Isolation ofyeasts by use ofselective medium. Natural
sources were added into test tubes containing 8 ml of
the selective medium composed of glucose 10%, yeast
extract 0.3 %, citric acid monohydrate 1 % and 2 drops
of Tween 40 per liter.. The cultures were incubated
statically at 30°C for 3 to 5 days. If surface growth
was observed on the culture, the test tubes were shaken
to sink cells growing on surface and then the incubation
was continued. When turbidity was observed in the
test tubes, the culture broth was streaked on agar
medium composed of glucose 10%, yeast extract 0.5 %,
KH2P04 0.1 %, MgS04 •7H20 0.05 %, CaCOs 0.5 % and
agar 2 %. Colonies dissolving CaCOs were isolated
and stocked on potato-dextrose agar