HYDROLYSIS OF GALACTOOLIGOSACCHARIDES BY COMMERCIAL PREPARATIONS OF ALPHA-GALACTOSIDASE AND BETA-FRUCTOFURANOSIDASE - POTENTIAL FOR USE AS DIETARY ADDITIVES

In vitro and in vivo studies were conducted with six commercial enzyme preparations (SP249, Energex, Rohament CW, Novozyme 230 and crude alp ha-galactosidase) to determine their effectiveness in hydrolysing gala ctooligosaccharides from soya bean and canola meal in the gastrointest inal tract of poultry. The use of the enzyme invertase to enhance gala ctoside hydrolysis was also studied. A wide range of alpha-galactosida se activity was observed in vitro, with crude alpha-galactosidase from Mortierella vinacea and Novozyme 230 preparation showing the highest activity values of 4.3 and 1.5 nkat mg(-1) respectively. All preparati ons with the exception of crude alpha-galactosidase showed invertase a ctivity which is known to convert raffinose and stachyose to the corre sponding di- and trisaccharide, melibiose and manninotriose. Although the activity of invertase was highest on sucrose, the Novozyme 230 pre paration showed activity values of 4.2 and 2.3 nkat mg(-1) toward raff inose and stachyose substrates, respectively. De novo synthesis of raf finose was observed when soya bean meal, canola meal or pure sucrose a nd galactose were incubated with certain enzyme preparations (ie Energ ex). In general, preparations possessing hydrolytic activity towards g alactooligosaccharides showed very little synthesis of raffinose while preparations capable of generating raffinose were very weak in the hy drolysis of galactooligosaccharides. The best result in terms of galac tooligosaccharide in vitro hydrolysis of canola and soya bean meal was obtained with a combination of alpha-galactosidase and invertase. In the in vivo study with caecectomised hens, hydrolysis of galactooligos accharides averaged 88% when crude alpha-galactosidase (2 g kg(-)1) an d invertase (1 g kg(-1)) were added to laying hen diet containing 200 g soya bean meal per kilogram. A problem identified in the current stu dy was that minerals such as calcium phosphate and calcium carbonate c ommon in poultry diets inhibit the hydrolysis activity of alpha-galact osidase, indicating that high levels of activity would be required to yield a response in practical poultry feeding.