Coupling Mixed Culture Fermentation and Photo fermentation for Bio H2 Recovery: Preliminary Assessment of the Fermentation Yields and PNSB Growth on Fermentative Broth

Hydrogen has been widely recognized as a promising tool to address global warming problems, due to its high energy density and the sustainability of its utilization. Among the possible methods for its production, the biological processes have gained a lot of interest in recent years, as they would allow for an alternative and environment-friendly production. In this preliminary study, a two-stage co-fermentation/photo-fermentation process has been investigated. The first stage focused on the production of a medium enriched in volatile fatty acids (VFAs) to be used as a substrate for Purple Non-Sulphur Bacteria (PNSB). The co-fermentation of an organic waste mixture and sewage has been investigated, evaluating the VFAs production yields at different organic loadings (0, 5, 10, 15, 20, 25 kgTVS(mixture) m-3 ). The highest VFA production yields (410.0 and 381.1 gVFA(COD) kgTVS-1 ) were obtained at 10 and 15 kgTVS(mixture) m-3 , respectively. Two PNSB strains, Rhodopseudomonas palustris and Rhodospirillum rubrum, were fed with the fermentation broth, and compared in terms of biomass production. Despite no significant hydrogen production being observed, both strains showed a consistent boost in growth yields when fed with the fermentative broth rather than with the standard growth medium (a two-fold higher biomass production for Rps. palustris, and eight-fold higher for Rsp. rubrum). This suggests how the use of fermentative effluents as a culture medium for PNSB cultivation is a viable option to foster their growth. However, the limited hydrogen production in all the tested conditions is in disagreement with the literature evidence and certainly requires further investigation to detect any possible cause of inhibition

Antioxidant Activity of Supercritical CO2 Extracts of Helichrysum italicum

The antioxidant activity of supercritical CO 2 extracts of H. italicum dried flower heads derived from the commercial drug and from plants grown in different areas of north-east Italy with different culturing conditions was determined. In particular, the characterization of the antioxidant activity was made by the DPPH and s-carotene bleaching test methods. The four kind of H. italicum extracts were also tested for their ability to scavenger superoxide radicals. All extracts showed, although with different importance, an antioxidant activity with all the methods performed. The supercritical extracts obtained from commercial dried H. italicum flower heads and from dried flower heads belonging to wild plants exhibited the highest activity. These results established H. italicum supercritical extracts as important antioxidant solvent-free matrices in alimentary (i.e., dietary, nutraceutical, flavouring) and cosmetic fields, as well as the value of coastal Mediterranean areas to serve as an exploitable source ..

Coupling Mixed Culture Fermentation and Photo fermentation for Bio H2 Recovery: Preliminary Assessment of the Fermentation Yields and PNSB Growth on Fermentative Broth

Hydrogen has been widely recognized as a promising tool to address global warming problems, due to its high energy density and the sustainability of its utilization. Among the possible methods for its production, the biological processes have gained a lot of interest in recent years, as they would allow for an alternative and environment-friendly production. In this preliminary study, a two-stage co-fermentation/photo-fermentation process has been investigated. The first stage focused on the production of a medium enriched in volatile fatty acids (VFAs) to be used as a substrate for Purple Non-Sulphur Bacteria (PNSB). The co-fermentation of an organic waste mixture and sewage has been investigated, evaluating the VFAs production yields at different organic loadings (0, 5, 10, 15, 20, 25 kgTVS(mixture) m-3). The highest VFA production yields (410.0 and 381.1 gVFA(COD) kgTVS-1) were obtained at 10 and 15 kgTVS(mixture) m-3, respectively. Two PNSB strains, Rhodopseudomonas palustris and Rhodospirillum rubrum, were fed with the fermentation broth, and compared in terms of biomass production. Despite no significant hydrogen production being observed, both strains showed a consistent boost in growth yields when fed with the fermentative broth rather than with the standard growth medium (a two-fold higher biomass production for Rps. palustris, and eight fold higher for Rsp. rubrum). This suggests how the use of fermentative effluents as a culture medium for PNSB cultivation is a viable option to foster their growth. However, the limited hydrogen production in all the tested conditions is in disagreement with the literature evidence and certainly requires further investigation to detect any possible cause of inhibition

Hydrodynamic Cavitation for Pollutant Treatment in the New Horizon of Green Chemistry

The study describes a systematic numerical optimization of a Venturi tube for wastewater treatment under cavitation conditions. The numerical approach employs computational fluid dynamics methodologies in a Reynolds-Averaged Navier-Stokes framework combined with an optimization algorithm to enhance a baseline Venturi geometry. A robust meshing technique is provided in order to define the numerical model associated with the baseline solution. The process compares alternative mesh sizes and turbulence closure to discover the optimal accuracy and processing time balance. Then the model is used as a starting point for the optimization. An optimal configuration is found to be able to improve the tube mean vapor quality by around 130% compared to the starting geometry

Microbial Community of the Acidogenic Fermentation of Urban Waste: Effect of the Hydrodynamic Cavitation Pre-treatment

International audiencePurpose This study aims at understanding how the acidogenic fermentation microbial community was impacted by the hydrodynamic cavitation (HC) pre-treatment of the substrates' mixture, constituted by waste-activated sludge and vegetable waste 1:1 on a TVS basis.Methods HC was performed with power = 8 kW, P = 1.4-1.5 bar, Q(mixture) of 25-30 L/min, 1550-1650 rpm, duration: 30 min. Fermentation tests were conducted on cavitated (CAV) and not cavitated (NCAV) mixture at T = 37 degrees C inside 4 L reactors in batch mode, then switched to semi-continuous with an OLR of 8 kg(TVS) m(-3) d(-1). Microbial community was characterized by 16S rRNA sequencing at the beginning and end of the pseudo-steady-state. Ecological diversity and clustering among the samples were determined by beta diversity, Venn diagram, and non-metric multi-dimensional scaling (NMDS) analysis.Results Cavitation was efficient in substrates' hydrolyzation but resulted in a lower microbial diversity of 3.85 (Shannon Index) and VFAs concentration of 12.9 gCOD(VFA) L-1 in the anaerobically fermented cavitated mixture (AF-CAV), respect to 4.54 and 18.2 gCOD(VFA) L-1 in the anaerobically fermented not cavitated mixture (AF-NCAV), respectively. NMDS analysis showed that AF-CAV and AF-NCAV samples formed two different clusters, with VFAs concentration as the only significant factor explaining their difference (R-2 = 1, Pr > r = 0.04167). Functional redundancy among community members probably allowed to maintain a stable VFAs composition despite the microbial community variation observed at the end of the test.Conclusion The insights here provided on the effects of HC confirm the fundamental role played by microbial community in acidogenic fermentation processes and underline its importance in evaluating the effect of substrates' pre-treatment