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SUMMARY: Osmophilic yeasts are found in the film of molasses on the crystals of raw sugars and in intermediate sugar-refining products of a wide range of concentration. They are allied to yeasts found in similar situations such as concentrated fruit juices, etc., and can be made to spore more or less freely under dry conditions, usually with conjugation. They are unable to destroy sucrose in strongly buffered solutions; some are able to produce sufficient acid from traces of invert sugar present gradually to invert the sucrose. During this process multiplication takes place. Previous workers have shown that the majority of organisms of this group is highly acid resistant.
Organisms which grow in a wide range of concentration of dissolved solids (salts, sugar) show, at acid pH values, an adaptation to growth in higher concentrations accompanied by a diminished metabolic rate. This is lost after a period of 6· 8 weeks in dilute media, but can be revived in many cases by increasing the sugar concentration in not less than two steps. Temperature resistance is also increased in concentrated media.