Inside circular economy challenges: “green” application to valorise olive mill wastewater

The food waste valorisation is a challenging opportunity for a green, sustainable, and competitive development of industry. The transition towards more sustainable food systems, as a new “Farm to Fork Strategy”, requires the involvement of all actors of the food system with the final goal to provide healthy, adequate, safe, nutritious, and sustainable food to everyone, taking into account the three pillars of sustainability: environmental, economic and societal. Olive oil production is the main agro-industrial activity in Mediterranean countries, and it is associated with the generation of a large volume of byproducts. The olive mill wastewater (OMWW), represent a by-product rich in bioactive compounds (hydroxytyrosol and tyrosol) and their recycling is a relevant strategy to recover income and to reduce environmental impact. The aim of the present study was to obtain a new functional beverage with a health-promoting effect starting from OMWW. Microfiltered samples of OMWW were subjected to fermentation using different strains, such us Lactiplantibacillus plantarum, Candida boidinii and Wickerhamomyces anomalus in different combinations. During fermentation, phenolic content was monitored and at the end of fermentation organic acids were evaluated. Moreover, the biological activities of microfiltered fermented OMWW samples on HepG2 cell line and Caco-2 cell line were explored. In addition, transepithelial transport through Caco-2 monolayer and cyclooxygenase activity inhibition (oCOX-1 and human COX-2) were evaluated. The results showed that in all OMWW fermented samples an increase in phenol and organic acid contents was detected. In detail, the concentration of hydroxytyrosol reached values of 925.6, 902.5 and 903.5 mg/L in samples fermented with L. plantarum and C. boidinii in single and combined cultures, respectively. Moreover, biological assays showed an increment in active permeability on Caco-2 cell line and an increase of antioxidant and anti-inflammatory activities for all samples. In conclusion, the present study confirmed that the OMWW represents an effective matrix to formulate a new functional beverage with health benefit.