Fig. 1
From: Industrial brewing yeast engineered for the production of primary flavor determinants in hopped beer
Engineering brewer’s yeast to express monoterpene biosynthetic pathways thereby replacing flavor hop addition. a During the brewing process, S. cerevisiae converts wort—a barley extract solution rich in fermentable sugars—into ethanol and other by-products. Hops are added immediately before, during, or after fermentation to impart “hoppy” flavor. Engineered strains produce linalool and geraniol, primary flavor components of hoppy beer, thereby replacing hop additions. b Six full-length plant-derived linalool synthase genes, as well as PTS-truncated variants, were expressed on high-copy plasmids. Full-length genes and PTS-truncated genes predicted by either ChloroP (C) or the RR-heuristic method (RR) are indicated by colored lines. c Error bars correspond to mean ± standard deviation of three biological replicates. Asterisks indicate statistically significant increases in monoterpene production compared with the control strain (Y) as determined by a t-test using p-value <0.025. The LIS from the California wildflower Clarkia breweri has been shown to increase production of linalool when heterologously expressed in plants47 and in yeast48. However, when C. breweri LIS was expressed, either with native codons (nCb) or “yeast-optimized” codons (Cb), linalool was not detected. The Mentha citrata LIS (Mc) truncated at the RR motif was identified as sufficiently active to allow for monoterpene production at levels characteristic of commercial beer and was chosen for integration into brewer’s yeast strains
