Aims: To assess glycosidase activities from a range of Lactobacillus and Pediococcus species and characterize these activities under conditions pertinent to the wine industry.
Methods and results: Lactic acid bacteria were cultured in MRS broth supplemented with apple juice before being harvested, washed and assayed for glycosidase activity using p-nitrophenol-linked substrates. All strains exhibited a detectable capacity for the hydrolysis of the beta- and alpha-d-glucopyranosides. The magnitude of these activities and their response to the physico-chemical parameters investigated varied in a strain-dependent manner. The use of an assay buffer with a pH below 4 generally resulted in a reduced hydrolysis of both substrates while temperature optima ranged between 35 and 45 degrees C. The effect of the inclusion of ethanol in the assay buffer (up to 12%, v/v) ranged from near complete inhibition to increases in activity approaching 80%. With the clear exception of a single strain, glucose and fructose (0.1-20 g l(-1)) acted as inhibitors. An assessment of glycosidase activity during simultaneous exposure to glucose and ethanol at a pH of 3.5 suggested that ethanol decreased loss of activity under these wine-like conditions.
Conclusions: Lactobacillus spp. and Pediococcus spp. possess varying degrees of beta- and alpha-d-glucopyranosidase activities, which in turn are influenced differently by exposure to ethanol and/or sugars, temperature and pH. Several strains appeared suited for further evaluation under winemaking conditions.
Significance and impact of the study: This work highlights the fact that strains of Lactobacillus and Pediococcus have the potential to influence the glycoside composition of wine. Tailoring of wine may therefore be possible through selective application of strains or enzymatic extracts thereof.