Overproduction of Exopolysaccharide Colanic Acid by Escherichia coli by Strain Engineering and Media Optimization
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Overproduction of Exopolysaccharide Colanic Acid by Escherichia coli by Strain Engineering and Media Optimization Hyeong Min Han 1 & In Jung Kim 1 & Eun Ju Yun 1 & Jae Won Lee 2,3 & Yoonho Cho 1 & Yong-Su Jin 2,3 & Kyoung Heon Kim 1 Received: 7 May 2020 / Accepted: 12 August 2020/ # Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract
Colanic acid (CA) is one of the major bacterial exopolysaccharides. Due to its biological activities, CA has a significant commercial value. However, the cultivation conditions have not been optimized for the large-scale production of CA. Here, we constructed a CA-overproducing Escherichia coli strain (ΔwaaF) and statistically optimized its culture media for maximum CA production. Glucose and tryptone were found the optimal carbon and nitrogen sources, respectively. Fractional factorial design indicated tryptone and Na2HPO4 as the critical nutrients for CA production. Through further optimization, we achieved a maximum CA production of 1910.0 mg/L, which is approximately 12-fold higher than the amount obtained using the non-optimized medium initially used. The predicted value of CA production was comparable with experimental value (2052.8 mg/ L) under the optimized conditions. This study constitutes a successful demonstration of media optimization for increased CA production, and paves the way for future research for achieving large-scale CA production. Keywords Colanic acid . Exopolysaccharide . Escherichia coli ΔwaaF . Media optimization . Fractional factorial design . Steepest ascent method . Response surface methodology
Introduction Colanic acid (CA), a negatively charged capsular exopolysaccharide (EPS), is produced by several members of the family Enterobacteriaceae during biofilm formation [1–6]. As a Hyeong Min Han and In Jung Kim contributed equally to this work. Electronic supplementary material The online version of this article (https://doi.org/10.1007/s12010-02003409-4) contains supplementary material, which is available to authorized users.
* Yong-Su Jin [email protected] * Kyoung Heon Kim [email protected] Extended author information available on the last page of the article
Applied Biochemistry and Biotechnology
biofilm component, it contributes to bacterial protection against phage infection and enhances resistance to environmental stressors such as osmotic shock, heat stress, oxidative stress, antimicrobial agents, and dehydration [1, 7–9]. The repeating unit of CA is a hexasaccharide composed of L-fucose, D-galactose, D-glucose, and D-glucuronic acid with a molar ratio of 2:2:1:1 with substitutions by an O-acetyl group and a pyruvate ketal [1, 10–12]. For the CA biosynthesis in Escherichia coli, four different nucleoside-sugar precursors (GDP-L-fucose, UDP-D-glucose, UDP-D-glucuronate, and UDP-D-galactose) are required. UDP-D-glucose is the common precursor, which can be derived from glycolytic pathway, to synthesize UDP-Dglucuronate and UDP-D-galactose. The synthesis of GDP-L-fucose is highly connected with CA cluster composed of 20
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