Endoglucanase V and a phosphatase from Trichoderma viride are able to act on modified exopolysaccharide from Lactococcus lactis subsp. cremoris B40

EPS B40 from Lactococcus lactis subsp. cremoris consists of a repeating unit of-->4)-beta-D-Glcp-(1-->4)-[alpha-L-Rhap-(1 -->2)][alpha-D-Galp-1-PO4-3]-beta-D-Galp-(1-->4)-beta-D-Glcp-(1-->. A phosphatase from Trichoderma viride was able to release phosphate, but only after removal of rhamnosyl and galactosyl residues by mild CF3CO2H treatment. Purified endoV from T. viride was able to act on the backbone of the polymer, but only if rhamnosyl substituents and phosphate had been removed. After complete removal of phosphate and partial removal of rhamnosyl residues by HF treatment, incubation with endoV resulted in a homologous series of oligomers. Purification of these oligomers and subsequent characterisation by NMR demonstrated that endoV was able to cleave the beta-(1-->4) linkage between two glucopyranosyl residues when the galactopyranosyl residue towards the nonreducing end is unsubstituted. The mode of action of endoV on HF-treated EPS B40 is discussed on the basis of the subsite model described for endoV [J.-P. Vincken, G. Beldman, A.G.J. Voragen, Carbohydr. Res., 298 (1997) 299-310].