Saccharomyces
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| Genus: | Saccharomyces
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Saccharomyces is a genus in the kingdom of fungi that includes many species of yeast, the name Saccharomyces meaning 'sugar yeast'. The inability to utilize nitrate and ability to ferment various carbohydrates are typical characteristics of Saccharomyces. Colonies can grow and mature in 3 days and exhibit a yellow-tan colour. Many members of this genus are considered very important in food production. One example is Saccharomyces cerevisiae, which is used in making wine, bread, and beer. Other members of this genus include Saccharomyces bayanus, used in making wine, and Saccharomyces boulardii, used in medicine. More recently, Saccharomyces boulardii has been shown to be a sub-species of Saccharomyces cerevisiae.
Brewing yeast are polyploid and belong to the Saccharomyces genera. The brewing strains can be classified into two groups; the ale strains (Saccharomyces cerevisiae, generally used for ale and stout) and the lager strains Saccharomyces pastorianus also known as Saccharomyces cerevisiae, Saccharomyces carlsbergensis or Saccharomyces uvarum). Lager strains are a hybrid strain of Saccharomyces cerevisiae (ale strains) and Saccharomyces bayanus (wine strains) and are often referred to as bottom fermenting. In contrast, ale strains are referred to as top fermenting strains, reflecting their separation characteristics in open square fermenters. Although the two species differ in a number of ways including their response to temperature, sugar transport and utilisation, the Saccharomyces pastorianus and Saccharomyces cerevisiae species are closely related within the Saccharomyces genus.
The presence of yeast in beer was first suggested in 1680, although the genus was not named Saccharomyces until 1837. It was not until 1876 that Louis Pasteur demonstrated the involvement of living organisms in fermentation and in 1888, Hansen isolated brewing yeast and propagated leading to the importance of yeast in brewing. The use of microscopes for the study of yeast morphology and purity was crucial to understanding their functionality.
Saccharomyces can form symbiotic matricies with bacteria, and are used to produce kefir and ginger beer.
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