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The early death of two non-Saccharomyces wine strains (H. guilliermondii and H. uvarum) during mixed fermentations with S. cerevisiae was studied under enological growth conditions. Several microvinifications were performed in synthetic grape juice, either with single non-Saccharomyces or with mixed S. cerevisiae/non-Saccharomyces inocula. In all mixed cultures, non-Saccharomyces yeasts grew together with S. cerevisiae during the first 1-3 days (depending on the initial inoculum concentration) and then, suddenly, non-Saccharomyces cells began to die off, regardless of the ethanol concentrations present. Conversely, in both non-Saccharomyces single cultures the number of viable cells remained high (ranging 10(7)-10(8) CFU ml(-1)) even when cultures reached significant ethanol concentrations (up to 60-70 g l(-1)). Thus, at least for these yeast strains, it seems that ethanol is not the main death-inducing factor. Furthermore, mixed cultures performed with different S. cerevisiae/ H. guilliermondii inoculum ratios (3:1; 1:2; 1:10; 1:100) revealed that H. guilliermondii death increases for higher inoculum ratios. In order to investigate if the nature of the yeast-yeast interaction was related or not with a cell-cell contact-mediated mechanism, cell-free supernatants obtained from 3 and 6 day-old mixed cultures were inoculated with H. guilliermondii pure cultures. Under these conditions, cells still died and much higher death rates were found for the 6 days than for the 3 day-old supernatants. This strongly indicates that one or more toxic compounds produced by S. cerevisiae triggers the early death of the H. guilliermondii cells in mixed cultures with S. cerevisiae. Finally, although it has not been yet possible to identify the nature of the toxic compounds involved in this phenomenon we must emphasise that the S. cerevisiae strain used in the present work is killer sensitive with respect to the classical killer toxins, K1, K2 and K28, whereas the H. guilliermondii and H. uvarum strains are killer neutral.

A total of 192 lactic acid bacteria were isolated from 2 types of naturally fermented dry sausages at 3 different stages of the ripening process in order to select the most suitable strains as starter cultures in dry-cured sausage manufacture according to their technological characteristics such as glucose fermentation, lactic and acetic acid production, and proteolytic, lipolytic, and antimicrobial activities. Identification of the isolates revealed that 31.2% were Pediococcus pentosaceus, 26.9% Lactococcus lactis, 18.6% Pediococcus acidilactici, 17% Lactobacillus brevis, and sporadic isolates of Leuconostoc mesenteroides, Lactobacillus plantarum, and Lactobacillus curvatus. Most of the strains did not produce gas from glucose and showed the capacity to produce lactic acid rapidly. Some 25% of the strains were able to degrade tributyrin (esterase activity), but none showed lipolytic activity against olive oil and pork fat. Only 3 strains of P. acidilactici showed weak proteolytic activity against myofibrillar or sarcoplasmic proteins. Also, the same strains showed antimicrobial activity against Listeria monocytogenes. Nine strains with the best properties were preselected and tested for biogenic amine production. The results showed that two of the strains, identified as P. acidilactici by polymerase chain reaction, had the potential to be further tested as starter cultures in pilot processing of Iberian sausages.

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