Interaction of odorous lactones with phospholipids: Implications in toxicity towards producing yeast cells

Some lactonic aroma compounds, that can be produced industrially by microorganisms, become toxic towards the producing cells as these compounds reach high concentrations in the culture medium. To determine the manner by which these metabolites may influence yeast physiology, the effects of four lactones (concentration range of 100 to 300 mg l-1) on the growth of Yarrowia lipolytica and on the phase behaviour of deuterated dimyristoylphos-phatidylcholine (DMPC-d27) were studied. The results showed that the hydrophobic lactones decrease the phase transition temperature (Tm) of DMPC-d27 bilayers and that Tm decrease (ΔTm) was related to the inhibitory action of the lactones on yeast growth (evaluated by the lag time). These results suggest that whatever the lactone, a ΔTm of at least 2.5°C resulted in a total growth inhibition: this implicates the lactone-phospholipids interaction in the mechanism of yeast growth inhibition. The test used in the present study may be a predicting method to assess the in vivo action of potential membrane active compounds.