Identification of dominant lactic acid bacteria isolated from grape juices. Assessment of its biochemical activities relevant to flavor development in wine

Fabiana Maria Saguir^1,3, Iris Eleonora Loto Campos¹, Carmen Maturano¹, Maria Cristina Manca de Nadra^1,2,3

¹Facultad de Bioquímica, Química y Farmacia, Universidad Nacional de Tucumán, Tucumán, Argentina; ²Centro de Referencia para Lactobacilos (Cerela), Tucumán, Argentina; ³Career Investigators from Consejo Nacional de Investigaciones Científicas y Técnicas, Argentina

Abstract: We investigated the dominant lactic acid bacteria (LAB) from grape juice and commencement of malolactic fermentation (MLF) samples of a cellar located in Argentina and assessment of its β-glucosidase activity and butter aroma compounds production. LAB number found in grape juice (approximately log₁₀ 3.3) was lower than that obtained in the MLF samples. Oenococcus oeni was predominant, accounting for 68% of the 81 LAB isolated. Majority of whole cells derived from O. oeni cultures at the end of the exponential growth showed detectable β-glucosidase activity. Contrarily, the highest proportion of them did not produce diacetyl, acetoin, and 2,3-butylene glycol. A direct relation between both properties among the O. oeni strains could not be established. In the selected MS25 strain, L-malic acid was compatible with good enzyme activity and was partially able to annul the negative influence of the low pH (3.8). In different conditions, the aroma compounds were lower than 4 mg/ml, especially at pH 3.8 and in presence of L-malic acid (2.5 g/l). This strain could have adequate characteristics for potential use in winemaking. Finally, the assessment of both biochemical properties in O. oeni should be considered as a quality criterion for selecting starter cultures for the improvement of the wines aroma.

Keywords: isolation, lactic acid bacteria, biochemical properties, aroma, wine