EFFECT OF PHYSICO-CHEMICAL FACTORS INVOLVED IN WINEMAKING ON THE GROWTH AND METABIOLIC BEHAVIOR OF O. oeni AND YEASTS BY USING A SURFACE RESPONSE METHOD

ALE, C. E.; PASTERIS, S.E.; BRU, E.; MORATA, V; STRASSER DE SAAD, A.M.

Simposio; IV SIMPOSIO INTERNACIONAL DE BACTERIAS LÁCTICAS (SIBAL) ALIMENTOS, SALUD Y APLICACIONES.; 2013

The growth and persistence of microbial populations related to winemaking depend on the specific strain characteristics, the culture conditions and the additives supplementation. The last one improves the selective pressure and therefore the metabolic profile of the starter cultures. To select the optimal culture condition at laboratory scale, it is necessary to perform multi-factorial analyses that allow establishing the appropriate combination of the main physico-chemical parameters involved in winemaking: temperature, pH and SO2 concentration. Thus, a surface response design was used to evaluate their effect on cell viability (CFU/mL) and metabolic behavior of mixed culture of Saccharomyces (S.) cerevisiae mc2, Kloeckera apiculata mF and Oenococcus (O.) oeni X2L (potentially starter cultures). Natural Grape Juice medium supplemented with Tween 80 (NGJ-T) was inoculated with 106 CFU/mL of each strain. Media were incubated at different temperatures (26, 28, 30ºC), pH (3.5, 4.5, 5.5) and SO2 concentrations (50, 100, 150 mg/L) during 6 days. Supernatant fractions (1.5 mL) were collected by centrifugation for analytical determinations. The strains grew in all the culture conditions, but mainly when low SO2 concentration was added. Overall, at 3 day, yeasts were the predominant microorganisms reaching maximum biomass of 5 x 1010 CFU/mL, S. cerevisiae being the most environmental conditions-tolerant strain, while O. oeni reached 1 x 107 CFU/mL. According to the statistical method used, an interaction between the three physic-chemical factors was observed to affect both substrates consumption and products formation. Specifically, the effect of each factor was different for each level of the others affecting the microbial metabolic behavior. The system showed high malic acid consumption (2.6 mM) and desirable sugar utilization ( 80 mM) when the strains were grown at pH 5.5. The microbial metabolic behavior at different SO2 concentration showed a variable response associate with changes in temperature of incubation. Thus, glucose and pentoses consumption was highly modified at different SO2 concentrations, however slightly fructose consumption was detected. Moreover, at low SO2 concentrations and temperatures range, malic acid was completely used. Considering this last aspect, the best conditions to obtain high glycerol (1.8 mM) and low acetate (