Systematic investigation of simultaneous copper biosorption and nitrogen removal from wastewater by an aerobic denitrifying bacterium of auto-aggregation.

Finding effective methods for simultaneous removal of eutrophic nutrients and heavy metals has attracted increasing concerns for the environmental remediation. Herein, a novel auto-aggregating aerobic denitrifying strain (Aeromonas veronii YL-41) was isolated with capacities for copper tolerance and biosorption. The denitrification efficiency and nitrogen removal pathway of the strain were investigated by nitrogen balance analysis and amplification of key denitrification functional genes. Moreover, the changes in the auto-aggregation properties of the strain caused by extracellular polymeric substances (EPS) production were focused on. The biosorption capacity and mechanisms of copper tolerance during denitrification were further explored by measuring changes in copper tolerance and adsorption indices, as well as by variations in extracellular functional groups. The strain showed extremely strong total nitrogen removal ability, with 67.5%, 82.08% and 78.48% of total nitrogen removal when NH4+-N, NO2--N, and NO3--N were used as the only initial nitrogen source, respectively. The successful amplification of napA, nirK, norR, and nosZ genes further demonstrated that the strain accomplished nitrate removal through a complete aerobic denitrification pathway. The production of protein-rich EPS of up to 23.31 mg/g and an auto-aggregation index of up to 76.42% may confer a strong biofilm-forming potential to the strain. Under the stress of 20 mg/L copper ions, the removal of nitrate-nitrogen was still as high as 71.4%. In addition, the strain could achieve an efficient removal of 96.9% of copper ions at an initial concentration of 80 mg/L. Scanning electron microscopy and deconvolution analysis of characteristic peaks confirmed that the strains encapsulate heavy metals by secreting EPS and, meanwhile, form strong hydrogen bonding structures to enhance intermolecular forces to resist copper ion stress. This study provides an innovative and effective biological approach for the synergistic bioaugmentation removal of eutrophic substances and heavy metals from aquatic environments.

Research on contents of anthraquinones in Cassiae Semen by principal component analysis.

Cassiae Semen is a common traditional Chinese medicine, and contents of anthraquinones of Cassiae Semen different significantly from area to area. According to Chinese Pharmacopoeia (2010 edition), only contents of aurantio obtusin and chrysophanol were used to evaluate the quality of Cassiae Semen, another data could be added later. Ten batches of Cassiae Semen from different areas were determined, and total anthraquinones, total free anthraquinones and total combined anthraquinones contents were assessed by ultraviolet visible spectrophotometer, contents of aurantio obtusin, rhein, aloe emodin, emodin, chrysophanol and physcion were determined by HPLC. After that, principal components analysis was used to evaluate these data determined previous by dimension reduction analysis. At last, the result suggests that three main components were found out, it shows that content of aloe emodin could be used to evaluate the quality of Cassiae Semen as well as contents of aurantio obtusin and chrysophanol. And Cassiae Semen from Hebei province posseses higher quality than Cassiae Semen from other different areas. All these results can provide a good reference for quality evaluating of Cassiae Semen medicinal materials at a certain extent.