Oenococcus

This genus was established as recently as 1995, and contains only one species, O. oeni. Not surprisingly, O. oeni is located, phylogenetically, within the Leuconostocaceae branch; however, it is somewhat distant from Leuconostoc and Weissella (Figure 2-2). Although O. oeni shares many phenotypic properties with Leu-conostoc sp. (e.g., heterofermentative metabolism, mesophilic growth range), several important physiological differences exist. In particular, O. oeni is much more acid-tolerant than Leuconostoc as it is able to commence growth in media with a pH below 5.0. In addition, O. oeni is one of the most ethanol-tolerant of all lactic acid bacteria and can grow in the presence of 10% ethanol. In general, however, most strains of O. oeni are slow-growing and ferment a limited number of sugars.

As implied by the etymology of its name, the use of O. oeni in fermented foods is restricted to only one application, namely wine making (oenos is the Greek word for wine). Despite its limited use, however, the importance of O. oeni during the wine fermentation cannot be over-stated.This is because O. oeni has the ability to de-acidify wine via the malolactic fermentation, whereby malic acid is decarboxylated to lactic acid (described in detail in Chapter 10). Moreover, given the ability of O. oeni to fer

Table 2.3. Characteristics of Leuconostoc and Oenococcus1

Property

Leuconostoc mesenteroides subsp. cremoris mesenteroides dextranicum

Leuconostoc lactis

Oenococcus oeni

% G+C

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