Co-utilizing tofu whey with food waste digestate enhances techno-economic feasibility of microalgal single-cell protein production

Food waste digestate is a promising substrate for microalgal single-cell protein (SCP) production, but its dark color, high turbidity, elevated ammoniacal nitrogen, and salt content impede microalgae growth. Dilution with freshwater alleviates these issues but concurrently lowers essential nutrient concentrations, limiting biomass yield. This study evaluated tofu whey as an alternative diluent. Using 0.2 μm-filtered digestate at 10 % dilution, Chlorella sorokiniana achieved 0.4 g/L biomass, which increased to 2.0 g/L with synthetic nutrient supplementation. Completely replacing freshwater and synthetic nutrients with tofu whey further enhanced biomass concentration to 2.7 g/L, while lowering cultivation costs by 66 % relative to the conventional Bold’s Basal Medium. The resulting biomass contained up to 62 % protein (dry weight) and was free from toxic heavy metals, supporting its suitability as SCP. These findings demonstrate that tofu whey improves digestate utilization for microalgal SCP production, promotes cost savings, and advances sustainable nutrient recycling in the circular bioeconomy.