Fermentation is an ancient method used worldwide to process and preserve food while enhancing its nutraceutical profile. Alga-based fermented products have recently been developed and tested due to growing interest in healthy sustainable diets, which demands the development of innovative practices in food production, operating for both human health and Earth sustainability. Algae, particularly microalgae such as Arthrospira platensis, Chlorella vulgaris, and Dunaliella salina, are already cultivated as sources of food due to their valuable compounds, including proteins, pigments, lipids, carotenoids, polyunsaturated fatty acids, steroids, and vitamins. Due to their nutritional composition, functional diversity, and flexible metabolism, microalgae represent good fermentation substrates for lactic acid bacteria (LAB) and yeasts. This review presents an overview of the scientific studies on microalga fermentation underlining microalgae’s properties and health benefits coupled with the advantages of LAB and yeast fermentation. The potential applications of and future perspectives on such functional foods are discussed.

Digestate is a complex by-product of anaerobic digestion and its composition depends on the digestor inputs. It can be exploited as a sustainable source of nutrients for microalgae cultivation but its unbalanced composition and toxic elements make the use challenging. Screening algae in a simplified synthetic digestate which mimics the main nutrient constraints of a real digestate is proposed as a reproducible and effective method to select suitable species for real digestate valorisation and remediation. Growth performance, nutrient removal and biomass composition of eight microalgae exposed to high amounts of NH₄⁺, PO₄^- and organic-C were assessed. Using a score matrix, A. protothecoides, T. obliquus, C. reinhardtii, and E. gracilis were identified as the most promising species. Thus, three strategies were applied to improve outcomes: i) establishment of an algal consortium to improve biomass production, ii) K⁺ addition to the medium to promote K⁺ uptake over NH₄⁺ and to reduce potential NH₄⁺ toxicity, iii) P starvation as pretreatment for enhanced P removal by luxury uptake. The consortium was able to implement a short-term response displaying higher biomass production than single species (3.77 and 1.03-1.89 mg mL^-1 respectively) in synthetic digestate while maintaining similar nutrient remediation, furthermore, its growth rate was 1.6 times higher than in the control condition. However, the strategies aiming to reduce NH₄⁺ toxicity and higher P removal were not successful except for single cases. The proposed algal screening and the resulting designed consortium were respectively a reliable method and a powerful tool towards sustainable real digestate remediation.

Due to the increasing production of wastewater from human activities, the use of algal consortia for phytoremediation has become well‐established over the past decade. Understanding how interspecific interactions and cultivation modes (monocultures vs. polyculture) influence algal growth and behaviour is a cutting‐edge topic in both fundamental and applied science. Ammonium‐rich growth media were used to challenge the monocultures of Auxenochlorella protothecoides, Chlamydomonas reinhardtii and Tetradesmus obliquus, as well as their polyculture; NO₃⁻ was also used as the sole nitrogen chemical form in control cultures. The study primarily compared the growth, carbon and nitrogen metabolisms, and protein content of the green microalgae monocultures to those of their consortium. Overall, the cultivation mode significantly affected all the measured parameters. Notably, at 50 mM NH₄⁺, the assimilation rates of carbon and nitrogen were at least twice as high as those in the monoculture counterparts, and the protein content was three times more abundant.Additionally, the consortium's response to NH₄⁺ toxicity was investigated by observing a linear relationship between the indicator of tolerance to NH₄⁺ nutrition and the N isotopic signature. The study highlighted a high degree of acclimation through metabolic flexibility and diversity, as well as species abundance plasticity in the consortium, resulting in a functional resilience that would otherwise have been unattainable by the respective monocultures.

Biostimulants are a sustainable tool for enhancing crop productivity while reducing dependency on fertilizers. This study aims to investigate the biostimulant effect of algal cell extracts and spent growth media (supernatants post biomass separation) on tomato (Solanum lycopersicum L.) seeds. Both extracts and media were obtained from three chlorophytes (Tetradesmus obliquus, Chlamydomonas reinhardtii and Auxenochlorella protothecoides) and their microalgal consortium which were grown in replete standard medium. Additionally, the consortium was cultured in diluted digestate. Three concentrations of algal extract (0.05, 0.1, and 0.2 mg mL⁻¹) and spent medium (10%, 50%, and 100%) were applied by seed priming. Results revealed concentration-dependent biostimulant effects, with the algal species contributing moderately to the observed variability. Seeds treated with 0.1 mg mL⁻¹ algal extract or 50% spent medium achieved up to 100% germination compared to 86% when treated with water. Additionally, they exhibited significantly greater root and shoot growth, up to 40% longer than controls, despite a delay in germination. When treatments utilized T. obliquus extract or spent medium, the overall yields were the highest. Conversely, treatments utilizing extract or spent medium from the digestate grown-consortium resulted in the lowest yields, even below control levels. This highlights the critical role growth medium plays in determining the composition of algal biomass, which in turn affects the efficacy of biostimulants. The study underscores the potential of algal-derived biostimulants in enhancing seed germination and seedling development. It also emphasizes the critical role of selecting and optimizing growth media to fully harness the benefits of algae as biostimulants.

Adsorption is a method widely used to remove low-molecular-weight organics from wastewaters, and phenolic compounds from olive mill wastewater are a persistent class of bioactive pollutants of environmental concern. We screened eleven microalgal candidates at 0.10 g·L⁻¹ using batch kinetics fitted with the Lagergren pseudo-first-order model to obtain rate constants (k) and fitted equilibrium capacities (q_e). Cyanobacteria, particularly Anabaena spp. and Limnospira platensis, exhibited the highest adsorptive potential in the screening; wall-less species (e.g., Dunaliella salina, Isochrysis galbana) showed negligible surface adsorption, indicating that the presence and type of cell wall highly influence biosorption. L. platensis was selected for detailed study because of its established industrial cultivation and valorisation potential. Equilibrium experiments with HCl-functionalized L. platensis at four biomass loadings (0.10–1.00 g·L⁻¹; initial phenolic mix 30 mg·L⁻¹) showed that increasing dose reduced equilibrium concentration (C_e) but decreased specific uptake from ≈77 mg·g⁻¹ to ≈18 mg·g⁻¹ while removal rose from ~26% to ~61%. Nonlinear isotherm fitting favoured the Freundlich model (1/n < 1), consistent with heterogeneous, multi-site adsorption. Targeted macromolecular extractions abolished phenol uptake, demonstrating that the intact protein–polysaccharide matrix is essential for binding. L. platensis route delivered higher single-cycle removal (≈61%) compared to the maize-derived activated carbon reference (≈49%) while also incurring a 1.3-fold lower GWP (approximately 3 kg CO₂-eq per treatment) than the activated carbon route (approximately 4 kg CO₂-eq per treatment) in our model. Overall, L. platensis represents a lower-impact alternative for natural phenols remediation, especially when integrated into valorisation pathways that recover algal co-products.

This report presents the activities and outcomes of an educational project aimed at promoting sustainable food awareness among high-school students in Italy through the active contributions from young researchers, profit partners and school educators. The project involved two final-year classes—one from a scientific lyceum and one from a technical chemistry institute—and integrated theoretical lessons, laboratory activities, and experiential learning focused on planetary boundaries, sustainable diets, and alternative proteins such as from algae and insects. To assess the impact of the project, pre- and post-intervention questionnaires were administered and are here discussed. The intervention significantly enhanced the students’ cognitive and affective engagement both during the sessions and in the immediate aftermath, as evidenced by elevated levels of satisfaction and retention of key concepts. Overall, the project fostered great environmental awareness and openness to sustainable food choices, demonstrating the potential of targeted hands-on educational programs to influence both attitudes and behaviours in younger generations of western high-income countries. The project serves as a replicable model of a transdisciplinary approach for integrating Education for Sustainable Development (ESD) and education for Planetary Health into secondary school curricula.