Optimization and characterization of polysaccharide-based bioflocculant produced by Paenibacillus elgii B69 and its application in wastewater treatment.

The optimization, purification and characterization of bioflocculant produced by Paenibacillus elgii B69 were investigated. The bioflocculant was an exopolysaccharide composed of glucose, glucuronic acid, mannose and xylose. The maximum bioflocculant production was about 25.63 g/L achieved with sucrose at 51.35 g/L, peptone at 6.78 g/L and yeast extract at 0.47 g/L optimized by response-surface methodology. In addition, a series of experiments was performed to investigate the flocculation activities towards kaolin clay, dyeing pigment, heavy metal ion, and real wastewater and the result indicated the new bioflocculant had high activities towards all the tested pollutions. These results showed its great potential for water pretreatment used in industry.

Evaluation of nutrient limitation in aquatic ecosystems with nitrogen fixing bacteria.

There has always been a great need for simple and accurate bioassays for evaluating nutrient limitation in aquatic ecosystems. Whereas organic carbon is usually considered to be the limiting nutrient for microbial growth in many aquatic ecosystems, there are, however, many water sources that are limited by phosphorus or nitrogen. A method named "nitrogen fixing bacterial growth potential" (NFBGP) test, which is based on pre-culturing of autochthonous (target) microorganisms was described. The method was applied to evaluate phosphorus or nitrogen nutrient limitation in lake and sewage water samples using an isolate of the nitrogen fixing bacterium, Azorhizobium sp. WS6. The results corresponded well to those from the traditional algal growth potential (AGP) test and the bacterial regrowth potential (BRP) test, suggesting that the NFBGP test is a useful supplementary method for evaluating the limiting nutrient, especially phosphorus, in an aquatic environment.