Production, characterization and antibacterial activity of exopolysaccharide from a newly isolated Weissella cibaria under sucrose effect.

Weissella cibaria 27 (W27) is a new lactic acid bacterium which has been screened from kimchi, and is important in diary fermentation. This is first-attempt to understand the effects of sucrose and achieve the highest exopolysaccharide (EPS) productivity from W27. The metabolic compounds of lactic acid, acetic acid and ethanol are at similar levels when the cultures with glucose or lactose; except for EPS is significantly increased up to 24.8 g/L with 60 g/L of sucrose. Scanning electron microscopy (SEM) results reveal cell length changing shorter after sucrose addition. By Taguchi's approach, an L9 orthogonal array was adopted to evaluate the effects of culture were ranked according to the EPS production as temperature > time > initial pH, in which optimal conditions were at 22°C and pH 6.2 for 24 h. The major composition of EPS is dextran of α-1,6 glycosidic linkage with molecular weight of 1.2 x 107 Da by nuclear magnetic resonance (NMR) and high-performance size-exclusion chromatography (HPSEC) analysis. The surface property of W27 induced by sucrose is become more hydrophobic to better inhibit bacteria. The simple cultural approach for this new dextran producing strain, W27, has potential in the food, feed, antibacterial agent, and cosmetic industry.

Identification of Gold Sensing Peptide by Integrative Proteomics and a Bacterial Two-Component System.

The proteomics strategy was utilized to analyze and identify the gold adsorption proteins from Tepidimonas fonticaldi AT-A2, due to its outstanding performance in gold-binding and recovery. The results showed that three small proteins, including histidine biosynthesis protein (HisIE), iron donor protein (CyaY) and hypothetical protein_65aa, have a higher ability to adsorb gold ions because of the negatively charged domains or metal binding sites. On the other hand, the Salmonella PmrA/PmrB two-component system first replaces the iron (III)-binding motif using the peptide sequence from hypothetical protein_65aa, and this is then used to reveal the sensing and responsiveness to gold metal ions, which is totally different from the performance of traditional gold binding peptide (GBP) on the crystals on the surface of gold (111). We have successfully demonstrated an integrative proteomics and bacterial two-component system to explore the novel GBP. Finally, the heterologous over-expression of GBP by E. coli and the equilibrium of binding capacity for Au(III) have been conducted.

[Vertical Variation of Phosphorus Forms in Lake Dianchi and Contribution to Release].

Columnar sediment samples were collected from the Waihai of Lake Dianchi in northern, central and southern sediment, combined with the data of phosphorus in the overlying water and sediment organic matter, the effects of organic matter and particle size on sediment release were studied, and the influence of different forms of phosphorus release from sediments and their contributions were discussed. The results showed:Sediment pore water ρ(DTP) and ρ(SRP) was negatively correlated with contents of OM, clay (<4.00 µm) and silt (4.00-63.00 µm), but it showed a significant positive correlation with sand (>63.00 µm) content. Theincrease in organic matter content of the sediments significantly reduced the gap water phosphorus mass concentration, and increasing clay and silt contents reduced the gap water phosphorus mass concentration, inhibiting the release of phosphorus in sediments. Potentially mobile phosphorus of the Lake Dianchi sediment was significantly positively correlated with the clay and silt contents, and was significantly negatively correlated with the sand content. It was indicated that clay and silt may enhance the phosphorus movement ability of the sediment, and the sand may enhance the retention of phosphorus in the sediment. In a short time scale, phosphorus of sediment was released mainly in northern Waihai, staying mainly in central and southern; in a longer time scale, phosphorus of sediment was released mainly in northern and central Waihai, staying mainly in southern. Control of phosphorus release from sediments in Lake Dianchi should take into account the effects of different forms of phosphorus, organic matter and particle size, and take corresponding measures to control the release of phosphorus in sediments of northern Dianchi mainly.