The effects of metal ions on ethanol tolerance of selfflocculating yeast was studied by using a defined medium in shake flask cultureThe observed improvement of zinc ion supplementation on ethanol tolerance promoted the further examination of zinc ion effect on continuous ethanol fermentationZinc sulfate was supplemented into the fermentation medium at the concentrations of 0.01

0.05 and 0.1 g·L-1

respectivelyThe average floc size of the selfflocculating yeast decreased in zincaddition cultures

but both its ethanol tolerance and thermal tolerance were significantly improved

which correlated well with the increased ergosterol and trehalose contents in the yeast flocsIntracellular zinc content was found to be about six folds higher than that of control

and no significant difference was observed in the three addition levelsCorrelation analysis indicated close correlation between zinc addition and ethanol/thermal toleranceEthanol production increased in all the zincsupplemented cultures

with the most significant effect observed when 0.05 g·L-1 zinc sulfate was suppliedThus

zinc ion supplementation was proved to be an efficient strategy for enhanced ethanol tolerance

thermal tolerance and ethanol production in continuous ethanol fermentation of the selfflocculating yeast.