Enhanced biomass production and wastewater treatment in attached co-culture of Chlorella pyrenoidosa with nitrogen-fixing bacteria Azotobacter beijerinckii.

Algae-bacteria symbiosis can promote the growth of microalgae and improve the efficiency of wastewater treatment. Attached culture is an efficient culture technique for microalgae, with benefits of high yield, low water consumption and easy harvesting. However, the promoting effects of bacteria on microalgae in attached culture are still unclear. In this study, different forms of a nitrogen-fixing bacteria, Azotobacter beijerinckii (including bacteria supernatant, live bacteria, and broken bacteria), were co-cultured with Chlorella pyrenoidosa in an attached culture system using wastewater as the culture medium. The results showed that the broken A. beijerinckii form had the best growth promotion effect on C. pyrenoidosa. Compared with the pure algae culture, the biomass of C. pyrenoidosa increased by 71.8% and the protein increased by 28.2%. The live bacteria form had the best effect on improving the efficiency of wastewater treatment by C. pyrenoidosa, with the COD, PO43- and NH4+-N removal rates increased by 20.8%, 18.5% and 8.9%, respectively, in comparison with the pure algae culture. The attached co-culture mode promoted the growth of C. pyrenodisa better than the suspended co-culture mode. This research offers a new way for improving microalgae biomass and wastewater treatment by attached algae-bacteria symbiont.

Protective Role of Somatostatin in Sepsis-Induced Intestinal Barrier Dysfunction through Inhibiting the Activation of NF-κB Pathway.

Somatostatin (SST) has a protective role in intestinal injury, inflammatory response, and intestinal mucosal barrier in rats with acute pancreatitis. However, its function in sepsis-induced intestinal barrier dysfunction remains largely unknown. A mouse sepsis model was constructed, and SST was injected into the tail vein. Then, hematoxylin and eosin staining (HE) was used to detect the intestinal barrier dysfunction. Enzyme-linked immunosorbent assay was used to detect the level of tumor necrosis factor α- (TNF-) α, interleukin- (IL-) 6, and interleukin- (IL-) 10 in the ileum. Expressions of tight junction proteins, zonula occludens- (ZO-) 1 and Claudin-1, and NF-κB p65 in the ileum were detected using western blot and immunohistochemistry as needed. Furthermore, JSH-23 as an inhibitor of the NF-κB pathway was injected into sepsis mice with SST or not. Mice with sepsis showed an obvious intestinal barrier dysfunction with decreasing specific somatostatin receptor subtype (SSTRs), and increasing TNF-α, IL-6, and IL-10 in the ileum. SST could relieve the injury, the decrease of SSTRs, and the increase of TNF-α and IL-6 induced by sepsis and also further enhanced the expression of IL-10. Further analysis showed that ZO-1 and Claudin-1 were reduced in the ileum by sepsis but enhanced by SST. NF-κB p65 was promoted in the ileum by sepsis but inhibited by SST. Further experiments confirmed that NF-κB inhibitor JSH-23 could repair the intestinal barrier dysfunction and enhance the protective effect of SST on the intestinal barrier. SST, with a protective effect on intestinal barrier dysfunction through suppression of NF-κB, could be a potential therapeutic drug for sepsis-induced intestinal barrier dysfunction.

Microwave assisted flocculation for harvesting of Chlorella vulgaris.

Microalgae harvesting is a major hindrance for the development of the microalgae industry. In this paper, short microwave treatment was used to assist the flocculation of Chlorella vulgaris with three flocculants, Fe3+ (FeCl3), chitosan, and Ca2+ (CaCl2). A microwave irradiation time of 20 s, and a pH of 10 was found to be the optimum condition. The harvesting efficiency could be significantly increased by 43.2%, 49.5% and 39.6%, respectively for Fe3+, chitosan, and Ca2+ assisted by microwave under these conditions. Microwave treatment did not cause any damage to the algal cells, and had no obvious influence on the lipid extraction. Microwave treatment decreased the concentration of the flocculants in culture medium after flocculation; this treatment enabled the reuse of the supernatant. This study provides a new and promising method of improving the flocculation efficiency for microalgae harvesting, by using microwave energy.

[Spatial and temporal variation of Fe and Mn in the stormwater wetland].

To study the purification mechanism and biogeochemical cycle of wetlands, the concentration of Fe/Mn and oxidation reduction potential (ORP) in the pore water were monitored in situ on the Wuhan Zoo stormwater wetland from 2004 to 2006. The results showed that the water level of the wetland was changed from -10 cm to 30 cm, and the range of ORP was-120-220 mV. The elements of sulfur, iron and manganese were the main oxidation and reduction systems in the wetland. The ranges of total Fe, Mn and Fe2+ concentration were 0.60-2.35, 0.75-1.89 and 0.20-1.25 mg x L(-1), respectively. The concentrations of total Fe, Mn and Fe2+ were higher in spring and summer than that in autumn and winter, while the sulfate concentration was on the contrary and the ratio of Fe2+/Fe was slightly various in different seasons. From the surface of 10 cm to 50 cm underground, ORP and pH was decreased, whereas the concentrations of total Fe, Mn and Fe2+ were increased (except for the surface water). Through the correlation analysis, it was showed that the correlation of ORP and total Mn and Fe2+ was negative and significant, while there was no significant correlation between ORP and total Fe (R = -0.169, p < 0.0001). The order of the correlation coefficient was total Mn, Fe and Fe2+ in turn. Therefore, the systems of sulfur, iron and manganese were the important component of the oxidation and reduction system for stormwater wetland.