Enhanced Cadaverine Production by Engineered Escherichia coli Using Soybean Residue Hydrolysate (SRH) as a Sole Nitrogen
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Enhanced Cadaverine Production by Engineered Escherichia coli Using Soybean Residue Hydrolysate (SRH) as a Sole Nitrogen Source Xing Guo 1 & Mengyang Li 1 & Hui Li 1 & Sheng Xu 1 & Xun He 1 Kequan Chen 1
1
& Pingkai Ouyang &
Received: 21 July 2020 / Accepted: 29 September 2020/ # Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract
An economical source of nitrogen is one of the major limiting factors for sustainable cadaverine production. The utilization potential of soybean residue for enhanced cadaverine production by engineered Escherichia coli DFC1001 was investigated in this study. The SRH from soybean residue could get the protein extraction rate (PE) of 67.51% and the degree of protein hydrolysis (DH) of 22.49%. The protein molecular weights in SRH were mainly distributed in 565 Da (72.28%) and 1252 Da (17.11%). These proteins with small molecular weights and concentrated molecular weight distribution were favorable to be transformed by engineered E. coli DFC1001, and then SRH replaced completely yeast powder as an only nitrogen source for cadaverine production. The maximum cadaverine productivity was 0.52 g/L/h, achieved with a constant speed feeding strategy in the optimized SRH fermentation medium containing an initial total sugar concentration of 30 g/L and exogenous added minerals, which indicated that soybean residue could be a potential feedstock for economic cadaverine production. Keywords Cadaverine . Soybean residue hydrolysate . Escherichia coli
Introduction Cadaverine monomer is a widely used platform chemical applied in the synthesis of various polyamide products, polyurethanes, chelating agents, and other additives [1]. At present, cadaverine can be produced through chemical synthesis, whole-cell biocatalysis, and direct bacterial fermentation [2]. For direct bacterial fermentation, the redesigned L-lysine producers * Xun He [email protected]
1
State Key Laboratory of Materials-Oriented Chemical Engineering, College of Biotechnology and Pharmaceutical, Nanjing Tech University, Nanjing 210009, China
Applied Biochemistry and Biotechnology
Corynebacterium glutamicum (C. glutamicum) [3, 4] and Escherichia coli (E. coli) [5, 6] are preferred as cadaverine-producing strains; different biomasses, which are rich in mono- and oligosaccharides such as lignocellulosic hydrolysate and molasses, are used as fermentation substrates [7, 8]. However, the nitrogen contents of these substrates are too low to support microbial cell growth and cadaverine accumulation. Therefore, exogenous nutrients (yeast extract and ammonium salts) are always added into fermentation media [3]. Organic sources of nitrogen such as yeast extract promote cell growth and metabolite accumulation better than inorganic ammonium salts [9], but they are expensive and not suitable for industrial-scale fermentation. Therefore, screening a sustainable nitrogen source is critical and urgently needed for industrial production process of cadaverine. Soybean residue (SR) is a water-insoluble by-product generate
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