Purification and Characteristics of β-Amylase from Soybean Whey Wastewater

The large-scale production of soybean proteins results in the generation of a significant volume of wastewater, containing a substantial amount of valuable β-amylase. The β-amylase enzyme was purified from the soybean whey wastewater using a three-step process, including alcohol precipitation, ion-exchange chromatography, and gel filtration chromatography. The specific activity of the purified β-amylase was 29,700 U/mg, with an enzyme activity recovery of 17.3% and purification fold of 16.5. The β-amylase had a molecular mass of around 56 kDa and an isoelectric point (pI) value of 4.8. The β-amylase exhibited optimal activity at 55 °C and reasonable stability between 30 °C and 40 °C. The enzyme demonstrated an optimum pH of 6.0 and relative stability in the pH range of 5.0–8.0. Furthermore, the β-amylase activity was stimulated by PMSF, Tween-20, Tween-40, Tween-60, Tween-80, and Triton X-100. In terms of substrate preference, the enzyme hydrolyzed potato starch worked most effectively, followed by amylose, amylopectin, soluble starch, maltose, and pullulan. The purified β-amylase showed Km and Vmax values of 3.62 μM and 1.04 μM/ (g protein min), respectively. The purification process was simple and yielded high purification and recovery. The β-amylase from soybean whey wastewater has potential applications in the food and beverage industries.