Sofía Martínez-López

Background The agricultural sector is one of the leading producers of agro-industrial solid organic waste. This waste, mainly disposed of by incineration or landfilled, could be used for the production of high-value chemicals. In this study, a fermentation process for the production of microbial oil from waste lemon extract (LE), an aqueous side-stream deriving from waste lemon peel and pulp processing, was developed and assessed for its impact. Microbial oil can have many diverse applications, from plasticizers in plastic and rubber compounds to moisturizers in cosmetic formulations. Methods and results Characterization of LE revealed that its autoclaving process is effective for increasing the concentration of readily available glucose and fructose, reaching 28.77 ± 0.08 g L -1 and 25.68 ± 0.27 g L -1. Nitrogen content was measured too, revealing a C/N ratio of 85, optimal for triggering lipid accumulation in the selected microbial cell factory. Therefore, the oleaginous yeast Cutaneotrichosporon oleaginosum was cultivated in an unmodified LE-based medium in 2 L bioreactors, resulting in a lipid accumulation of 0.47 ± 0.08 g oil g CDW -1. Finally, a new lipid extraction method using green solvents was developed, which allowed to extract and purify 11.79 g of oil, corresponding to 35% of the cell dry weight. The carbon footprint of this laboratory-scale production was estimated to be 71 – 434 kgCO 2eq kg -1 of microbial oil, with electricity consumption of the fermentation step as the main factor. Sensitivity analysis suggests that the overall impact can be reduced with process optimization and scale-up. Conclusions The proposed process is promising in terms of production and does not compete with edible resources and land use. However, the microbial oil yield and the downstream must be optimized to make the process sustainable.

Background The agricultural sector is one of the leading producers of agro-industrial solid organic waste. This waste, mainly disposed of by incineration or landfilled, could be used for the production of high-value chemicals. In this study, a fermentation process for the production of microbial oil from waste lemon extract (LE), an aqueous side-stream deriving from waste lemon peel and pulp processing, was developed and assessed for its impact. Microbial oil can have many diverse applications, from plasticizers in plastic and rubber compounds to moisturizers in cosmetic formulations. Methods and results Characterization of LE revealed that its autoclaving process is effective for increasing the concentration of readily available glucose and fructose, reaching 28.77 ± 0.08 g L -1 and 25.68 ± 0.27 g L -1. Nitrogen content was measured too, revealing a C/N ratio of 85, optimal for triggering lipid accumulation in the selected microbial cell factory. Therefore, the oleaginous yeast Cutaneotrichosporon oleaginosum was cultivated in an unmodified LE-based medium in 2 L bioreactors, resulting in a lipid accumulation of 0.47 ± 0.08 g oil g CDW -1. Finally, a new lipid extraction method using green solvents was developed, which allowed to extract and purify 11.29 g of oil, corresponding to 35% of the cell dry weight. The carbon footprint of this laboratory-scale production was estimated to be 71 – 434 kgCO 2eq kg -1 of microbial oil, with electricity consumption of the fermentation step as the main factor. Simulation of the process in a 300 L fermenter suggests that the overall impact can be drastically reduced with scale-up. Conclusions The proposed process is promising in terms of production and does not compete with edible resources and land use. However, the microbial oil yield and the downstream must be optimized to make the process sustainable.

The reuse of reclaimed water is essential for sustainable water management in arid regions. However, despite advancements in Wastewater Treatment Plants (WWTPs), certain micropollutants may persist. To address these challenges, the recently enacted European Urban Wastewater Treatment Directive (UWWTD) has established strict standards focused on monitoring twelve specific indicator compounds. In line with this, the present study aims to evaluate the concentrations and potential risks of these twelve UWWTD-designated compounds across various water sources, including surface water, groundwater, and effluents from a WWTP in the southeast of Spain. Although none of the evaluated water sources are, as expected, intended for human consumption, risks were assessed based on worst-case scenarios that could amplify their impact. The study assessed potential risks to human health across different age groups and ecosystems, focusing on key organisms such as fish, daphnia, and algae, using empirical assessment approaches. The risk assessment identified a low risk for most compounds regarding human health, except for citalopram (HRQ = 19.116) and irbesartan (HRQ = 1.104), which showed high human risk quotients (HQR > 1) in babies, particularly in reclaimed water. In terms of ecotoxicological risk, irbesartan presented the highest ecological risk quotient (ERQ = 3.500) in fish, followed by clarithromycin, with algae (ERQ = 1.500) being the most vulnerable organism. Furthermore, compounds like citalopram, venlafaxine, and benzotriazole exhibited moderate ecological risks (ERQ between 0.1 and 1) in the reclaimed water, and their risk was reduced in surface water and groundwater. Finally, this study discussed the potential impacts of elevated concentrations of these emerging compounds, emphasizing the need for rigorous wastewater monitoring to protect human health and ecosystem integrity. It also revealed notable differences in risk assessment outcomes when comparing two distinct evaluation approaches, further highlighting the complexities of accurately assessing these risks.

The revalorization of artichoke (Cynara scolymus L.) by-products is a promising strategy to obtain bioactive compounds with antioxidant properties, supporting a circular economy approach. This study compares the efficiency of an enzymatic pretreatment followed by microwave-assisted extraction (EMAE), ultrasound-assisted extraction (EUAE), and ultrasound-microwave-assisted extraction (EUMAE) at a pilot scale for recovering antioxidant compounds. Extracts were purified using Diaion^® HP20 resin to obtain phenolic-rich fractions with enhanced antioxidant activity. The results showed that EUAE was the most effective technique, achieving a total phenolic content (TPC) of 210.76 ± 1.40 µmol GAE/g d.w. with an extraction yield of 21.38%. HPLC-MS analysis identified 14 major phenolic compounds, including chlorogenic acid isomers (60.73 mg/g d.e.), caffeic acid (34.29 mg/g d.e.), and luteolin rutinoside (103.27 mg/g d.e.), among others, which contribute to the extracts’ high bioactivity. The antioxidant potential of the extracts was assessed using Folin–Ciocalteu (F-C), ABTS, DPPH, and FRAP assays. EUAE extracts exhibited the highest antioxidant activity values, with F-C: 985.33 ± 4.46 µmol GAE/g d.e., ABTS: 80.46 ± 2.39 µmol TE/g d.e., DPPH: 87.03 ± 1.11 µmol TE/g d.e., and FRAP: 184.99 ± 2.52 µmol TE/g d.e. The purification process using Diaion^® HP20 resin further enhanced TPC and antioxidant activity, with the enzyme–ultrasound-assisted extraction—purified extract (EUAE-PE) reaching a phenolic purity of 50.71% and an F-C value of 2981.35 ± 12.16 µmol GAE/g d.e.

This study explores the potential of storage lagoons as a quaternary treatment step in wastewater treatment plants (WWTPs), focusing on compliance with the recent European Urban Wastewater Treatment Directive (UWWTD), which mandates an 80% reduction in specific micropollutants. While conventional treatments effectively remove residual nutrients and solids, the potential of storage lagoons as an additional treatment is not fully defined. This research aims to address this gap by assessing the efficacy of storage lagoons in refining the effluent quality at the Cabezo Beaza WWTP, considering recent UWWTD requirements. We conduct a comprehensive assessment of the water quality parameters and micropollutants, before and after the storage lagoon stage, at the Cabezo Beaza WWTP. The results indicate that this strategy of prolonged storage in lagoons manages to meet the reduction objectives established by the Directive, reaching elimination percentages greater than 80% for the majority of the analyzed micropollutants. Our findings suggest that lagoons significantly improve water quality and reduce contaminants beyond conventional treatments, offering environmental and economic benefits. This paper discusses the mechanisms behind these improvements, such as natural sedimentation, microbial activity, and potential phytoremediation. This study contributes to the research on advanced wastewater treatment and supports the integration of storage lagoons as a viable quaternary treatment solution that meets the UWWTD standards.