Efficient biosynthesis of polysaccharide welan gum in heat shock protein-overproducing Sphingomonas sp. via temperature-
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RESEARCH PAPER
Efficient biosynthesis of polysaccharide welan gum in heat shock protein‑overproducing Sphingomonas sp. via temperature‑dependent strategy Ping Zhu1 · Yijing Zhan1 · Cheng Wang1 · Xiaoliu Liu1 · Liming Liu2 · Hong Xu1 Received: 15 April 2020 / Accepted: 26 August 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract Cell growth and product formation are two critical processes in polysaccharide welan biosynthesis, but the conflict between them is often encountered. In this study, a temperature-dependent strategy was designed for two-stage welan production through overexpressing heat shock proteins in Sphingomonas sp. The first stage was cell growth phase with higher TCA cycle activity at 42 °C; the second stage was welan formation phase with higher precursor synthesis pathway activity at 37 °C. The highest welan concentration 37.5 g/L was achieved after two-stage process. Ultimately, this strategy accumulated welan yield of 79.2 g/100 g glucose and productivity of 0.62 g/L/h at 60 h, which were the best reported results so far. The duration of fermentation was shortened. Besides, rheological behavior of welan gum solutions remained stable at wide range of temperature, pH, and NaCl. These results indicated that this approach efficiently improved welan synthesis. Keywords Welan gum · Biosynthesis · Heat shock protein · Two-stage fermentation · Temperature dependent
Introduction Welan gum is a type of biodegradable microbial polysaccharide [1]. It is widely used in food, medicine, water clarification, concrete additives, oil recovery, and other fields [2]. Due to its excellent rheological properties, such as salt resistance, thermotolerance, and good pH stability, it becomes the few eco-friendly oil displacement agents for oil recovery besides xanthan gum [3–5]. Welan gum can be achieved Ping Zhu and Yijing Zhan contributed equally to this study. Electronic supplementary material The online version of this article (https://doi.org/10.1007/s00449-020-02438-x) contains supplementary material, which is available to authorized users. * Liming Liu [email protected] * Hong Xu [email protected] 1
State Key Laboratory of Materials‑Oriented Chemical Engineering, College of Food Science and Light Industry, Nanjing Tech University, No.30 South Puzhu Road, Pukou District, Nanjing 211816, China
State Key Laboratory of Food Science and Technology, Jiangnan University, 1800 Lihu Road, Wuxi 214122, China
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through strain fermentation [6]. However, the current conversion rate of welan is still much lower (below 50%) than the conversion rate of xanthan (above 70%) [7–10]. Low conversion rate is the bottleneck for reducing production costs and market price. Efficient welan conversion rate could not be rationally enhanced due to complicated and uncontrollable metabolic network in Sphingomonas sp. (Fig. 1). Welan gum production by precursors synthesis pathway conflicts with biomass formation by tricarboxylic acid (TCA) cycle [11]. Genetic metabolic manipulation by switching on precur
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