Enhancing Medium Chain Fatty Acid Ethyl Ester Production During Beer Fermentation Through EEB1 and/or ETR1 Overexpression in Saccharomyces pastorianus

Esters are important flavor compounds in alcoholic beverages. Although they are present in trace levels, esters play a key role in flavor formation, especially fruity flavors, in beverages. Low ester contents result in bland beer and unpleasant flavor. In this study, three recombinant strains, ethanol O-acyltransferase-encoding EEB1 overexpression strain (31194::EEB1), 2-enoyl thioester reductase-encoding ETR1 overexpression strain (31194::ETR1), and EEB1/ETR1 co-overexpression strain (31194::EEB1::ETR1), were constructed. Ethyl hexanoate productions by 31194::EEB1 and 31194::EEB1::ETR1 were all 106% higher than that by the parental strain. Further, ethyl octanoate production by 31194::EEB1 and 31194::EEB1::ETR1 were enhanced by 47% and 41%, respectively, compared to that by the parental strain 31194. However, no difference was observed between 31194::ETR1 and the parental strain in terms of ethyl hexanoate and ethyl octanoate production. This indicates that while the EEB1 overexpression in Saccharomyces ...