α-Galactosidase Activity of Rumen Bacteria

Abstract

IN a recent search for bacterial α-galactosidases, Carrere, Lambin and Courtois¹ tested many organisms isolated from the intestinal tracts of a wide range of animals including several ruminants. Only one bacterial species, from the guinea pig, containing α-galactosidase was obtained. The authors commented on the apparent rarity of this enzyme in bacteria, although it is fairly widespread in yeasts and plant tissues². Bacteria producing α-galactosidase might be expected in rumen micro-flora, particularly in animals grazing pasture, as small amounts of oligo- and poly-saccharides containing α-linked galactose are present in many pasture plants. In addition the leaves of plants such as red clover (Trifolium pratense) contain up to 1 per cent (dry wt. basis) of lipid bound galactose³, present either as monosaccharide or 6-O-α-D-galactopyranosyl-D-galactose glycosidically joined through a β-link to the lipid glycerol⁴. The ability of rumen bacteria to release this α- and β-linked galactose has not been demonstrated. One rumen organism, Streptococcus bovis, appears to be a potential producer of α-galactosidase, as an extract from cells of one strain of this species has been shown able to hydrolyse melibiose⁵. The action of cell extracts from mixed rumen bacteria and S. bovis on various compounds containing α-linked galactose has, therefore, been investigated.