Utilization of tofu processing wastewater as a source of the bioactive peptide lunasin

•A sustainable approach for the valorization of tofu whey was provided.•Lunasin was present in tofu by-products okara and whey.•A 3-step method was developed to isolate lunasin from tofu whey with 80% purity.•The 80% pure lunasin was active against lipopolysaccharide activated macrophages. The goal of our study was to design a simple and feasible method to obtain lunasin, a naturally-occurring bioactive peptide, from tofu whey wastewater. A combination of alcoholic precipitation of high-molecular weight proteins from the whey, isoelectric precipitation of lunasin enriched material, and purification via gel filtration chromatography was selected as the best approach using tofu whey prepared at the laboratory scale. This process was applied to tofu whey produced by a local tofu factory and 773 mg of 80% purity lunasin was obtained per kg of dry tofu whey. Significant reduction of nitric oxide, and pro-inflammatory cytokines TNF-α and IL-6 over lipopolysaccharide activated murine macrophages demonstrate its biological activity. Our three-step process is not only simpler and faster than the previously reported methods to obtain lunasin but provides a sustainable approach for the valorization of a waste product, promoting the better utilization of soybean nutrients and active compounds.