Torula species

Lactose-fermenting yeasts have been known for some time, but their use to produce ethyl alcohol and yeast from whey received serious attention only much later. Certain Torula species yield more alcohol than might have been expected from statements in the literature. Four kefir yeasts, two Torula species, one of Torulopsis and one additional yeast species, produced alcohol yielding 68 to 80% of the theoretical quantity. A maximal yield, 80.3%, based on a theoretical yield of 4 moles of alcohol per mole of lactose fermented, was obtained with a strain of Torula cremoris in a 21.7-hr fermentation at 30 to 32°C (Marth 1974). 

Torula species, as with most yeasts, are separated from one another largely by chemical means. "... 

Antimicrobial action. The action of propionic acid is directed mainly against moulds. Yeasts are likewise inhibited, and so also are some gram-negative bacteria. Some yeasts (e. g. torula species), are capable of utilizing propionic acid in their metabolism. Inhibition of E. coli may be reversed with addition of B-alanine, indieating that propionates interferes with B-alanine synthesis (Doores, 1993). In general the action of propionic acid is weak in comparison with other preservatives from the organic acid type (Heseltine, 1955). 

Other workers including Jakubowski et. al. (1983) have found many different yeast and mould contaminants comprising most of the well known biodeteriogenic species such as Aspergillus, Fusarium, Geotrichum, Penicillium, Scopulariopsis, Saccharomyces and Torula. In addition, the author has also isolated Rhodotorula and Sporobolornyces on a number of occasions. 

Yeast autolysates may be obtained from waste yeasts from breweries and dairies. If specific flavour types are required also cultured yeasts and yeast lines with special properties are used (species Saccharomyces, Torula). 

Saprophytic, common. Many thermophilic species participate in the decomposition of straw and manure in the making oL mushroom composts. Although Torula is rarely seen in agar culture, its cousin Rhodotorula, a red yeast, is frequently seen. 

Yeast is a microscopic, unicellular organism of which there are several hundred species, only a very few of which are of commercial importance, namely, Saccha-romyces cerevisiae, Saccharomyces carlsbergensis, Candida utilis (formerly Torula utilis), Candida tropicalis, and Kluyveromyces fragilis. Selected Saccharomyces spp. are used for the production of wines and other alcoholic beverages. 

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