Abstract
Welan gum, a kind of microbial exopolysaccharides, produced by the genus Sphingomonas, have great potential for application in many fields, such as the food industry, cement production, and enhanced oil recovery. But there are still challenges to reduce the cost, enhance the production and the quality. Herein, the bioinformatics analysis of WelR gene was preformed, and the characterization and function of WelR, welan gum lyase, from Sphingomonas sp. WG were investigated for the first time. The results indicated that 382nd (Asn), 383rd (Met), 494th (Asn), and 568th (Glu) were the key amino acid residues, and C-terminal amino acids were essential to keeping the stability of WelR. The optimal temperature and pH of the enzymatic activity were found to be 25°C and 7.4, respectively. And WelR was good low temperature resistance and alkali resistant. K+, Mg2+, Ca2+, Mn2+, and EDTA increased WelR activities, in contrast to Zn2+. Coupled with the change in glucose concentration and growth profile, the qRT-PCR results indicated that WelR may degrade welan gum existing in the culture to maintain bacterial metabolism when glucose was depleted. This work will lay a theoretical foundation to establish new strategies for the regulation of welan gum biosynthesis.
Highlights
Sphingans, produced by the genus Sphingomonas, were important microbial exopolysaccharides (EPs), including gellan (S-60), welan (S-130), diutan (S-657), rhamsan (S-194), and so on
Welan gum consisting of neutral sugars, glucuronic acid, and some O-acyl groups exhibits excellent and attractive properties, such as pseudoplasticity, suspensibility, thickening property (Jansson et al, 1985; Xu et al, 2013; Li et al, 2016b)
WG was deposited in the China Center for Type Culture Collection (CCTCC) under the number M2013161
Summary
Sphingans, produced by the genus Sphingomonas, were important microbial exopolysaccharides (EPs), including gellan (S-60), welan (S-130), diutan (S-657), rhamsan (S-194), and so on. The β-eliminative cleavage enzyme has been widely described for application in food technology, therapeutic tools, polysaccharide structure analysis, protoplasts formation, oligosaccharide production, and especially control of polysaccharide rheological properties (Boyd et al, 1993; Hatch and Schiller, 1998; Michaud et al, 2003). In consideration of the associated polysaccharides structural regulation mechanism, the investigation on the function of welan gum lyase may provide new insights into the fermentation strategies of welan gum production. To further study the effects of the C-terminus on WelR structure, and C-terminal 72 amino acids truncated enzyme (named WelRC72) was constructed by gene cloning. WG, which will provide a theoretical basis for establishing new strategies to regulate welan gum biosynthesis
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