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Polymer sanxan is a novel microbial polysaccharide produced by Sphingomonas sanxanigenens NX02, which can produce poly-3-hydroxybutyrate (PHB) simultaneously. A strategy of combining rational and random gene manipulation was investigated to improve the yield of sanxan. Several crucial PHB biosynthesis genes were deleted through homologous recombination, then the PHB-deficient mutant was treated with plasma mutagenesis to obtain NXdP, an engineering strain. Ultimately, the yield of purified sanxan produced by strain NXdP increased from 14.88 ± 0.83 g/L to 21.20 ± 0.38 g/L in a 5 L bioreactor, while the cell dry weight (CDW) was decreased from 9.61 ± 0.14 g/L to 3.12 ± 0.15 g/L. The total precipitable material (crude sanxan) produced from NXdP showed higher zero-shear viscosity, light transmittance, and greater gel strength than that from NX02 due to the enhancement of its purity. The engineering strategies explored here are useful for engineering cell factories to produce other valuable metabolites., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

The micro-network structure and functional properties of sanxan, a novel polysaccharide produced by Sphingomonas sanxanigenens NX02, were investigated. Transparent hydrogel sanxan was a high acyl polymer containing 8.96% acetyl and 4.75% glyceroyl. The micro-network structure of sanxan was mainly cyclic configurations composed of side-by-side intermolecular associations, with many rounded nodes found. Sanxan exhibited predominant gelation behavior at concentrations above 0.1%, which was enhanced by adding cations, especially Ca 2+ . The gel strength of sanxan was much higher than that of low acyl gellan, but slightly lower than that of high acyl gellan. Furthermore, the conformation transition temperature was increased in the presence of added cations. Moreover, sanxan showed excellent emulsifying and emulsion stabilizing properties. Consequently, such excellent functional properties make sanxan a good candidate as a gelling, stabilizing, emulsifying, or suspending agent in food and cosmetics industries, and in medical and pharmaceutical usage., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

Sphingomonas sanxanigenens, a new species of the genus Sphingomonas, synthesizes extracellular biopolymer termed sanxan. Sanxan polysaccharide was purified from the fermentation broth by Sephacryl S-400 column chromatography. The molecular weight of sanxan polysaccharide was 408kDa by the method of size-exclusion chromatography combined with laser light scattering. Based on FT-IR, periodate oxidation, Smith degradation, composition analysis and nuclear magnetic resonance experiments, the structure of sanxan polysaccharide was elucidated as follows: The solution of sanxan polysaccharide showed properties of high viscosity and shear-thinning. By cooling hot solutions, sanxan polysaccharide could form elastic thermoreversible gel., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

A universal method to enhance productivity and viscosity of bacterial exopolysaccharides was developed. The technique was based on the principle that ampicillin can inhibit the biosynthesis of peptidoglycan, which shares a common synthetic pathway with that of bacterial exopolysaccharides. Serial passages of three typical representatives of bacterial EPS-producing strains, namely Sphingomonas elodea, Xanthomonas campestris, and Paenibacillus elgii, were subjected to ampicillin, which was used as a stressor and a mutagen. These mutant strains are advantageous over other strains because of two major factors. First, all of the resulting strains were almost mutants with increase in EPS productivity and viscosity. Second, isolated serial strains showed different levels of increase in EPS production and viscosity to satisfy the different requirements of practical applications. No differences were observed in the monosaccharide composition produced by the mutant and parent strains; however, high-viscosity mutant strains exhibited higher molecular weights. The results confirmed that the developed method is a controlled universal one that can improve exopolysaccharides productivity and viscosity., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

The microbial exopolysaccharides are water-soluble polymers secreted by microorganisms during fermentation. The biopolymer gellan gum is a relatively recent addition to the family of microbial polysaccharides that is gaining much importance in food, pharmaceutical and chemical industries due to its novel properties. It is commercially produced by C.P. Kelco in Japan and the USA. This article presents a critical review of the available information on the gum synthesized by Sphingomonas paucimobilis with special emphasis on its fermentative production. Factors affecting the fermentative production of gellan gum and problems associated with mass transfer have been addressed. Classification and trade names of gellan gum has been specified. Characteristics of gellan gum with respect to its structure, physicochemical properties are discussed. An attempt has also been made to review the current and potential applications of gellan gum in food, pharmaceutical and other industries., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

Mild hydrolysis of Sphingomonas sp. ATCC 31555 polysaccharide WL-26 afforded a new oligosaccharide, F21. Structural resolution based on sugar and methylation analyses as well as NMR data revealed the oligosaccharide to have the following structure: [Formula, see text:]., (Copyright © 2012 Elsevier Ltd. All rights reserved.)