Effect of lactic acid on the growth dynamics of Candida maltosa YP1

The growth dynamics of the oxidative imperfect yeast strain Candida maltosa YP1 isolated from the surface of fruit yoghurt was studied in relation to the lactic acid concentration ranging from 0 to 1.6% (w/v). The maximal specific growth rate of 0.36 h-1 and minimal lag-phase duration of 2.9 h were found in the glucose solution without lactic acid at 25°C. The decrease of the natural logarithm of both the specific growth rate (ln µ) and the lag-phase prolongation (ln ) in the dependence on the increase of lactic acid concentration (0-1.59%) was significantly linear (ln µ = -1.1458 - 0.6056 c; R2(µ) = 0.9526; ln l = 1.0141 + 1.9766 c; R2() = 0.9577). Based on these equations, the prediction of the time necessary for C. maltosa YP1 to reach 1 × 106 CFU/ml in the dependance on lactic acid concentration and, the initial density of the yeast culture was calculated. For example, C. maltosa YP1 was able to reach the level of 1 × 106 CFU/ml in a model glucose solution at the initial concentration N0 = 1 CFU/ml, 0.9% lactic acid and 25°C within 2 d. The growth predictions presented indicate a considerable resistance of C. maltosa YP1 to lactic acid in the concentration of up to 1.3% (w/v).