Comparative studies of acidic and enzymatic hydrolysis for production of soyasapogenols from soybean saponin

Soyasapogenols, aglycones of soyasaponins, can be produced from crude soybean saponin extract by acid or enzymatic hydrolysis. Soyasapogenol B is known to have hepatoprotective, antimutagenic, antivirus, and anti-inflammatory activities. Hydrolysis of soyabean saponin extract for 72 h with 2 M HCl in methanol gave three soyasapogenols, namely: soyasapogenol D, soyasapogenol B1 and soyasapogenol A. However, the microbial hydrolysis of soybean saponin extract by Aspergillus terreus led to isolation of soyasapogenol B as a major product. A systematic evaluation of the effect of key operational parameters on the microbial transformation was performed. Maximum production of soyasapogenol B (about 152.3 mg/50ml) was observed using 1.5% (w/v) soybean saponin and 1.5% (w/v) glucose, 32°C after 72 h at pH 7 using phosphate buffer. Under these optimal conditions, the cells’ bioconversion efficiency increased from 20.5 to 85.3%. The isolation of soyasapogenols was performed using chromatographic methods and their structures identified on the basis of spectroscopic tools.