Treatment of sugarcane bagasse for the immobilization of soybean β-glucosidase and application in soymilk isoflavones

Abstract Sugarcane bagasse from agro-industrial residues was autoclaved at 121 °C for 15 min, treated with 2% NaOH and activated with 2.5% glutaraldehyde for the immobilization of soybean β-glucosidase. Scanning electron microscopy, energy dispersive X-ray spectroscopy and Fourier transform infrared spectroscopy characterized and confirmed the immobilization of the β-glucosidase on the sugarcane bagasse. The immobilization efficiency was influenced by the type of bagasse modification and was 99% at maximum. The optimum immobilization conditions were 1 mg mL-1 protein, pH 7.0, 2.5% glutaraldehyde, 110 rpm and 8 h of incubation at 4 °C. The immobilized system could be reused for 15 cycles without the complete loss of activity. The thermal stability indicated a residual activity of 15% after 180 min incubation at 70 °C. The conversion efficiency of glucosides to aglycones in commercial soymilk by β-glucosidase immobilized on sugarcane bagasse was evaluated and the total aglycone content increased by 23.8% after incubation at 50 °C for 120 min.