Biochemical characterization and insights into the potency of the acidic Aspergillus niger NRC114 purified α-galactosidase in removing raffinose family oligosaccharides from soymilk yogurt.

Background: Because humans lack α-galactosidase, foods containing certain oligosaccharides from the raffinose family, such as soybeans and other legumes, may disrupt digestion and cause flatulence.

Results: Aspergillus niger NRC114 α-galactosidase was purified using protein precipitation, gel filtration, and ion exchange chromatography steps, which resulted in a 123-fold purification. The purified enzyme was found to be 64 kDa using the SDS-PAGE approach. The optimum pH and temperature of the purified α-galactosidase were detected at pH 3.5 and 60 ºC, respectively. The pure enzyme exhibited potent acidic pH stability at pH 3.0 and pH 4.0 for 2 h, and it retained its full activity at 50 ºC and 60 ºC for 120 min and 90 min, respectively. The enzyme was activated using 2.5 mM of K, Mg, Co, or Zn by 14%, 23%, 28%, and 11%, respectively. The K and V values of the purified enzyme were calculated to be 0.401 µM and 14.65 μmol min, respectively. The soymilk yogurt showed an increase in its total phenolic content and total flavonoids after enzyme treatment, as well as several volatile compounds that were detected and identified using GC-MS analysis. HPLC analysis clarified the enzymatic action in the hydrolysis of raffinose family oligosaccharides.

Conclusion: The findings of this study indicate the importance of A. niger NRC114 α-galactosidase enzyme for future studies, especially its applications in a variety of biological fields.