydroxydecanoate) [P(3HD)] and poly(3-hydroxydodecanoate) [P(3HDD)] were produced up to 5.44 g/L and 3.50 g/L, respectively, as near homopolymers by employing the developed feeding strategy. To the best of our knowledge, we record the highest titer of P(3HD) ever reported so far.

Keywords: fatty acid, near homopolymer, Escherichia coli, MCL-PHA, Carbon feeding

Received: 19 Aug 2018; Accepted: 07 Nov 2018.

Edited by:

Young-Cheol Chang, Muroran Institute of Technology, Japan

Reviewed by:

Christopher J. Brigham, Wentworth Institute of Technology, United States
Hui Wu, East China University of Science and Technology, China  

Copyright: © 2018 Tsuge, Mohd Fadzil, MIzuno, Hiroe and Nomura. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence: Dr. Takeharu Tsuge, Tokyo Institute of Technology, Meguro, Japan, TSUGE.T.AA@M.TITECH.AC.JP