Production, purification, and antibiofilm activity of a novel exopolysaccharide from Arthrobacter sp. B4.

A novel exopolysaccharide (EPS), namely, B4-EPS, is produced by Arthrobacter sp. B4. Response surface methodology (RSM) was employed to optimize the fermentation medium for increasing B4-EPS production. Based on Plackett-Burman design (PBD), glucose, yeast extract, and KH2PO4 were selected as significant variables, which were further optimized by a central composite design (CCD). According to response surface and canonical analysis, the optimal medium was composed of 16.94 g/L glucose, 2.33 g/L yeast extract, and 5.32 g/L KH2PO4. Under this condition, the maximum yield of B4-EPS reached about 8.54 g/L after 72 hr of batch fermentation, which was pretty close to the predicted value (8.52 g/L). Furthermore, B4-EPS was refined by column chromatography. The main homogeneous fraction (B4-EPS1) was collected and applied to assay of antibiofilm activity. B4-EPS1 exhibited a dose-dependent inhibitory effect on biofilm formation of Pseudomonas aeruginosa PAO1 without antibacterial activity. About 86.1% of biofilm formation of P. aeruginosa PAO1 was inhibited in the presence of 50 µg/mL B4-EPS1, which was more effective than the peer published data. Moreover, B4-EPS1 could prevent biofilm formation of other strains. These data suggest B4-EPS may represent a promising strategy to combat bacterial biofilms in the future.

Characterization and flocculation mechanism of an alkali-activated polysaccharide flocculant from Arthrobacter sp. B4.

The characterization and flocculation mechanism of a bioflocculant produced by Arthrobacter sp. B4 were investigated. The bioflocculant's active ingredient was a polysaccharide (B4-PS) that consisted of three main fractions corresponding to the molecular weights of approximately 3.97×10(4)Da, 6.84×10(3)Da and 5.9×10(6)Da, respectively. These fractions were composed of galactose, glucose, mannose and glucuronic acid. Flocculation experiments showed that B4-PS could spontaneously flocculate in the presence of Ca(2+) ions at a high pH (>12.0), followed by the pH reduction to ∼6.0. The self-flocculation of B4-PS may be mediated by ionization and charge neutralization mechanism. Furthermore, B4-PS exhibited excellent capabilities for pollutant removal and pH reduction in alkaline wastewater. These data suggest B4-PS may be a promising tool for use in industrial alkaline wastewater pretreatment.