Valorising Whey: from Environmental Burden to Bio-Based Production of Value-Added Compounds and Food Ingredients

Cheese manufacturing generates large volumes of whey with high biochemical and chemical oxygen demand, historically treated as waste. Yet, whey is rich in lactose, proteins, and minerals that can be fractionated and upgraded into foods and bio-based products. During cheese production, 80% to 90% of the total volume is discarded as whey, which can cause severe pollution. However, milk by-products can be a natural source of high-value-added compounds and a cost-effective substrate for microbial growth and metabolites production. The current review focuses on cheese whey as a key milk by-product, highlighting its generation and composition, the challenges associated with its production, methods for fractionating whey to recover bioactive compounds, its applications in functional food development, the barriers to its broader use in the food sector, and its potential as a substrate for producing value-added compounds. Particularly, the focus was on the recent solutions to use cheese whey as a primary material for microbial fermentation and enzymatic processes, producing a diverse range of chemicals and products for applications in the pharmaceutical, food, and biotechnology industries. This review contributes to defining a framework for reducing the environmental impacts of whey through its application in designing foods and generating biomaterials.