Microalgae-based bioremediation of food and beverage processing wastewater: A sustainable approach toward a circular economy concept

Abstract

Food and beverage production generates large volumes of nutrient-rich wastewaters that pose severe environmental challenges when discharged untreated. Effluents such as nejayote (from tortilla production), tequila vinasses (from tequila distillation), and cheese whey (from cheese production) contain high organic loads and extreme pH values that contribute to eutrophication and ecosystem disruption. Developing sustainable technologies that mitigate pollution while enabling resource recovery is therefore essential for advancing circular and cleaner production. This thesis evaluates microalgae-based bioremediation as an alternative for the treatment and valorization of these agro-industrial effluents. The work encompasses algae adaptation, process scale-up, biomass characterization, and environmental assessment. A UV-mutagenesis and gradual acclimatization strategy enabled Chlorella vulgaris, Haematococcus pluvialis, and Anabaena variabilis to grow in undiluted wastewater, achieving pollutant reductions of 87–99.9% in nejayote, 31–81% in vinasses, and 35–56% in whey. Although substantial, these results indicate that microalgae are best suited as components of a hybrid treatment systems rather than standalone technology. The technology’s scalability was validated through the cultivation of H. pluvialis in 100-L raceway pond, which maintained high remediation performance and biomass productivity despite minor declines associated with evaporation. The biomass showed significant protein and ash content, supporting potential use as biofertilizer, feed ingredient, or nutraceutical ingredient. Biochemical and functional characterization of biomass grown in nejayote and tequila vinasses revealed reduced pigment and phenolic content due to cultivation stress. However, extracts retained cytokine-modulating activity in RAW 264.7 macrophages, indicating potential for use as nutraceutical ingredient, animal feed, or biofertilizers following safety validation. Life Cycle Assessment comparing a microalgae-based vinasse treatment with the conventional industrial process showed similar overall environmental burdens but substantial reductions in terrestrial ecotoxicity and human carcinogenic toxicity. It also highlighted the need for optimization in coagulant sourcing and energy integration. Overall, this work demonstrates that microalgae-based treatment of agro-industrial effluents is technically viable, environmentally promising, and aligned with a circular bioeconomy, while identifying key challenges that must be addressed to enable industrial implementation.