444 research outputs found
Valorization of Purple Phototrophic Bacteria Biomass Resulting from Photo Fermentation Aimed at Biohydrogen Production
No full textThis study evaluated the feasibility of contextually producing hydrogen, microbial proteins, and polyhydroxybutyrate (PHB) using a mixed culture of purple phototrophic bacteria biomass under photo fermentative conditions. To this end, three consecutive batch tests were conducted to analyze the biomass growth curve and to explore the potential for optimizing the production process. Experimental findings indicated that inoculating reactors with microorganisms from the exponential growth phase reduced the duration of the process. Furthermore, the most effective approach for simultaneous hydrogen production and the valorization of microbial biomass was found when conducting the process during the exponential growth phase of the biomass. At this stage, achieved after 3 days of fermentation, the productivities of hydrogen, PHB, and microbial proteins were measured at 63.63 L/m3 d, 0.049 kg/m3 d, and 0.045 kg/m3 d, respectively. The biomass composition comprised a total intracellular compound percentage of 56%, with 27% representing PHB and 29% representing proteins. Under these conditions, the estimated daily revenue was maximized, amounting to 0.6 $/m3 d
Photo-fermentative hydrogen production from cheese whey: engineering of a mixed culture process in a semi-continuous, tubular photo-bioreactor
No full textThis work approaches the engineering of photo fermentative hydrogen production from cheese whey, for the scale-up of photo-bioreactors. Firstly, a brief review has been performed to identify the optimal reactor configuration as well as the main literature lacks. Results of the review analysis suggest that tubular photobioreactors are effective for the photo fermentation process. On the other hand, one of the main drawbacks to the scale-up of the proposed systems is the wide use of pure cultures, which requires aseptic environments and carefully controlled conditions. Based on the critical evaluation of the state of the art, a semi-continuous tubular photobioreactor, performing mixed culture hydrogen production from cheese whey, under unsterile conditions, was started up. Due to the lack of studies in this field, the case study was developed to provide a methodology for the reactor start-up, which represents the most critical phase of its operation. Preliminary tests were performed to choose the optimal operating conditions. To assess the effectiveness of cheese whey, results were compared to those obtained from a glucose based synthetic substrate, under steady state conditions. Experimental outcomes showed that the optimal Hydraulic Retention Time was 2 days and the most appropriate recirculation/pumping system consisted of an intermittent peristaltic pump. The semi-continuous feeding of cheese whey resulted in 87 mL/L d of hydrogen, which was similar to the productivity obtained under glucose feeding. The characterization of the residual organic content further indicated the possible accumulation of polyhydroxyalcanohates, which was estimated to constitute about the 40% of the total residual COD. These results further addressed the identification of key points to be better investigated to promote the effective photo fermentation scale-up for cheese whey valorization, such as the enhancement of the illumination conditions as well as the search for strategies to improve the uniform exposure of microbial cells to light
Repeated-Batch Fermentation of Cheese Whey for Semi-Continuous Lactic Acid Production Using Mixed Cultures at Uncontrolled pH
No full textThe paper investigates mixed-culture lactate (LA) fermentation of cheese whey (CW) in order to verify the possibility of using waste materials as feedstock to produce a product with high economic potential. The fermentation performance of two reactors operating in repeated-batch mode under uncontrolled pH conditions and various hydraulic retention time and feeding conditions was evaluated in terms of LA production. Five experimental phases were conducted. The hydraulic retention time (HRT) was varied from 1 to 4 days to verify its effect on the process performance. The best results, corresponding to the maximum LA concentration (20.1 g LA/L) and the maximum LA yield (0.37 g chemical oxygen demand (COD)(LA)/g COD(CW)), were reached by feeding the reactors with cheese whey alone and setting the HRT to 2 days. The maximum productivity of lactic acid (10.6 g LA/L/day) was observed when the HRT was decreased to 1 day
Implementing a sustainable process for the recovery of palladium from spent catalysts at industrial scale: A LCA approach
No full textDue to its unique physicochemical properties, palladium is widely used in several industry applications (e.g., vehicle emission control). In view of the circular economy, it is essential to explore secondary sources of palladium, such as urban mines. Current technologies for effective palladium recovery involve high energy consumption and severe environmental impact. More recently, a novel green method for recovering palladium from spent catalysts through a combination of mild acidic leaching and photodeposition on ZnO nanoparticles was proposed on a laboratory scale. In the present study, the environmental impacts of this recovery method, properly upscaled and modelled, was assessed by employing the LCA approach. Specifically, a comparative LCA was carried out for the process with as well as without recycling key components, such as Cu (II) and NaCl for the leaching solution and ZnO. The outcomes identified critical areas and drove the investigation of alternative process configurations to reduce its environmental footprint, such as the use of carbon dioxide in the photodeposition process with the aim of decreasing the resulting terrestrial ecotoxicity. This study marks a significant step forward in advancing research toward industrial−scale implementation of palladium recovery. It provides valuable insights for researchers in the field of green physicochemical processes for metal recovery, thus offering guidance for future decision−making towards more sustainable practices
Enhancing Dark Fermentative Hydrogen Production from Problematic Substrates via the Co-Fermentation Strategy
No full textThe aim of the present paper is the improvement of dark fermentative hydrogen production from problematic substrates. In detail, the study is aimed at (i) investigating the inhibiting effect of two problematic biomasses (i.e., of olive mill wastewater, containing recalcitrant/toxic compounds and cheese whey, lacking pH buffering capacity) on the dark fermentation process, (ii) as well as verifying the possibility to apply a co-fermentation strategy to enhance the process. To investigate the inhibiting effect of the substrates, two experimental sets were conducted using olive mill wastewater and cheese whey alone, under different food-to-microorganism ratios (i.e., 1, 2.5, and 5). Further experiments were conducted to verify the possibility of improving hydrogen production via the co-fermentation strategy. Such experiments included two tests conducted using different volumetric percentages of olive mill wastewater and cheese whey (90% olive mill wastewater + 10% cheese whey and 80% olive mill wastewater + 20% cheese whey). Results show that using olive mill wastewater alone, the inhibiting effect increased at a higher food-to-microorganism ratio. Moreover, because of the occurrence of a metabolic shift, hydrogen was not produced using 100% cheese whey. Interestingly, compared to the 100% olive mill wastewater condition, the use of 20% cheese whey allowed to double the hydrogen yield, reaching the high cumulative hydrogen production of 2.08 LL−1. Obtained results confirm that the two investigated substrates exert inhibiting effects on microorganisms. Nevertheless, co-fermentation is an effective strategy to improve the dark fermentation process of problematic biomass
Upcycling extraction residues from fruit waste bioactive compound recovery via fermentative and photofermentative hydrogen production
No full textThis study investigates the valorization of orange peel herbal dust (OPHD) and black elderberry press cake (BEPC), by-products of the food industry, through an integrated biorefinery approach. The process involved two main steps: the recovery of phenolic compounds using ultrasonic-assisted extraction and the subsequent production of hydrogen via dark fermentation (DF) and photofermentation (PF). Experimental results demonstrated that it is possible to efficiently recover phenolic compound (Extraction Yield = 22.33 ± 0.92 %, Total Phenolic Content = 24.08 ± 1.16 mg gallic acid/g dry weight from OPHD; Extraction Yield = 17.80 ± 0.41 %, Total Phenolic Content = 32.83 ± 2.24 mg gallic acid/g dry weight from BEPC) and that the extraction residues can be further valorized via biological routes. More specifically, OPHD exhibited hydrogen yields of 150.3 mL H2/g VS and 218.0 mL H2/g VS in DF and sequential DF-PF, respectively. A lower DF yield (20.5 mL H2/g VS) was obtained from BEPC, which provided better performance in single-stage PF. These findings contribute to advancing sustainable waste management practices and enhancing the economic viability of biorefinery processes in the food industry
A mechanistic mathematical model for photo fermentative hydrogen and polyhydroxybutyrate production
No full textAn original mathematical model describing the photo fermentation process is proposed. The model represents the first attempt to describe the photo fermentative hydrogen production and polyhydroxybutyrate accumulation, simultaneously. The mathematical model is derived from mass balance principles and consists of a system of ordinary differential equations describing the biomass growth, the nitrogen and the substrate degradation, the hydrogen and other catabolites production, and the polyhydroxybutyrate accumulation in photo fermentation systems. Moreover, the model takes into account important inhibiting phenomena, such as the self-shading and the substrate inhibition, which can occur during the evolution of the process. The calibration was performed using a real experimental data set and it was supported by the results of a sensitivity analysis study. The results showed that the most sensitive parameters for both hydrogen and PHB production were the hydrogen yield on substrate, the catabolites yield on substrate, and the biomass yield. Successively, a different experimental data set was used to validate the model. Performance indicators showed that the model could efficiently be used to simulate the photo fermentative hydrogen and polyhydroxybutyrate production by Rhodopseudomonas palustris. For instance, the index of agreement of 0.95 was observed for the validated hydrogen production trend. Moreover, the model well predicted the maximum PHB accumulation in bacterial cells. Indeed, the predicted and observed accumulated PHB were 4.5 and 4.8%, respectively. Further numerical simulations demonstrated the model consistency in describing process inhibiting phenomena. Numerical simulations showed that the acetate and nitrogen inhibition phenomena take place when concentrations are higher than 12.44 g L-1 and lower than 4.76 mg L-1, respectively. Finally, the potential long term hydrogen production from accumulated polyhydroxybutyrate in bacterial cells was studied via a fast-slow analysis technique
Fashion Culture: Power In Fashion with Stefano Tonchi and Grazia d'Annunzio
No full textStefano Tonchi, global chief creative officer for L’Officiel Group, and Grazia d’Annunzio, former deputy director of Vogue Italia, discuss the power of military uniforms and their influence on high fashion. Tonchi is co-author of the book "Uniform: Order and Disorder.
Wor(l)d-making Libraries: Fantastic Libraries as Creators of Alternative Realities
No full textFantasy fiction often appropriates the topos of the library to reflect upon the generative power of literature and on our ability to tap into it. Since the publication of Jorge Luis Borges’ influential short story, The Library of Babel (1941), the image of the library as a universe in itself, as a repository of virtually boundless (if unfathomable and labyrinthine) knowledge has become a recurring feature in fantasy literature. This essay seeks to investigate how British author Genevieve Cogman and American author Scott Hawkins refer to this tradition in their respective novels The Invisible Library (2014) and The Library at Mount Char (2015), through an analysis of some specific elements. In both texts, the structure of the library is represented as an interdimensional core, a macrocosm from which other dimensions may develop (including our own): each alternative reality hinges upon the library, which is in itself boundless, albeit rigorously arranged. While Cogman chooses to highlight the library’s function as a portal to other worlds, thus staging a traditional quest consistent with the informing paradigms of fantasy fiction, Hawkins stresses its metaphysical quality, reflecting upon the idea of God and its viability in our contemporary culture. Furthermore, these conceptions are equally associated with an understanding of language which enhances the tropes of words as “speaking” things into existence. Whether enchanting or emanating from the library’s ordering force, the verbal tools devised by Cogman and Hawkins revolve around the idea that language is power, and that through language reality can be reshaped
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