Oligosaccharides act as the high efficiency stabilizer for β-galactosidase under heat treatment

Abstract

β-Galactosidase (β-Gal) as dietary supplement has the ability to alleviate symptoms of lactose intolerance. This study investigated the ability of oligosaccharides to protect β-Gal against heat stress. Four kinds of oligosaccharides including Isomalto-oligosaccharides (IMO), Xylo-oligosaccharides (XOS), Konjac-oligosaccharides (KOS), and Mycose significantly increased the activity retention of β-Gal under heat treatment. The results of three assays including circular dichroism, fluorescence, and Fourier transform infrared spectroscopy (FTIR) illustrated that these oligosaccharides could stabilize the secondary and tertiary structure of β-Gal under thermal conditions through hydrogen bond interaction. Unlike these four oligosaccharides, Chito-oligosaccharides (COS) changed the secondary and tertiary structure of β-Gal, thus decreasing its activity retention rate. Under heat treatment, the activity retention rate of β-Gal with optimal composition (30% IMO, w/v and 40% XOS, w/v) reached 82.1%, which was significantly higher than that of the native β-Gal (the activity retention rate of 20%). This study provides an insight into the mechanism by which sugar stabilizes protein under heat stress and offers guidance for application of liquid lactase to food industry.