Each microbial culture was transferred individually to 5 ml of deMan Rogosa Sharpe medium (MRS broth, Difco) for lactic acid bacteria, Tryptic soy broth (TSB, Difco) for other bacteria and Saboraud dextrose broth (SDB, Difco) for yeasts. Cultures of bacteria and yeasts were incubated at 37 and 30° C for 24 and 72 h, respectively. The microbial cells were harvested by centrifugation at 3000 rpm for 15 min, washed twice and resuspended in 0.1% peptone water. Turbidity was adjusted to match that of 5 McFarland standard (0.5 for yeasts) to obtain a cell concentration of 107 CFU/ml.