The concentrations of the fermentation products obtained with the different CAT2 overexpression strains indicate that the expression levels of the CAT2 gene have an effect on ester production. For some esters such as ethyl acetate and isoamyl acetate, overexpression of mitochondrial Cat2p caused a significant reduction in their concentrations com- pared with control cells. At the same time, overexpression of mitochondrial Cat2p caused a 50% increase in the levels of
2-methyl propanol. A precursor for propanol is a-keto butyrate, which is also a precursor for ethyl butanoate.