Biotechnology and Bioprocess Engineering 2022; 27(2): 268-275  
Production of Polyhydroxyalkanoates with the Fermentation of Methylorubrum extorquens Using Formate as a Carbon Substrate
Woojin Chang, Jihee Yoon, and Min-Kyu Oh
Woojin Chang, Jihee Yoon, Min-Kyu Oh*
Department of Chemical and Biological Engineering, Korea University, Seoul 02841, Korea
Tel: +82-2-3290-3308, Fax: +82-2-926-6102
E-mail: mkoh@korea.ac.kr
These authors contributed equally to this work.
Received: February 18, 2022; Revised: March 2, 2022; Accepted: March 3, 2022; Published online: April 30, 2022.
© The Korean Society for Biotechnology and Bioengineering. All rights reserved.

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
Abstract
Deriving both carbon and energy from formate, a single-carbon substrate, for the microbial production of value-added products allows its use as the main feedstock in biorefinery, with consequent environmental and economic benefits. Methylorubrum extorquens AM1, a strain capable of growth solely on formate, is a known producer of the biopolymer polyhydroxyalkanoate (PHA), during nitrogen deficient growth. Based on findings from our previous report, the gene ftfL was selected for overexpression to enhance growth and PHA production using formate. Its over expression in a poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV)-producing strain yielded improved growth and a 1.4-fold increase in PHBV production. The strain could thus be tested for long-term fermentation, intended for optimized growth and production in formate. A customized fermentation regimen was established by incorporating both the conventional two-phase fermentation method for PHA production and a repeated fed-batch fermentation process designed to resolve the problem of sodium accumulation. The poly-3-hydroxybutyrate and PHBV copolymer-producing strains resulted in 11.07 g/L and 2.76 g/L of bio-degradable polymers, respectively, in the fermentation process.
Keywords: Methylorubrum extorquens, formate, polyhydroxyalkanoate, repeated fed-batch fermentation


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