High ergosterol-producing yeast strains YEH-28 and YEH-56 were constructed
by hybridization of two haploids with opposite mating types from different
species. The fermentation conditions of hybrid strain YEH-56 were studied.
The highest level of ergosterol was obtained in 30 h at 28 degrees C and 20
0 rpm, when 60 ml of culture in 250-ml shake flasks was grown in fermentati
on medium that consisted of (per liter): 100 g glucose; 10 g peptone and 10
g yeast extract. The initial pH was adjusted to 6.0, The optimal inoculum
volume was 10% (v/v). Under optimal conditions, the yield of ergosterol of
YEH-28 strain is 1.96 and 1.56 times that of the parental strains YE39 and
YE244, whereas that of YEH-56 is 1.98 and 1.57 times that of the parental s
trains YE39 and YE244, respectively. Analysis of genetic stability showed t
hat hybrid strains YEH-28 and YEH-56 are stable genetically.