Preparation of Protein Concentrates and Their Functional Properties from Cells of Alcohol-assimilable Yeast, Hansenula sp.

Abstract

The object of this report is to describe the isolation procedure and functional properties of protein concentrates from ce11s of newly-isolated yeast, Hensenula sp.
Yeast protein concentrate was prepared with a yield of about 60% by ordinary alkali extraction. Yeast cells were incubated at 30°C for 60minutes in 0.05 N NaOH solution, centrifuged and extracted protein was precipitated by the addition of mineral acid to pH 3.4. The yield of protein increased slightly in case of alkali-extracting at higher temperature and it's nucleic acid content reduced to about 1%.
Cellular RNA was preferentialy released from freeze-dried cells with a rate of 90% or more by incubating at 45°C for 60-120 minutes in 0.02M phosphate buffer at pH 7.0. The rate of leakage of RNA was increased by applying "heat shock" at 55°C for 15 seconds during early incubating period. It was found to be necessary to incubate at higher temperature (55°C) in case of fresh yeast cells. The protein concentrate of low nucleic acid content was also obtained by using calcium chloride as a precipitant of protein.
The viscotic behavior to alcohols and viscosity change in alkali solution of the isolated protein were similar to that of soy protein. Water retention (at 4°C or 100°C) and emulsifying capacity of isolated protein were not inferior to soy protein and milk casein and especially it was found that Protein concentrate precipitated by the addition of calcium chloride was superior to casein.