Extracellular enzyme activity assays
All assays were performed on solid YM medium supplemented
with 2% glucose (unless otherwise specified) and
the appropriate substrate for enzyme activity. The plates
were incubated at the optimal growth temperature of
the individual yeast isolate, and the enzyme activities
determined as described below.
Amylolytic activity. The cells were grown in medium
containing 0.2% soluble starch. The plates were floodedwith 1 ml of iodine solution, and positive activity was
defined as a clear halo around the colony on a purple
background [48].
Cellulase activity. The cells were grown in medium
supplemented with 0.5% carboxymethylcellulose [49].
The plates were flooded with 1 mg/ml of Congo red
solution, which was poured off after 15 min. The plates
were then flooded with 1 M NaCl for 15 min. Positive
cellulase activity was defined as a clear halo around the
colony on a red background [50].
Chitinase activity. The cells were grown in medium
containing 2.5% purified chitin. Chitinase activity was
indicated directly by the presence of a clear halo
around the colony [48].
Lipase activity. The cells were grown in medium
containing 1% tributyrin. Lipase activity was indicated
by a clear halo around the colony [51].
Protease activity. The cells were grown in medium
supplemented with 2% casein at pH 6.5. Protease
activity was indicated by the presence of a white
precipitate around the colony [49].
Xylanase activity. The cells were grown in medium
supplemented with 0.5% xylan [52]. Xylanase activity
was indicated by a clear halo around the colony.
Pectinase activity. The cells were grown in 0.67% YNB
medium, pH 7.0, containing 1% pectin [26]. The plates
were flooded with 1% hexadecyltrimethylammonium
bromide, and activity was indicated by a clear halo
around the colony on a red background [48].
Esterase activity. The cells were grown in medium
composed of 1% bacto peptone, 0.5% NaCl, 0.4%
CaCl2*2H2O and 1% Tween 80 [53], and esterase
activity was indicated by a white precipitate around the
colony.