Apiculate yeasts

Indeed, grapes are a primary source of microorganism, and many studies have shown that natural fermentation starts with those species predominant on grapes at harvest time (Fleet et ah, 2002). These can include the apiculate yeasts (Hanseniaspora uvarum and Kloeckera apicu-lata), Metschnikozvia, Candida, Pichia, Khodotorula, and Kluyveromyces. In contrast, although it is the main wine fermentation yeast, Saccharomyces have only rarely been isolated from vineyards (Martini, 1993 Martini et ah, 1996 Pretorius, 2000 Sabate et ah, 1998), since it is closely associated with the winery environment (Ciani et ah, 2004). 

During traditional winemaking in October, endogenous yeasts are very active and their action may need to be limited by appropriate additions of sulfur dioxide. Usually spontaneous fermentation begins with apiculate yeasts of the genus Hanseniaspora. However, their extended... 

Gil, J. V, Mateo, J. J., Jimenez, M., Pastor, A., Huerta, X. (1996) Aroma compounds in wine as influenced by apiculate yeasts. Journal of Food Science, 61, 1247-1249. 

Acetic acid represents the only organic acid of normal olfactory sensory significance to wines (27). While acetic acid may be formed by . cerevisiae, the concentrations produced are typically less than 300 mg/L (55), far lower than the concentrations produced by spoilage microorganisms (he, Acetobacter) which are the predominate source (52). Apiculate yeasts may also serve as a source of acetic acid Romano et ah (36) found that Kl apiculata typically produced greater than 200 mg/L acetic acid in synthetic medium fermentations. 

Many varieties of this yeast occur, similar in degree to those of S. ellipsoideus. They are widely distributed in nature, occurring on most fruits, and are particularly abundant on acid fruits such as grapes. Apiculate yeast appears on the partially ripe grapes before the true wine yeast and even on ripe grapes is more abundant than the latter. The rate of multiplication of this yeast... 

Wines in which the apiculate yeast has had a large part in the fermentation are apt to retain some un fermented sugar and are very liable to the attacks of disease organisms. Their taste and color are defective, often suggestive of cider, and they are difficult to clear. This yeast attacks the fixed acids of the must, the amount of which is therefore diminished in the wine while, on the other hand, the volatile acids are increased. 

It is generally accepted that in the case of sound fruit, population density and diversity of native (formerly referred to as wild ) yeasts is limited, ranging from less than 10 to 10 CFU/berry. The most frequently isolated native species are the so-called apiculate yeasts, Kloeckera apiculata, and its sexual counterpart, Hanseniaspora uvarum. These lemon-shaped small yeasts get their name from repeated budding at both poles (see Fig. 3-1) and often account for over 50% of the total yeast flora recovered from fruit. 

Yeasts exhibit several types of budding which may be of diagnostic value. Among those isolated from fermenting and aging wine, multilateral (characteristic of Saccharomyces sp.) and restricted polar budding (characteristic of apiculate yeasts) are most frequendy observed. Occassionally, fission yeasts Schizosaccharomyces pombe) may be isolated. These reproduce by the formation of cross-walls which is visually similar to bacterial fission. 

CiANi, M. and F. Fatichenti. 1999. Selective sugar consumption by apiculate yeasts. Lett. Appl. Microbiol. 28 203-206. 

Species other than Saccharomyces, in particular apiculated yeasts (Hanseniaspora uvarum, Kloeckera apiculata), are present on the grape and are sometimes found at the beginning of fermentations. These species have fewer polymorphous karyotypes and fewer bands than in Saccharomyces. Versavaud et al. (1993) differentiated between strains of apiculated yeast species and Candida famata by using restriction endonucleases at rare sites (Not 1 and Sfl I). The endonucleases cut the chromosomes into a limited number of fragments, which were then separated by pulse-field electrophoresis. 

In the first hours of spontaneous fermentations, the first tanks filled have a very similar microflora to that of the grapes. There is a large proportion of apiculated yeasts and M. pulcherrima. After about 20 hours, S. cerevisiae develops and coexists with the grape yeasts. The latter quickly disappear at the start of spontaneous fennentation. In red winemaking in the Bordeaux region, as soon as must density drops below 1.070-1.060, the colony samples obtained by spreading out diluted must on a solid medium generally isolate exclusively S. cerevisiae (10 to 10 cells/ml). This species... 

In an unsulfited and non-inoculated must, contamination yeasts can begin to develop within a few hours of filling the tank. Apiculated yeasts (Kloechera, Hanseniaspora) are the most frequently encountered. Aerobic yeasts also develop (Candida, Pichia, Hansenula), producing acetic acid and ethyl acetate. Brettanomyces and its characteristic animal-like odors are rare in must. Although such yeasts can be relatively resistant to sulfur dioxide (Fleet, 1992), sulfiting followed by inoculating with a selected strain of Saccharomyces cerevisiae constitute, in practice, an effective means of avoiding contamination (Section 3.5.4). 

Hanseniaspora Apiculate yeast that show bipolar budding producing lemon shaped spores Used in sugar fermentations H. uvarum... 

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