title: Sub-optimal pH Preadaptation Improves the Survival ofLactobacillus plantarumStrains and the Malic Acid Consumption in Wine-Like Medium.
abstract: Forty-two oenological strains ofLb. plantarumwere assessed for their response to ethanol and pH values generally encountered in wines. Strains showed a higher variability in the survival when exposed to low pH (3.5 or 3.0) than when exposed to ethanol (10 or 14%). The study allowed to individuate the highest ethanol concentration (8%) and the lowest pH value (4.0) for the growth of strains, even if the maximum specific growth rate (μmax) resulted significantly reduced by these conditions. Two strains (GT1 and LT11) preadapted to 2% ethanol and cultured up to 14% of ethanol showed a higher growth than those non-preadapted when they were cultivated at 8% of ethanol. The evaluation of the same strains preadapted to low pH values (5.0 and 4.0) and then grown at pH 3.5 or 3.0 showed only for GT1 a sensitive μmaxincrement when it was cultivated in MRS at pH 3 after a preadaptation to pH 5.0. The survival of GT1 and LT11 was evaluated in Ringer's solution at 14% ethanol after a long-term adaptation in MRS with 2% ethanol or in MRS with 2% ethanol acidified at pH 5.0 (both conditions, BC). Analogously, the survival was evaluated at pH 3.5 after a long-term adaptation in MRS at pH 5.0 or in MRS BC. The impact of the physiologic state (exponential phasevsstationary phase) on the survival was also evaluated. Preadapted cells showed the same behavior of non-preadapted cells only when cultures were recovered in the stationary phase. Mathematical functions were individuated for the description of the survival of GT1 and LT11 in MRS at 14% ethanol or at pH 3.5. Finally, a synthetic wine (SW) was used to assess the behavior ofLb. plantarumGT1 and LT11 preadapted in MRS at 2% ethanol or at pH 5.0 or in BC. Only GT1 preadapted to pH 5.0 and collected in the stationary phase showed constant values of microbial counts after incubation for 15 days at 20°C. In addition, after 15 days the L-malic acid resulted completely degraded and the pH value increased of about 0.3 units.
authors.affiliation: Department of Agricultural, Environmental and Food Sciences (DiAAA), University of Molise Campobasso, Italy.
authors.forename: Mariantonietta
authors.initials: M
authors.lastname: Succi
authors.affiliation: Department of Agricultural, Environmental and Food Sciences (DiAAA), University of Molise Campobasso, Italy.
authors.forename: Gianfranco
authors.initials: G
authors.lastname: Pannella
authors.affiliation: Department of Agricultural, Environmental and Food Sciences (DiAAA), University of Molise Campobasso, Italy.
authors.forename: Patrizio
authors.initials: P
authors.lastname: Tremonte
authors.affiliation: Department of Agricultural, Environmental and Food Sciences (DiAAA), University of Molise Campobasso, Italy.
authors.forename: Luca
authors.initials: L
authors.lastname: Tipaldi
authors.affiliation: Department of Agricultural, Environmental and Food Sciences (DiAAA), University of Molise Campobasso, Italy.
authors.forename: Raffaele
authors.initials: R
authors.lastname: Coppola
authors.affiliation: Department of Agricultural, Environmental and Food Sciences (DiAAA), University of Molise Campobasso, Italy.
authors.forename: Massimo
authors.initials: M
authors.lastname: Iorizzo
authors.affiliation: Department of Agricultural, Environmental and Food Sciences (DiAAA), University of Molise Campobasso, Italy.
authors.forename: Silvia Jane
authors.initials: SJ
authors.lastname: Lombardi
authors.affiliation: Department of Agricultural, Environmental and Food Sciences (DiAAA), University of Molise Campobasso, Italy.
authors.forename: Elena
authors.initials: E
authors.lastname: Sorrentino
keywords: cross-resistance; ethanol; malolactic fermentation; pH; wine