Screening of thermotolerant yeasts for ethanol
production at high temperature from cassava starch
hydrolysate
Screening for high ethanol fermenting strains was
conducted in duplicate at 40 C in 250- and 500-ml
Erlenmeyer flasks containing 100 and 200 ml of a
cassava starch hydrolysate medium, respectively,
composed of cassava starch hydrolysate adjusted to
16 % glucose, 1 % yeast extract, and 2 % peptone and
with pH adjustment to 5.0. Inoculum was prepared by
transferring one loopful of 18–24 h culture grown on a
slant of YPD agar to a 125-ml Erlenmeyer flask
containing 20 ml cassava starch hydrolysate medium
as above, but composed of only 2 % glucose and
incubated on a rotary shaker at room temperature
(27 ± 3 C) for 18–24 h. The inoculum was transferred
to the screening medium at the same rate which
was used for the screening in YPD broth containing
16 % glucose, followed by incubation on a rotary
shaker at 100 rpm and 40 C.