Irina Kristof, Nancy Roxana Vera, and Pedro Adrián Aredes Fernández*
*Universidad Nacional de Tucumán, Ayacucho 471 San Miguel de Tucumán, Tucumán, Argentina, 4000, Argentina (pedroaredes@hotmail.com)

Oenococcus oeni can develop adaptation mechanisms to avoid nutritional stress, such as the release of proteases. These proteases release peptides and amino acids that help maintain bacterial viability, necessary for a successful malolactic fermen­tation (MLF). Pasteurized apple juice was fermented with a strain of Saccharomyces cerevisiae and then divided into two batches. One batch was centrifuged, filtered, and pasteurized. The other was reserved without pasteurization (lees batch). Both batch­es were used to perform the MLF with three strains of O. oeni. Strains RAM10 and RAM11 were isolated from Argentinean Malbec wine. Strain VP41 was purchased from Lallemand. Both batches of fermented apple juice were individually inoculated with the three strains of O. oeni. Bacterial viability was determined by colony count in MLO agar. Cell concentration was determined by measuring absorbance. Malic acid con­centration was determined enzymatically. Supernatants obtained at different times were used to determine proteins (Bradford method) and peptides, amino acids, and proteolytic activity (ninhydrin reagent by Doi method). During MLF, the three strains maintained viability at 107 to 108 CFU/mL. The presence of lees did not modify malic acid consumption by the RAM10 and VP41 strains; however, an improvement in this parameter was detected in the RAM11 strain. Without lees, any bacterial proteolytic activity detected derives from protein breakdown, evidenced by increased concen­trations of peptides and amino acids during MLF. Peptide release was not detected in the media with lees. The maximum proteolytic activity of the studied strains occurred after 24 hrs MLF, in the presence or absence of lees, but greater in the absence of lees.

Funding Support: CONICET Consejo Nacional de Investigaciones Científicas y Técnicas