ABSTRACT
Usually glycosidases such as β-galactosidase hydrolyze glycosidic linkages but when reaction conditions are manipulated in vitro molecules other than water can be accepted as nucleophiles and new glycosides are obtained (Toone et al. 1989). This method is called transglycosylation. In recent years, considerable attention has focused on the transglycosylation activity of β-galactosidase based on the enormous potential for synthesis of novel oligosaccharides in food, pharmaceutical and medical applications. Non-digestible galacto-oligosaccharides (NDOs) are carbohydrates, which are resistant to gastro-intestinal digestive enzymes, but are fermented by specifi c colonic bacteria. These carbohydrates benefi cially affect the host by selectively stimulating the growth and/or activity of one or a limited number of bacteria in the colon and are recognized as prebiotics (Gibson and Roberfroid 1995, Fuller and Gibson 1997). The microbial community in the large intestine is extremely complex, both in terms of the number of organisms and its diversity. This complex and highly adapted community benefi ts the host by providing resistance to pathogens. It is diffi cult for other organisms, including pathogens, to colonise in the lumen of the small intestine. This generates colonization resistance or non-specifi c disease resistance in the gut which acts as an important line of defence against pathogens (Tannock 1995). In addition to their prebiotic activity, some NDOs, including galacto-oligosaccharides, have also been investigated for other health promoting properties. They have been shown to consistently increase absorption and retention of several minerals, particularly calcium, magnesium and iron and to improve mineralization of bone (Miniello et al. 2004). Galacto-oligosaccharides are also used in pastry, jam and bread-making because of their heat stability, allowing the sweetness of the products to be controlled (Bhat 1998). Oligomate 50 is a heat stable (stable at temperatures of 100°C), non cariogenic galacto-oligosaccharide that is added to food products e.g., ice cream, to prevent lactose crystallization. This galacto-oligosaccharide has water binding properties which is important in maintaining a healthy gut, by assisting in the control of constipation and decreasing blood NH3 content.
