EFFECTS OF PH, TEMPERATURE, ETHANOL, AND MALATE CONCENTRATION ON LACTOBACILLUS-PLANTARUM AND LEUCONOSTOC-OENOS - MODELING OF THE MALOLACTICACTIVITY

The effects of several chemico-physical factors (pH, SO2, and ethanol concentration) on the growth and malolactic activity of Lactobacillus plantarum and Leuconostoc oenos strains, isolated from different Itali an red wines, were evaluated. A large individual variability of stress resistance was observed within the two species. The isolates of L. pl antarum showed, under the various conditions better growth performance s with respect to Leuc. oenos. Ethanol and malic acid concentration, t emperature, pH, and inoculum size were modulated according a Central C omposite Design (CCD). Two representative strains of each of the two s pecies were individually grown in the various combinations of the CCD, and their activity was evaluated by gas chromatograph on the basis of the CO2 concentration in the head space of sealed vials. The malolact ic activity of the various runs were modelled according to the Gompert z equation. The Gompertz parameters, mu(max) and length of lag phase, were calculated in order to obtain polynomial equations. The compariso n of the models obtained indicated that different factors limit the ac tivities of the two species and that L. plantarum is more resistant to the combined action of various stresses. Having revealed a weaker dep endence on the medium modifications as well as higher decarboxylation performances, L. plantarum can be considered as a more efficient alter native to Leuc. oenos for the induction of malolactic fermentation in musts.