Algal wastewater treatment and biomass producing potential: nutrient removal efficiency and cell physiological responses

Microalgae are sun - light cell factories that convert carbon dioxide to biofuels, foods, feeds, and other bioproducts. The concept of microalgae cultivation as an integrated system in wastewater treatment has optimized the potential of the microalgae - based biofuel production. These microorganisms contains lipids, polysaccharides, proteins, pigments and other cell compounds, and their biomass can provide different kinds of biofuels such as biodiesel, biomethane and ethanol. The algal biomass application strongly depends on the cell composition and the production of biofuels appears to be economically convenient only in conjunction with wastewater treatment. The aim of this research thesis was to investigate a biological wastewater system on a laboratory scale growing a newly isolated freshwater microalgae, Desmodesmus communis, in effluents generated by a local wastewater reclamation facility in Cesena (Emilia Romagna, Italy) in batch and semi - continuous cultures. This work showed the potential utilization of this microorganism in an algae - based wastewater treatment; Desmodesmus communis had a great capacity to grow in the wastewater, competing with other microorganisms naturally present and adapting to various environmental conditions such as different irradiance levels and nutrient concentrations. The nutrient removal efficiency was characterized at different hydraulic retention times as well as the algal growth rate and biomass composition in terms of proteins, polysaccharides, total lipids and total fatty acids (TFAs) which are considered the substrate for biodiesel production. The biochemical analyses were coupled with the biomass elemental analysis which specified the amount of carbon and nitrogen in the algal biomass. Furthermore photosynthetic investigations were carried out to better correlate the environmental conditions with the physiology responses of the cells and consequently get more information to optimize the growth rate and the increase of TFAs and C/N ratio, cellular compounds and biomass parameter which are fundamental in the biomass energy recovery.

Molecular characterization of human CD4+ IL-10-producing regulatory cells

Previous studies in the group led to the identification of CD4+FOXP3- cells with regulatory functions in human blood that coproduce IL-10 and IFN-gamma. These cells do not belong to the Treg cell lineage since they are Foxp3- but they show some similarities with Th1 cells since they express CCR5, T-bet and produce high levels of IFN-gamma. Thus, they share relevant characteristics with both T regulatory type I cells (Tr1) and Th1 cells and we called them Th1-10 cells. In this study we presented a molecular characterization of Th1-10 cells that includes a gene expression and a microRNA profiling and performed functional studies to assess Th1-10 cells regulatory properties. We demonstrated that Th1-10 cells have a high regulatory potential being able to block the proliferation of activated CD4 naïve T cells to a similar extent as conventional Treg cells, and that this suppression capacity is at least partially mediated by secreted IL10. We showed also that Th1-10 cells are closely related to Th1 effector memory cells and express genes involved in cytotoxicity. In particular, they express the transcription factor EOMES and the cytotoxic effector molecules GZMA and GZMK, and they release cytotoxic granules upon stimulation. Moreover, we found that Eomes regulates cytotoxic functions in CD4+ T cells. We demonstrated that miR-92a, selectively downregulated in Th1-10 cells, directly targets the 3’UTR of EOMES.and this finding identifies miR-92a as a possible mediator of Th1-10 cytotoxicity. Th1-10 cells retain some proliferative capacity when sorted ex vivo and activated in vitro via their TCR, and this effect is markedly enhanced by IL-15, which also had a pro-survival effect on Th-10 cells. Thus, in contrast to conventional cytotoxic T cells, Th1-10 cells have cytotoxic and regulatory functions and are not terminally differentiated, since they retain proliferative capacity.