Increasing levels of freshwater contaminants, mainly due to anthropogenic activities, have resulted in a great deal of interest in finding new eco-friendly, cost-effective and efficient methods for remediating polluted waters. The aim of this work was to assess the feasibility of using a green microalga Desmodesmus sp., a cyanobacterium Nostoc sp. and a hemicryptophyte Ampelodesmos mauritanicus to bioremediate a water polluted with an excess of nutrients (nitrogen and phosphorus) and heavy metals (copper and nickel). We immediately determined that Nostoc sp. was sensitive to metal toxicity, and thus Desmodesmus sp. was chosen for sequential tests with A. mauritanicus. First, A. mauritanicus plants were grown in the ‘polluted’ culture medium for seven days and were, then, substituted by Desmodesmus sp. for a further seven days (14 days in total). Heavy metals were shown to negatively affect both the growth rates and nutrient removal capacity. The sequential approach resulted in high metal removal rates in the single metal solutions up to 74% for Cu and 85% for Ni, while, in the bi-metal solutions, the removal rates were lower and showed a bias for Cu uptake. Single species controls showed better outcomes; however, further studies are necessary to investigate the behavior of new species.

Aquaponics represents an alternative to traditional soil cultivation. To solve the problem of nutrient depletion that occurs in this biotechnological system, the application of a spirulina-based biofertilizer was assessed. The microalgal waste used in this study came from industrial processing. Four different dilutions of the supernatant portion of this waste were sprayed on lettuce plants cultivated in an aquaponics system installed at the Botanical Gardens of the Tor Vergata University of Rome. The biofertilizer was characterized to evaluate its amount of macro- and micronutrients. The analysis conducted on the plants involved both morpho-biometric aspects and qualitative–quantitative measurements. The experiments showed that the spirulina extract had a positive effect on the growth and nutraceutical content of the lettuce plants; the obtained results highlighted that a dilution of 75% was the best for treatment. The use of the proposed organic and recycled fertilizer could increase the sustainability of crop cultivation and promote the functioning of aquaponics systems.

Aquaponics is an innovative agricultural method combining aquaculture and hydroponics. However, this balance can lead to the gradual depletion of essential micronutrients, particularly iron. Over time, decreasing iron levels can negatively impact plant health and productivity, making the monitoring and management of iron in aquaponic systems vital. This study investigates the use of Fe-Alg-CaCO₃ microparticles (MPs) as foliar fertilizer on lettuce plants in an aquaponic system. The research investigated Lactuca sativa L. cv. Foglia di Quercia Verde plants as the experimental cultivar. Three iron concentrations (10, 50, and 250 ppm) were tested, with 15 plants per treatment group, plus a control group receiving only sterile double-distilled water. The Fe-Alg-CaCO₃ MPs and ultrapure water were applied directly to the leaves using a specialized nebulizer. Foliar nebulization was chosen for its precision and minimal resource use, aligning with the sustainability goals of aquaponic cultivation. The research evaluated rosette diameter, root length, fresh weight, soluble solids concentration, levels of photosynthetic pigments, and phenolic and flavonoid content. The 250 ppm treatment produced the most notable enhancements in both biomass yield and quality, highlighting the potential of precision fertilizers to boost sustainability and efficiency in aquaponic systems. In fact, the most significant increases involved biomass production, particularly in the edible portions, along with photosynthetic pigment levels. Additionally, the analysis of secondary metabolite content, such as phenols and flavonoids, revealed no reduction compared to the control group, meaning that the proposed fertilizer did not negatively impact the biosynthetic pathways of these bioactive compounds. This study opens new possibilities in aquaponics cultivation, highlighting the potential of precision fertilizers to enhance sustainability and productivity in soilless agriculture.

The possibility of modifying the surface chemistry of materials and synthetizing inorganic particles in natural aqueous extracts of plants (avoiding calcination), opens the doors to undoubtedly interesting scenarios for innovative functionalization strategies that are increasingly eco-sustainable and rich in interesting chemical–physical and biochemical properties. Among the aerial plants, Satureja montana exhibits interesting antibacterial, antifungal, antimicrobial, and antioxidant activities due to the rich volatile and non-volatile compounds (characterized by gas chromatography–mass spectrometry), contained in the aqueous extracts. For the first time, the latter was applied for the green synthesis of TiO₂ and CaCO₃ particles, characterized by X-ray diffraction, Raman, infrared spectroscopies, and scanning electron microscopy, coupled with microanalysis. Screening through antimicrobial assays under indoor passive sedimentation conditions showed opposite trends for two kinds of particles. TiO₂ anatase spherical particles (400 < φ < 600 nm) increase microbial growth, proportionally to increasing particle concentration. Instead, S. montana-functionalized CaCO₃ prismatic microparticles (1 µm × 1 µm × 1 µm) exhibit strong and dose-dependent antimicrobial activities, achieving near-complete inhibition at 50 mg/mL.

The possibility of modifying the surface chemistry of materials, synthetizing inorganic particles in natural aqueous extracts of plants (at low temperature, avoiding calcination), opens the doors to undoubtedly very interesting scenarios for innovative functionalization strategies that are increasingly eco-sustainable and rich in interesting chemical-physical and biochemical properties. Among the aerial plant, Satureja montana exhibits interesting antibacterial, antifungal, antimicrobial and antioxidant activities due to the rich volatile and non-volatile compounds (as activators/phase controllers characterized by Gas Chromatography-Mass Spectrometry, GC-MS), contained in the aqueous extracts. For the first time, the aqueous extract of Satureja montana plant was applied for the green synthesis of TiO2 and CaCO3 particles, characterized by X-Ray diffraction (XRD), Raman, Infrared/IR spectroscopies, and Scanning Electron Microscopy-SEM/coupled by microanalysis EDX. Screening through antimicrobial assays under indoor passive sedimentation conditions showed opposite trends for both kind of inorganic particles. TiO₂ Anatase spherical particles (400<<600 nm) increase microbial growth, proportionally to increasing particles concentration (dose-dependent response). Probably, the low surface area (1.20 m2/g), low porosity (pore volume 0.0023 cm3/g; pore size of 560 nm) and smooth spherical morphology, don’t provoke chemical or physical damages to microorganisms, and therefore microbial growth is not inhibited. This occurs in the presence of medium/low concentrations of ROS (oxygenated radical species), which are chemically active in generating oxidative stress and cell death. In fact, the chemically reactive defects found in these TiO2/Anatase particles are predominantly carbonyl in nature, less reactive than carboxylic ones in producing ROS. Instead, S. montana-functionalized CaCO₃ prismatic microparticles (1µm x 1µm x 1µm) exhibit strong and dose-dependent antimicrobial activities, achieving near-complete inhibition at 50 mg mL⁻¹. This could be related to the molecular activators/phase controllers that induced defects, edges, dislocations and chemical active surface functionalities on the prismatic calcite particles, making them capable of inhibiting microbial activity. In particular, the presence of carboxyl groups C=(O)-OH, recorded by FTIR on the prismatic surfaces of CaCO3 MPs/SM particles, could be responsible for the production of ROS, the latter known to be dangerous sentinels of oxidative stress and cell death.