Economic assessment of single-cell protein production for cheese whey valorization by purple phototrophic bacteria

Agriculture is a major contributor to climate change, accounting for approximately 11% of global greenhouse gas (GHG) emissions and generating substantial amounts of food waste. Cheese whey (CW), a significant by-product of the dairy industry, offers a promising opportunity for resource valorization, contributing to the mitigation of agri-food system impacts and the development of circular value chains capable of replacing unsustainable products. This study assesses the economic feasibility of converting CW into single-cell protein (SCP) through an integrated process combining acidogenic fermentation and cultivation of purple phototrophic bacteria (PPB). Experimental and modelling results show a 75% conversion efficiency during acidogenic fermentation and stable PPB biomass production on fermented CW. This valorization pathway could potentially reduce production costs to as low as €5 per kilogram of biomass, achieving a protein productivity per hectare four times higher than that of soybean meal.