Influence of Added Nutrients and Substrate Concentration in Biohydrogen Production from Winery Wastewaters Coupled to Methane Production

Effect of the addition of an inorganic carbon source on the degradation of sotol vinasse by Rhodopseudomonastelluris

The difficulty of the microbial conversion process for the degradation of sotol vinasse due to its high acidity and organic load makes it an effluent with high potential for environmental contamination, therefore its treatment is of special interest. Calcium carbonate is found in great abundance and has the ability to act as a neutralizing agent, maintaining the alkalinity of the fermentation medium as well as, through its dissociation, releasing CO2 molecules that can be used by phototrophic CO2-fixing bacteria. This study evaluated the use of Rhodopseudomonas telluris (OR069658) for the degradation of vinasse in different concentrations of calcium carbonate (0, 2, 4, 6, 8 and 10% m/v). The results showed that calcium carbonate concentration influenced volatile fatty acids (VFA), alkalinity and pH, which in turn influenced changes in the degradation of chemical oxygen demand (COD), phenol and sulfate. Maximum COD and phenol degradation values of 83.16 ± 0.15% and 90.16 ± 0.30%, respectively, were obtained at a calcium carbonate concentration of 4%. At the same time, the lowest COD and phenol degradation values of 52.01 ± 0.38% and 68.21 ± 0.81%, respectively, were obtained at a calcium carbonate concentration of 0%. The data obtained also revealed to us that at high calcium carbonate concentrations of 6-10%, sotol vinasse can be biosynthesized by Rhodopseudomonas telluris (OR069658) to VFA, facilitating the degradation of sulfates. The findings of this study confirmed the potential for using Rhodopseudomonas telluris (OR069658) at a calcium carbonate concentration of 4% as an appropriate alternative treatment for sotol vinasse degradation.

Experimental evaluation of temperature, nutrients, and initial concentration on medium-chain carboxylic acids production from winery wastes

In the wine industry, grape processing is accompanied by waste generation, such as grape stalks, winery wastewater, and grape pomace (GP). GP can be used to produce value-added compounds such as medium-chain carboxylic acids (MCCA). This work aimed to determine the operational conditions (temperature, addition of nutrients, and initial waste concentration) to improve MCCA production using waste GP from the winery industry as a substrate. The electron donor (ethanol) and electron acceptor (acetate) were directly generated from the GP and consecutively used to produce MCCA. The treatment with high concentration, temperature, and nutrient addition promotes caproic acid's maximal yield and concentration (0.11 ± 0.02 g MCCA/g TS). Nutrients' presence and temperature significantly affected electron acceptor production. The addition of nutrients and 30 °C leads to elevated acetate production. However, at 37 °C, butyrate and MCCA were mainly produced without adding nutrients, and high ethanol consumption was observed. A higher metabolic diversification was observed at 37 °C than at 30 °C. Temperature and nutrient availability significantly affected the metabolic pathway and the type of carboxylic acid produced.

Increasing Value of Winery Residues through Integrated Biorefinery Processes: A Review

The wine industry is one of the most relevant socio-economic activities in Europe. However, this industry represents a growing problem with negative effects on the environment since it produces large quantities of residues that need appropriate valorization or management. From the perspective of biorefinery and circular economy, the winery residues show high potential to be used for the formulation of new products. Due to the substantial quantities of phenolic compounds, flavonoids, and anthocyanins with high antioxidant potential in their matrix, these residues can be exploited by extracting bioactive compounds before using the remaining biomass for energy purposes or for producing fertilizers. Currently, there is an emphasis on the use of new and greener technologies in order to recover bioactive molecules from solid and liquid winery residues. Once the bio compounds are recovered, the remaining residues can be used for the production of energy through bioprocesses (biogas, bioethanol, bio-oil), thermal processes (pyrolysis, gasification combustion), or biofertilizers (compost), according to the biorefinery concept. This review mainly focuses on the discussion of the feasibility of the application of the biorefinery concept for winery residues. The transition from the lab-scale to the industrial-scale of the different technologies is still lacking and urgent in this sector.

Hydrogen Production by Immobilized Cells of Clostridium intestinale Strain URNW Using Alginate Beads

Biological hydrogen (H₂) is a promising candidate for production of renewable hydrogen. Using entrapped cells rather than conventional suspended cell cultures for the production of H₂ offers several advantages, such as improved production yields related to higher cell density, and enhanced resistance to substrate and end-product inhibition. In this study, H₂ production by a novel isolate of Clostridium intestinale (strain URNW) was evaluated using cells entrapped within 2% calcium-alginate beads under strictly anaerobic conditions. Both immobilized cells and suspended cultures were studied in sequential batch-mode anaerobic fermentation over 192 h. The production of H₂ in the headspace was examined for four different initial cellobiose concentrations (5, 10, 20, and 40 mM). Although a lag period for initiation of the fermentation process was observed for bacteria entrapped within hydrogel beads, the immobilized cells achieved both higher volumetric production rates (mmol H₂/(L culture h)) and molar yields (mol H₂/mol glucose equivalent) of H₂ compared with suspended cultures. In the current study, the maximum cellobiose consumption rate of 0.40 mM/h, corresponding to 133.3 mg/(L h), was achieved after 72 h of fermentation by immobilized cells, generating a high hydrogen yield of 3.57 mol H₂/mol cellobiose, whereas suspended cultures only yielded 1.77 mol H₂/mol cellobiose. The results suggest that cells remain viable within the hydrogels and proliferated with a slow rate over the course of fermentation. The stable productivity of immobilized cells over 8 days with four changes of medium depicted that the immobilized cells of the isolated strain can successfully yield higher hydrogen and lower soluble metabolites than suspended cells suggesting a feasible process for future applications for bioH₂ production.

Bio-Energy Generation from Synthetic Winery Wastewaters

In Spain, the winery industry exerts a great influence on the national economy. Proportional to the scale of production, a significant volume of waste is generated, estimated at 2 million tons per year. In this work, a laboratory-scale reactor was used to study the feasibility of the energetic valorization of winery effluents into hydrogen by means of dark fermentation and its subsequent conversion into electrical energy using fuel cells. First, winery wastewater was characterized, identifying and determining the concentration of the main organic substrates contained within it. To achieve this, a synthetic winery effluent was prepared according to the composition of the winery wastewater studied. This effluent was fermented anaerobically at 26 °C and pH = 5.0 to produce hydrogen. The acidogenic fermentation generated a gas effluent composed of CO2 and H2, with the percentage of hydrogen being about 55% and the hydrogen yield being about 1.5 L of hydrogen at standard conditions per liter of wastewater fermented. A gas effluent with the same composition was fed into a fuel cell and the electrical current generated was monitored, obtaining a power generation of 1 W·h L−1 of winery wastewater. These results indicate that it is feasible to transform winery wastewater into electricity by means of acidogenic fermentation and the subsequent oxidation of the bio-hydrogen generated in a fuel cell.

Biohydrogen and poly-β-hydroxybutyrate production by winery wastewater photofermentation: Effect of substrate concentration and nitrogen source

The applicability and convenience of biohydrogen and poly-β-hydroxybutyrate production through single-stage photofermentation of winery wastewater is demonstrated in the present study. Experiments are conducted using a purple non-sulfur bacteria mixed consortium, subject to variable nutrient conditions, to analyze the effect of initial chemical oxygen demand and the available nitrogen source on the metabolic response. Results show that winery wastewater is a promising substrate for photofermentation processes, despite the presence of inhibiting compounds such as phenolics. Nonetheless, the initial chemical oxygen demand must be carefully controlled to maximize hydrogen production. Up to 468 mL L^-1 of hydrogen and 203 mg L^-1 of poly-β-hydroxybutyrate can be produced starting from an initial chemical oxygen demand of 1500 mg L^-1. The used nitrogen source may direct substrate transformation through different metabolic pathways. Interestingly, the maximum production of both hydrogen and poly-β-hydroxybutyrate occurred when glutamate was used as the nitrogen source.

Characterization and anaerobic digestion of highly concentrated Mexican wine by-products and effluents

Wine production has increased in recent years, especially in developing countries such as Mexico. This increase is followed by an increase of winery effluents that must be treated to avoid environmental risks. However, little information is available about the characteristics of these effluents and the possible treatments. This paper aimed to characterize the effluents and by-products generated by the Mexican winery industry and to evaluate the performance and stability of the anaerobic treatment using a single-stage and a two-stage process. Results showed that the winery effluents had a high content of biodegradable organic matter, with chemical oxygen demand (COD) values ranging from 221 to 436 g COD/L. The single-stage anaerobic process was able to treat an organic loading rate of 9.6 kg COD/(m³ d); however, it was unstable and highly dependent on the addition of bicarbonate alkalinity (0.31 g NaHCO₃/g COD removed). The two-stage process was more stable working at a higher organic load (12.1 kg COD/(m³ d)) and was less dependent on the addition of bicarbonate (0.17 g NaHCO₃/g COD removed). The results highlight the potential of the winery effluents to produce methane through anaerobic digestion in a two-stage process, making wine production more sustainable.