Cell membrane damage induced by phenolic acids on wine lactic acid bacteria

Phenol-derived compounds are known to have membrane-active properties against microorganisms causing leakage of cell constituents including proteins, nucleic acids, ATP, and inorganic ions (such as potassium or phosphate). Phenolic (hydroxybenzoic and hydroxycinnamic) acids are components of the highly complex phenolic composition of wines. In this work, several wine-occurring phenolic acids, that were previously found to affect the growth and the survival of certain wine lactic acid bacteria, were tested for their effects on the cell membrane of these same strains. Selected strains of Lactobacillus hilgardii and Oenococcus oeni were cultivated to late exponential phase and then centrifuged, washed, and resuspended in buffer solution. Phenolic acids were added to the cell suspensions to induce chemical stress. Potassium leakage from cells was measured by determining the extracellular potassium concentration of the medium using a potassium ion-sensitive electrode. A combined glass electrode was used to monitor pH changes. Phosphate efflux was determined using a flow injection analysis (FIA) system with spectrophotometric detection. Samples were collected at regular intervals, microfiltered, and injected in the FIA system. Results indicate that p-coumaric acid had the strongest effect of all phenolic acids, causing rapid potassium and phosphate leakages from cells after exposure to this compound. Generally, hydroxycinnamic acids induced faster leakage rates than hydroxybenzoic acids, which could be related to their higher lypophilic character. These results agree with previous growth and survival experiments. The differences of phenolic acids toxicity toward lactic acid bacteria seem to be related to their effects on membrane permeability.