The S. cerevisiae Z1–15 are all diploid strains. Z1–3 were isolated
from a soil sample, Z4–9 were received from Henan Tianguan
Fuel Ethanol Co. Ltd., and Z10–12 were isolated from Angel active
dry yeasts. The genetic background of Z13–15 (stored by our laboratory)
was S. cerevisiae var. ellipsoideus. The growth medium
(YPD) contained: 1% yeast extract, 2% peptone, 2% glucose (w/v),
and had a pH of 5.5. The fermentation medium was prepared from
corn meal via the double enzyme hydrolyzed method (Graves et al.,
2007).