Yeast is a fungus used in the production of bread and ethanol.
It can be bred by setting apart a little bit (called sourdough) of each batch of bread dough and mixing that into the next batch. Fresh yeast will survive about 7-10 days in a common screwtop jar and can be frozen for an extended period. Commercially available packets of dried yeast will remain viable for about three months.
- How long will frozen yeast remain viable in a spacecraft environment?
- J. Seymour - The concise guide to self-sufficiency 2007. ISBN 978-1-4053-2020-7 p. 156.