Screening and characterization of Sphingomonas sp. mutant for welan gum biosynthesis at an elevated temperature

Abstract

The optimal temperature for the microbial polysaccharide fermentation is no higher than 30 °C, which is economically undesirable due to additional cooling cost. To solve this problem in the case of welan gum production, we obtained the high-temperature-tolerant-producing strain, Sphingomonas sp. HT-1 by atmospheric and room-temperature plasma-induced mutation. Using HT-1, we obtained a concentration and 1 % aqueous viscosity of 26.8 ± 0.34 g/L and 3.50 ± 0.05 Pa s at a comparatively higher optimal temperature (37 °C). HT-1 was further characterized to understand the mechanism by which these properties are improved. Results indicated that high yield could be attributed to the following: (1) enhanced intracellular synthesis, demonstrated by an increase in the activities of key enzymes, and (2) accelerated cross-membrane substrate uptake and product secretion, indicated by improved membrane fluidity and permeability. Temperature tolerance could be attributed to the overexpression of the investigated heat shock proteins and oxidative stress proteins.

The preparation and characterization of a novel sphingan WL from marine Sphingomonas sp. WG

“…The production of gellan gum was below 10 g/L produced by three different strains S. paucimobilis E2 (DSM 6314), NK 2000 and GS1 and the highest production reported was about 35.7 g/L by the strain S. paucimobilis ATCC 314617. The production of welan gum is usually 20 g/L8 and can reach 26 g/L910 by the mutation breeding of producing strain or the optimization of fermentation process, however, its yield is much lower than that of xanthan gum (about 35–45 g/L)1. Thus, high production of sphingans will be of great importance for their applications.…”

An efficient production of a novel carbohydrate polymer Sphingan WL

“…The low production of sphingans generally limits their application. Therefore, multiple methods, such as the construction of highly productive strains and the optimization of culture conditions, have been applied to enhance their production, and these have improved their production to varying degrees. As demonstrated in previous studies, welan gum production is generally between 20 and 30 g L −1 , and the maxim production reported of approximately 41 g L −1 was obtained with Alcaligenes sp.…”

Construction of a Robust Sphingomonas sp. Strain for Welan Gum Production via the Expression of Global Transcriptional Regulator IrrE

“…is a promising producer of gellan gum polysaccharide, such as gellan gum, welan gum, rhamsan gum, and so on. Welan gum is an important member of gellan gum family that is widely used in food, medicine, concrete additives, and oil recovery because of its high and stable viscosity in aqueous solution over a broad range of temperature and pH (Zhu et al, 2014a;Ai et al, 2015;Liu et al, 2017). However, many restrictive factors in gellan gum polysaccharide production limit its yield and large-scale application.…”

“…strain. For welan gum production, heat from mechanical agitation and microbial metabolism (Zhu et al, 2014a), high viscosity and weak acidity from welan gum accumulation (Li et al, 2011a), and pigment from carotenoid synthesis (Zhang et al, 2016) result in the large demand of cooling water, alkali binding agent, strong ventilation or agitation for fermentation, and alcohol for polysaccharide purification, thereby causing high energy consumption and cost.…”

“…For the past few years, mutation breeding, adaptive laboratory evolution, and resequencing experiments have been used to obtain advanced industrial strains (Barrick and Lenski, 2013). Zhu et al (2014a) obtained a mutant S. sp. by atmospheric and room-temperature plasma-induced mutation, and the mutant could grow well at 37 • C. Nevertheless, these approaches have difficult in mutation direction grasping, beneficial combinatorial landscape occurrence, target strain screening, and good traits passing on (Blooma and Arnoldb, 2009).…”