Maintenance and Culture of Yeasts

Yeasts generally are very easy to maintain, store, cultivate in almost any size of batch, and isolate from most habitats, but if a few elementary methods are understood, their isolation, storage, and culture, for day-to-day use in the laboratory is greatly simplified. Furthermore, the same methods can be used for maintenance of a stock collection for use in a production plant in a yeast-based industry. Being a group of unicellular organisms, yeasts can be handled in the same way as most bacteria, except that their nutritional and environmental requirements are, with few exceptions, much simpler. The techniques used will be considered under the following headings:

1.	For short-term maintenance, for daily use. Rich, media, such as yeast extract-peptone-glucose agar, YM agar, or malt agar, are commonly used (see Section 3. );
2.	For medium-term storage;
3.	For long-term preservation, as in a culture collection, where immediate access is less important, but maintenance of the characteristics of the species and strain is the primary objective; and
4.	Methods for cultivation of yeasts, in small-, medium-, and large-scale volumes.