EFFECT OF KILLER YEASTS ON RELEVANT WINE LACTIC ACID BACTERIA

MIGUEL FERNÁNDEZ DE ULLIVARRI; LUCÍA M. MENDOZA; RAÚL R. RAYA

San Miguel de Tucumán

Simposio; IV Simposio Internacional de Bacterias Lacticas (SIBAL) Alimentos, Salud y Alimentos; 2013

During wine-making process different microbial groups, mainly yeasts and bacteria, interact influencing on the quality of the final product. Killer yeasts produce proteinaceous toxins that may inhibit the growth of spoilage yeasts and fungi, but their effect on lactic acid bacteria (LAB) is not well characterized. Oenococcus oeni is the principal LAB used as wine starter culture for malolactic fermentation. However, other LAB species as Lactobacillus hilgardii are capable to produce biogenic amines, compounds regarded as antinutritional factors. In this study we evaluated the effect of killer yeast supernatants on growth and metabolism of O. oeni X2L and L. hilgardii 5w (a histamine producer). Killer supernatants were prepared in YPD broth (pH 4.0, 20 ºC, 72 h) incubating the selected killer strains Saccharomyces cerevisiae Cf8 and Pichia anomala Cf20 in single and mixed cultures. Control media was prepared inactivating Cf20 killer toxin by heating the supernatant at 100 ºC for 30 min. Supernatants were supplemented with BM broth + histidine 10x (with bromophenol blue, pH 4.0) or MRS + malic acid 10x for L. hilgardii 5w and O. oeni X2L, respectively. Bacteria were inoculated at 5 and 10% respectively and then incubated at 30 ºC. Bacterial growth was followed by OD560 measurements. Malic acid consumption by O. oeni X2L was evaluated using an enzymatic method. Histamine production by L. hilgardii 5w was qualitatively determined by color turn of bromophenol blue from green to yellow. O. oeni X2L did not show growth differences in killer supernatants compared to control. This strain showed short lag phases in all supernatants while malic acid consumption rates were 91, 99 and 86% compared to control for Cf8, Cf20 and Cf8-Cf20 supernatants, respectively. Nevertheless, malic acid was completely depleted from all media at 24 h of incubation. Regarding L. hilgardii 5w, killer supernatants produced a longer lag phase, lower final growth and lower histamine production compared to control. We conclude that Cf8 and Cf20 killer toxins would have an inhibitory effect on the histamine producer strain, L. hilgardii 5w, whereas growth and malolactic activity of O. oeni X2L would not be affected. The results obtained in this study could indicate a new positive characteristic of killer yeasts (S. cerevisiae Cf8 and P. anomala Cf20) as biocontrol agents for wine-making process.