Effect of acclimation medium on cell viability, membrane integrity and ability to consume malic acid in synthetic wine by oenologicalLactobacillus plantarumstrains

Abstract

Aims: The aim of this work was to evaluate the effect of acclimation on the viability, membrane integrity and the ability to consume malic acid of three oenological strains of Lactobacillus plantarum. Methods and Results: Cultures in the stationary phase were inoculated in an acclimation medium (Accl.) containing 0, 6 or 10% v/v ethanol and incubated 48 h at 28°C. After incubation, cells were harvested by centrifugation and inoculated in a synthetic wine, containing 14% v/v ethanol and pH 3Á5 at 28°C. Viability and membrane integrity were determined by flow cytometry (FC) using carboxyfluorescein diacetate (cFDA) and propidium iodide. Bacterial growth and malic acid consumption were monitored in a synthetic wine during 15 days. In nonacclimated strains, the damage of bacterial membranes produced a dramatic decrease in microbial viability in synthetic wine. In contrast, survival of strains previously acclimated in Accl. with 6 and 10% v/v ethanol was noticeable higher. Therefore, acclimation with ethanol increased the cultivability in synthetic wine and consequently, the consumption of L-malic acid after 15 days of growth. Conclusion: Acclimation of oenological strains in media containing ethanol prior to wine inoculation significantly decreases the membrane damage and improves viability in the harsh wine conditions. The role of membrane integrity is crucial to warrant the degradation of L-malic acid. Significance and Impact of the Study: The efficiency of multiparametric FC in monitoring viability and membrane damage along with the malic acid consumption has a strong impact on winemaking because it represents a useful tool for a quick and highly reliable evaluation of oenological parameters.

Effect of the fatty acid composition of acclimated oenological L actobacillus plantarum on the resistance to ethanol

“…§Initial inoculum 1 9 10 7 CFU ml À1 . ¶Results previously reported in Bravo-Ferrada et al 2014. The relationship between resistance to ethanol and increase of the short-length fatty acid reflects the complexity of the mechanisms involved. van Bokhorst-van de Veen et al (2011) reported that ethanol stress affects the expression of Lact.…”

“…To investigate the influence of fatty acid composition on the technological properties of strains, the alterations occurred upon acclimation were correlated with the viability and MAC previously reported (Bravo-Ferrada et al 2014). The log CFU ml À1 reported in Table 1 corresponds to the viability of strains after 15 days of incubation at 28°C (initial inoculum:~10 7 CFU ml À1 ).…”

“…It was also reported that acclimation of Lact. plantarum leads to decrease in membrane damage when grown in the presence of ethanol (Bravo-Ferrada et al 2014). Lipid membranes are the main target of damage by ethanol and micro-organisms have different strategies to prevent this damage (da Silveira et al 2003, Silveira et al 2004.…”

“…plantarum with 6 and 10% v/v ethanol prevents membrane damage after inoculation in wine conditions (Bravo‐Ferrada et al . ). However, to our knowledge, the effect of acclimation on the fatty acid composition of Lact.…”

Sub-optimal pH Preadaptation Improves the Survival of Lactobacillus plantarum Strains and the Malic Acid Consumption in Wine-Like Medium

“…plantarum to survive to specific stress factors encountered in wine (e.g., acid pH, cold), as well as other stress factors in various foods (e.g., bile, osmotic, heat, high pressure) was widely explored (van de Guchte et al, 2002; De Angelis and Gobbetti, 2011). Moreover, in recent years some Authors (Bravo-Ferrada et al, 2013, 2014, 2015, 2016) reported the positive effect of acclimation to ethanol concentrations lower than that of wine on the viability and malic acid consumption of oenological Lb. plantarum strains.…”