The highest protein levels (51.1–53.8% DM) were observed in
the C. tropicalis biomass. The lowest protein content
(42.3(±4.2)% DM) was found in T. cutaneum cells obtained with
diammonium phosphate as the sole nitrogen additive to the hydrolysate.
The highest differences in crude protein content were
observed for the T. cutaneum biomass – 42.3(±4.2)% DM for supplementation
with ammonium ions, to 51.3(±2.16)% DM for biomass
obtained with a mixture of ammonium ions and urea added to
the medium. High crude protein results for biomass of strains
which were not able to assimilate urea, i.e. C. tropicalis and C. guilliermondii,
may be explained by the significantly low biomass yield
and the accumulation of supplemented nitrogen in the biomass,
even if it was not incorporated into the proteins. The protein concentration
depends on the specific cultivation conditions and on
medium content, therefore it is difficult to compare the data we
obtained with that in suitable literature. The crude protein content
in fodder yeast biomass as reported by others usually varied from40% to 60% of DM. Ezekiel et al. (2012) reported a protein concentration
in the range of 49.1–56.7% DM in the biomass of C. utilis
obtained with the use of cassava peel acid and enzymatic hydrolysate
as a medium. Tauk (1982) reported a wide range of protein
content in C. guilliermondii and C. tropicalis biomass (20.1-51.6%
DM), depending on the medium content and cultivation
conditions.