Evaluation of Bifidobacterium spp. for the production of a potentially probiotic malt-based beverage

A malt hydrolisate mimicking the composition of that produced in a brewery by the infusion method has been evaluated as a potential substrate for fermentation by bifidobacteria with the aim of producing a potentially probiotic beverage. Preliminary experiments indicated the need for addition of a growth promoter to the malt hydrolisate, and yeast extract in a concentration of 10 g l−1 was chosen. The growth of four Bifidobacterium spp. in the malt hydrolisate with 10 g l−1 of yeast extract was followed over a 24 h period at 37 °C. The results showed an increase in bacterial population between 1.5 and 2.0 log10 cycles with a maximum growth rate of approximately 0.2 h−1. Large amounts of sugars and free amino nitrogen are still present at the beginning of the stationary phase of growth. The end of the exponential phase was attributed to the accumulation of toxic metabolites combined with the low pH.