To determine the influence of the physiochemical environment on yeasts the growth in media with different starting pH valueswas examined. Z. florentina showed its pH optimum for reproduction after 72 h incubation at a starting pH 4 (end OD590 2.9), whereas starting pH 3 decreased growth of Z. florentina (OD590 1.8). Higher starting pH-values, from 5 to 8, displayed similar influence on growth, the OD590 of Z. florentina rose to 2.6. S. cerevisiae was not influenced by acidification of the medium.