Hydrolysis of Oligosaccharides by a Thermostable α-Galactosidase from Termitomyces eurrhizus

The genus of Termitomyces purchased from the market has been identified as Termitomyces eurrhizus using the Internal Transcribed Spacer (ITS) method. An α-galactosidase from T. eurrhizus (TEG), a monomeric protein with a molecular mass of 72 kDa, was purified 146 fold by employing ion exchange chromatography and gel filtration. The optimum pH and temperature was 5.0 and 60 °C, respectively. TEG was stable over pH 2–6, and also exhibited good thermostablility, retaining 100% of the original activity after incubation at 60 °C for 2 h. Inhibition of the enzyme activity by N-bromosuccinimide (NBS) constituted evidence for an essential role of tryptophan in the catalytic action of the isolated enzyme. Besides 4-nitro-phenyl α-d-galactophyranoside (pNPGal), natural substrates could also be effectively hydrolyzed by TEG. Results of thin-layer chromatography (TLC) revealed complete enzymatic hydrolysis of raffinose and stachyose to galactose at 50 °C within 6 h. These properties of TEG advocate its utilization for elevating the nutritional value of soymilk.