Engineering Saccharomyces cerevisiae for increased biotransformation and production of tropical flavors from agricultural products

Company: Berkeley Fermentation Science Inc. (BFS); DBA Berkeley Yeast (BY)Title: Engineering Saccharomyces cerevisiae for increased biotransformation andproduction of tropical flavors from agricultural productsTropical fruit flavors are highly desirable in the fermented beverage market. Thepopularity of these flavors is especially evident in the beer industry where sales ofbeers made with tropical flavoring hops primarily grown in the American PacificNorthwest and Australia/New Zealand has skyrocketed in the last decade. Whiledemand for these beers and the tropical flavoring-hops used to make them hasincreased in recent years extreme weather events like droughts and high winds havesimultaneously threatened and in some cases damaged U.S. flavoring-hop harvests.As increasingly dry and adverse weather events are predicted to become more frequentdue to climate change U.S. hop harvests hop farmers and the production of in- demand beer styles will become increasingly threatened in coming years. While effortsare underway to support the $500M/yr American hop industry through the breeding ofmore resilient and drought tolerant hop cultivars current drought-tolerant plants lack thepungent fruity flavor profiles that brewers and beer drinkers demand.In this SBIR application we propose to develop genetically engineered strains ofbrewers yeast that will produce strong tropical fruit flavors during beer fermentationusing non-aromatic precursor molecules already existing in drought-tolerant hops assubstrates. Specifically we will engineer yeast for production of three volatile thiolmolecules 3MH (guava flavor) 3MHA (passionfruit) and 4MMP (black currant) each ofwhich is a major contributor to the tropical flavor notes of currently popular hopsvarietals. As differing ratios of 3MH 3MHA and 4MMP molecules impart distinctiveflavors in beer we will construct a set of brewing yeast strains in which each strainproduces distinct quantities of these three volatile thiols. This set of strains will providebrewers with an easily scalable toolkit that produces a diversity of tropical fruit flavoredbeers using American-grown non-aromatic drought tolerant hops as substrates.This work will build upon our prior success engineering brewing yeast strains forenhanced 3MH biosynthesis during beer fermentation. In our proposed Phase Iresearch we will develop yeast strains that produce varying ratios of 3MH to 3MHAduring fermentation then test the consumer acceptance and commercial potential ofthis technology. In Phase II work we will develop strains that additionally produce4MMP during fermentation then increase production of all three thiols so as to becomparable to the concentrations achieved through addition of popular flavoring hopvarietals. The end result of Phase II work will be a set of strains that produce distinctmarketable concentrations of 3MH 3MHA and 4MMP during beer fermentation. Thistechnology will provide valuable tools that help the beer and hop industries meetconsumer demand while insulating them from the threat of droughts and severelyreduced hop harvests.1