Acid Hydrothermal Amendment of Grape Wine Pomace: Enhancement of Phenol and Carbohydrate Co-Solubilization

Fondecyt Postdoctorado, Agencia Nacional de Investigacion y Desarrollo de Chile, ANID 321062

Impact of monoterpenes in the stability of the anaerobic digestion of Mediterranean Wholesale Market Waste

The stability and robustness of long-term anaerobic digestion process of fruit and vegetable waste (FVW) generated in Mediterranean wholesale markets were assessed, monitoring potential inhibitory volatile organic compounds (VOCs) such as volatile fatty acids (VFAs) and/or monoterpenes. Particle size (4 and 10 mm) and organic loading rate (OLR) were evaluated during the experimentation. Anaerobic digestion remained stable at OLR of 1.0 g VS L−1 d−1 (VS, total volatile solids) regardless of the feedstock particle size. At this OLR, methane yield was 254 ± 8 and 229 ± 11 mL CH4 g VS−1 for 4 and 10 mm, respectively. As the OLR increased above 1.0 g VS L−1 d−1, the system rapidly destabilized, and a high accumulation of VFAs was observed. In parallel of to the VFAs accumulation, other VOCs such as fenchone also reached concentrations that contributes to the destabilisation of the process. The destabilization process at an OLR of 3.0 g VS L−1 d−1 also resulted in a drastic reduction in the relative abundance and species diversity of methanogenic archaea in all digesters.Employing circular economy approach for OFMSW management within the Mediterranean countries – CEOMED” number A_B.4.2_0058, funded under the ENI CBC MED 2014 – 2020 programmeSpanish Ministry of Science and Innovation for funding this research through the project PID2020-116698RB-I00Universidad de Granada / CBU

Enhancing the recovery of volatile fatty acids from strawberry extrudate through anaerobic fermentation at different pH values

The authors are very grateful to the Spanish Ministry of Science and Innovation for funding this research through the project PID2020-116698RB-100. Antonio Serrano is grateful to the Spanish Ministry of Science, Innovation, and Universities for his Juan de la Cierva-Incorporacion fellowship (IJC2019-040933-I) and to the Economic Transformation, Industry, Knowledge and Universities Department of the Andalucia Autonomous Government for his Emergia fellowship (EMERGIA20_00114). The authors are grateful to the Regional Government of Andalusia, Junta de Andalucia, Consejeria de Economia y Conocimiento (Project UHU-1257728), for providing additional financial support. Funding for open access charge: Universidad de Granada/CBUA. The authors also wish to express their gratitude to Javier Ramiro-Garcia and Ainoa Botana Samper for their assistance with this research.Strawberry extrudate (SE) is a by-product derived from the elaboration of strawberrytasted products. Adequate management of this substrate would entail a new source of benefit for the berry sector, instead of a costly waste to be treated. The aim of this work is to assess the potential use of SE as a carbon soured for volatile fatty acids (VFA) production through anaerobic fermentation at controlled pH (5, and 9) and without pH control (operational pH around 7). Anaerobic digestion at pH 7 resulted in a negligible accumulation of VFA, being mainly degraded to methane. The operation at the other pHs resulted in a marked drop in methane production and, thus, the accumulation of VFA. At pH 9, around 50% of the fed CODtot (total chemical oxygen demand) was accumulated as VFA. Acetic acid represented 61% of these total VFA. The operation at pH 5 resulted in a lower VFA accumulation, i.e. 15% fed CODtot, although the VFA profile was more complex than at pH 9. Propionic and butyric acids represented 43% and 32%, respectively, of the total VFA accumulated at pH 5.Spanish Government PID2020-116698RB-100 IJC2019-040933-IEconomic Transformation, Industry, Knowledge and Universities Department of the Andalucia Autonomous Government EMERGIA20_00114Regional Government of Andalusia, Junta de Andalucia, Consejeria de Economia y Conocimiento UHU-1257728 Universidad de Granada/CBU

Effect of harvesting time in the methane production on the anaerobic digestion of microalgae

Microalgae are being proposed as excellent substrates for different biorefinery processes. Anaerobic digestion process of microalgae is one of these interesting processes but has some limitations in deleting cell walls. For this reason, many studies proposed different types of pre-treatments, entailing energy, operation, and investment costs. This work aims to optimize the anaerobic digestion of the microalgae Chlorella sorokiniana and Chlorella sorokiniana (strain S12/S13/S16) without any pre-treatment by selecting the optimal harvesting time. The greatest influence is seen at 5:00 PM in methane production for both microalgae. For Chlorella sorokiniana, it is the most optimal moment for anaerobic digestion, whereas Chlorella sorokiniana (strain S12/S13/S16) is the least optimal. In the other harvesting times, both microalgae present a similar methane production, i.e. 173 ± 12 mL CH4/g of total volatile solids. The highest methane production rate values were obtained during peak sunlight, 1:00 PM and 8:00 AM, respectively, and lower overnight

Effect of metals on mesophilic anaerobic digestion of strawberry extrudate in batch mode

This research was funded by the Spanish Ministry of Economy, In- dustry, and Competitiveness through the Research Project CTM 2017- 83870-R.Supplementary data to this article can be found online at https://doi. org/10.1016/j.jenvman.2022.116783According to recent studies, the anaerobic digestion of strawberry extrudate is a promising option with potential in the berry industry biorefinery. However, the lack and/or unbalance of concentrations of metals in some agroindustrial residues could hamper methane production during the anaerobic digestion of these kinds of wastes. In this study, a fractional factorial design was applied to screen the supplementation requirements regarding six metals (Co, Ni, Fe, Cu, Mn, and Zn) for methane production from strawberry extrudate (SE). The logistic model was used to fit the experimental data of methane production-time. It allowed identifying two different stages in the anaerobic process and obtaining the kinetic parameters for each step. Maximum methane production obtained in the first (Bmax) kinetic stage, the methane production in the second stage (P), and the maximum methane production rates (Rmax) concluded a statistically significant effect for Ni and Zn. The second set of experiments was carried out with Ni and Zn through a central composite design to study the concentration effect in the anaerobic digestion process of the strawberry extrudate. The parameters P and Rmax demonstrated a positive interaction between Ni and Zn. Although, Bmax did not prove a statistically significant effect between Ni and Zn.Spanish Government CTM 2017-83870-

Interrelating EPS, soluble microbial products and metal solubility in a methanogenic consortium stressed by nickel and cobalt

The relationships between extracellular polymeric substances (EPS), soluble microbial product production, metal solubility, and methanogenic activity were investigated. The individual, and joint, toxic effects of nickel and cobalt on methanogenic consortia fed with glucose as model substrate were studied using biomethane potential assays. Cobalt was found to be less toxic to methanogens than nickel at each concentration tested, and the combined effects of Ni and Co on methane production in the bimetal experiment was higher than the sum of the effects of each metal alone. The protein content of EPS, and extracellular soluble protein fractions, decreased with increasing concentrations of total metals. Meanwhile, no significant change in response to metal stress was apparent for carbohydrate content of EPS or extracellular soluble carbohydrate. Decreasing protein content of EPS was accompanied by reduced methanogenic activity and an increase in the soluble metal fraction. The strong associations observed between these variables could be due to the critical role of EPS in protecting microbial cells against nickel and cobalt stress, possibly by capturing metal cations through their functional groups, thus reducing metal availability to the microbial cells in the methanogenic consortia underpinning the anaerobic digestion process.European Commission 861088Economic Transformation, Industry, Knowledge and Universities Department of the Andalucia Autonomous Government EMERGIA20_0011