[Effect of S-adenosylmethionine on vascular smooth cells proliferation and migration].

OBJECTIVE: To investigate the effect of S-adenosyl-L-methionine (SAMe) on vascular smooth muscle cells (VSMCs) proliferation and migration and neointima formation in rat carotid artery balloon injury model. METHODS: Rat VSMCs were divided into control group, TNF-α (10 ng/ml) group, SAMe (0.2 mmol/L) group and TNF-α + SAMe group. VSMC migration distance and proliferation were examined by cell scrape tests and MTT method. NF-κB activity was analyzed by EMSA. PDGF mRNA expression was detected by Northern blot. SD rat were divided into control group, carotid balloon injury group treated with saline or SAMe (15 mg×kg(-1)×d(-1) for 14 d), then blood vessel proliferation was observed histologically in rat carotid artery. RESULTS: (1) In vitro, the VSMCs migration distance, absorbance at 490 nm, PDGF mRNA expression, NF-κB activity were all increased in TNF-α group compared to the control group (P < 0.01), and decreased in TNF-α + SAMe group compared to the TNF-α group (P < 0.01). (2) In the balloon injury in vivo models, the intima area of saline group and SAMe group was increased compared to the control group, while the lumen area was larger and the intima area was smaller in the SAMe group than in the saline group (all P < 0.05). CONCLUSION: SAMe could reduce TNF-α induced VSMC proliferation and migration possibly through inhibiting NF-κB activity and downregulating PDGF gene expression.

Construction and application of a Xanthomonas campestris CGMCC15155 strain that produces white xanthan gum.

In the industrial production of xanthan gum using Xanthomonas campestris CGMCC15155, large amounts of ethanol are required to extract xanthan gum from the fermentation broth and remove xanthomonadin impurities. To reduce the amount of ethanol and the overall production cost of xanthan gum, a xanthomonadin-deficient strain of CGMCC15155 was constructed by inserting the Vitreoscilla globin (vgb) gene, under the control of the LacZ promoter, into the region of the pigA gene, which is involved in xanthomonadin synthesis. The insertion of vgb inactivated pigA, resulting in the production of white xanthan gum. The lack of xanthomonadins resulted in a decreased yield of xanthan gum. However, the expression product of vgb gene, VHb, could increase the metabolism of X. campestris, which allowed the production of xanthan gum to reach wild-type levels in the engineered strain. The yield, molecular weight, and rheological properties of the xanthan gum synthesized by the engineered and wild-type bacteria were essentially the same. When the same volume of ethanol was used, the whiteness values of the xanthan gum extracted from engineered and wild-type bacteria were 65.20 and 38.17, respectively. To extract xanthan gum with the same whiteness, three and seven times the fermentation volume of ethanol was required for the engineered and wild-type strains, respectively. Thus, the engineered train reduced the requirement for ethanol in xanthan gum production by 133.3%. The results demonstrated that the engineered bacteria used less ethanol, thus reducing the downstream processing cost in xanthan gum production.

Tailor-made polysaccharides containing uniformly distributed repeating units based on the xanthan gum skeleton.

Xanthan gum, whose structure determines its physicochemical properties, is an important microbial polysaccharide. Currently, marketed xanthan products are produced by wild-type strains followed by post-fermentation separation or chemical modification, which are complicated and labor-intensive. In the present study, we designed eight polysaccharides containing uniformly distributed repeating units and different rheological properties based on natural xanthan skeleton and according to the relationship between property and structure. The customized polysaccharides were produced in Xanthomonas campestris CGMCC 15155 using marker-less gene knockout and gene overexpression methods. The results showed that their different homogeneous primary structures determined their specific secondary structures and rheological properties, especially the terminal mannose, the pyruvyl group, and the acetyl group attached to the internal mannose of the side chain. Polysaccharides lacking a terminal mannose, such as xanthan XdM-0 and XdM-A, had reduced zero-shear viscosity and modulus values. The internal acetyl group of the side chain stabilized the helix structure (e.g., in XG-A0), while the pyruvate group had the opposite effect (e.g., in XG-AP and XG-0P). The eight xanthan variants provide a promising theoretical foundation to further study the structure-activity relationship of xanthan and will help to construct xanthan-containing block copolymers.

Enhancement of transparent hydrogel sanxan production in Sphingomonas sanxanigenens NX02 via rational and random gene manipulation.

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 ±â€¯0.83 g/L to 21.20 ±â€¯0.38 g/L in a 5 L bioreactor, while the cell dry weight (CDW) was decreased from 9.61 ±â€¯0.14 g/L to 3.12 ±â€¯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.

Network structure and functional properties of transparent hydrogel sanxan produced by Sphingomonas sanxanigenens NX02.

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 Ca2+. 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.