Overexpression of fumarate reductase results in an increased fermentation rate in yeast

A method for increasing the rate of ethanol production in yeast cells grown on a carbohydrate substrate comprising:

• introducing into parental yeast cells a genetic alteration that causes the modified yeast cells to produce an increased amount of fumarate reductase compared to the parental yeast cells,
• wherein the modified yeast cells have an increased rate of fermentation compared to the rate of fermentation of the parental yeast cells under equivalent fermentation conditions;
• wherein the carbohydrate substrate is substantially free of xylose;
• and
• wherein the fumarate reductase comprises an amino acid sequence having at least 90% sequence identity to the sequence set forth by SEQ ID NO:
• 3 or an amino acid sequence having at least 90% sequence identity to amino acids 33 to 501 of the sequence set forth by SEQ ID NO:3.