Enzymic hydrolysis of raffinose and stachyose in soymilk by alpha-galactosidase from Gibberella fujikuroi.

The use of intracellular alpha-galactosidase from Gibberella fujikuroi to remove raffinose and stachyose in soymilk was studied. The optimum conditions for the enzymic hydrolysis of raffinose and stachyose was pH 5.5 to 6.0 at 55 degrees C. Alpha-galactosidase showed optimum activity at pH 5.0 and 50 degrees C with the substrate p-nitrophenyl-alpha-D-galacto-pyranoside (PNGP). The enzyme showed no detectable loss of activity when held more than 8 hr at 50 degrees C. Thin layer chromatography (TLC) revealed the following composition of oligosaccharides in local soybean variety: sucrose, 5.53%; raffinose, 1.95%; and stachyose, 6.1%. Investigation by TLC showed complete hydrolysis of raffinose and stachyose in 3 hr. HPLC analysis of hydrolyzate indicated complete hydrolysis of stachyose, and more than 60% hydrolysis of raffinose in 2.5 hr.