Efficient, Simple Production of Corresponding Alcohols from Supplemented C 2 -C 8 Carboxylic Acids in Escherichia coli U
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pISSN 1226-8372 eISSN 1976-3816
RESEARCH PAPER
Efficient, Simple Production of Corresponding Alcohols from Supplemented C2-C8 Carboxylic Acids in Escherichia coli Using Acyl-CoA Transferase from Megasphaera hexanoica Hyojung Park, Byoung Seung Jeon, and Byoung-In Sang
Received: 26 May 2020 / Revised: 5 June 2020 / Accepted: 7 June 2020 © The Korean Society for Biotechnology and Bioengineering and Springer 2020
Abstract The accumulation of short-chain carboxylic acids (SCCAs), such as acetic acid (C2), propionic acid (C3), butyric acid (C4), and valeric acid (C5), produced by acetogens in the anaerobic digestion (AD) process hampers the maintenance of stable AD processes in biomethane production. The conversion of various SCCAs to the corresponding alcohols can be a good solution not only for utilizing abandoned or harmful SCCAs and producing useful alcohols but also for increasing the efficiency of the biogas production process. ACT01_02765 (acyl-CoA transferase) from Megasphaera hexanoica quickly and easily converted C2-C8 carboxylic acids into the corresponding alcohols in Escherichia coli with AdhE2 (alcohol dehydrogenase) from Clostridium acetobutylicum. E. coli (ACT01_02765 and AdhE2) converted carboxylic acids to the corresponding alcohols with a conversion yield that was approximately 40 times higher and a conversion rate that was approximately 10-50 times faster than those of E. coli (Ptb-Buk and AdhE2). The enzymatic machinery in E. coli (ACT01_02765 and AdhE2) is effective for carboxylic acids of different carbon chain lengths, resulting in the production of propanol, butanol, pentanol, hexanol, heptanol, and octanol. Keywords: acyl-CoA transferase, alcohol, carboxylic acid, Megasphaera hexanoica
Hyojung Park, Byoung Seung Jeon, Byoung-In Sang* Department of Chemical Engineering, Hanyang University, Seoul 04763, Korea Tel: +82-2-2220-2328; Fax: +82-2-2220-4716 E-mail: [email protected]
1. Introduction Anaerobic digestion (AD) is considered a typical process for treating organic wastes. In addition to solving environmental problems, AD can also produce biogas as an energy source with fertilizer, soil conditioners, livestock bedding, and so on. However, AD is strongly dependent on several operating conditions, such as pH, temperature, and hydraulic retention time (HRT) [1-5]. In particular, the accumulation of short-chain carboxylic acids (SCCAs) such as acetic acid (C2), propionic acid (C3), butyric acid (C4), and valeric acid (C5) that are produced by acetogens in the AD process hampers stable AD processes in biomethane production [6]. Increasing the conversion rate of SCCAs into biomethane with acetoclastic methanogens has been a recent research topic in the AD process; however, the activity of acetoclastic methanogens is inhibited by ammonia, which is usually present during the AD process, and by competition with hydrogenotrophic methanogen and sulfate-reducing bacteria [4,7]. The conversion of various SCCAs to corresponding alcohols can be a good solution not only for utilizing abandoned or h
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