Studies on Film-Forming Yeasts. Acid Production by Zygopichia And Zygohansenula

Abstract

Film-forming yeasts are of widespread occurrence and of considerable economic importance. Representatives belong to the sporogenous genera Pichia, Zygopichia, Hansenula, Zygohansenula, and Debaryomyces; and to the asporogenous genus Mycoderma. They are frequently found growing on salt brines used for the storage of various food products; Mrak and Bonar (1939) in a study of the taxonomy and salt tolerance of certain film yeasts include a good bibliography. Fermented beverages of many types have yielded new forms. In some cases a particular quality of the drink has been attributed to these yeasts (e.g., the flor of sherry, cf. Hohl and Cruess, 1939) while in other cases they have been looked upon as nuisances because of their ability to oxidize ethanol rapidly or to impart off-flavors. Danzig beer, English cider, native African wine, and Mexican pulque are but a few of the aqueous habitats. Ruiz Oronoz (1936) isolated Zygopichia farinosa from the exudate of ash trees in Mexico. In connection with taxonomic work (1944) on the genus Zygosaccharomyces, wherein it was found advisable to transfer certain misplaced film-forming species to Zygopichia, the author became interested in the close relationship between the genera Pichia and Hansenula. Mrak, Phaff, Vaughn, and Hansen (1942) have pointed out that only the ability to utilize nitrate now separates the two genera and they believe it may become necessary to combine the two genera. (Zygopichia and Zygohansenula, along with Zygosaccharomyces, occupy the rank of subspecies in StellingDekker's (1931) system, each being separated from the parent