Trypsin Inhibitor from Soybean Whey Wastewater: Isolation, Purification and Stability

Abstract

Soybean trypsin inhibitor (STI) was obtained from simulated soybean whey wastewater through a sustainable method consisting of isoelectric precipitation, ammonium sulfate salting out, and gel filtration chromatography, and the effect of temperature, pH, and pepsin on the stability of STI was also discussed. The results showed that the recovery rate of the trypsin inhibitory activity was 89.47%, the purity and the specific activity of STI were 71.11%, and 1442.5 TIU/mg in the conditions of pH 4.0 and 40% ammonium sulfate saturation. The soybean Kunitz trypsin inhibitor (KTI) and soybean Bowman–Brik trypsin inhibitor (BBI) were obtained via gel filtration chromatography, and their specific activity levels were 1733.5 TIU/mg and 2588.3 TIU/mg, respectively. The STI displayed good stability over a wide temperature and pH range. The STI, KTI, and BBI were all resistant to pepsin hydrolysis, and their ability was ranked as BBI > STI > KTI. These findings will provide a theoretical basis for recycling STI from soybean whey wastewater and promoting better active compound utilization.