Selection of Oenococcus oeni Strains as Starter Cultures of Malolactic Fermentation in Wines from Tucuman, Argentina
Jose Martinez-Chamas, Maria Cristina Rubio, and Pedro Aredes-Fernandez*
*Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET) and Facultad de Bioquímica, Química y Farmacia, Universidad Nacional de Tucumán, Ayacucho 471, San Miguel de Tucuman, Tucuman 4000, Argentina (firstname.lastname@example.org)
Malolactic fermentation is a desirable process carried out in red wines by lactic acid bacteria, mainly Oenococcus oeni, that lowers acidity, improves wine quality, and contributes to microbiological stability. Only bacteria well-adapted to adverse wine conditions can perform this process and are selected as possible candidates for starter cultures. Some technological properties of O. oeni isolates were evaluated, including adaptation to different unfavorable wine conditions and consumption of different carbon sources. Lactic acid bacteria were isolated from red wine from Colalao del Valle-Tucumán. The tolerance of 22 isolates identified as O. oeni to stressful wine conditions was assayed, determining growth as absorbance at 560 nm in MLO medium at different pH values (3.5, 3.7, and 4.0), ethanol concentrations (12 and 14%), and sodium metabisulfite concentrations (40, 80, and 160 mg/L). In addition, consumption of malic acid, glucose, and fructose were evaluated in MLO medium supplemented with L-malic acid, determining bacterial growth by counting cells spread on MLO agar. The O. oeni isolates designated RAM1 and RAM10 showed the greatest tolerance to stress conditions in wine. All isolates completely consumed the L-malic acid in the first 24 hr and consumed all glucose and fructose at 48 hr, reaching a population of 108 to 109 CFU/mL. The isolates RAM1 and RAM10 could be used as starter cultures due to their tolerance of stress conditions and ability to consume L-malic acid. This study establishes a basis to develop possible starter cultures well adapted to the ecological conditions of wines from Colalao del Valle, ensuring implantation in the natural environment.
Funding Support: CONICET – Project 2014-627