![]() ![]() Using CRISPR/Cas9, we were able to insert patB into a classic Chico (West Coast Ale I) strain and found that the results were even more intense than just the activated IRC7 gene! The resulting strain is Star Party, which generates a massive thiol burst while maintaining the fermentation character of its famous parent strain. The bacterial PatB acts very similar to the yeast β – lyase Irc7 - it cleaves cysteine-thiol precursors found in malt and hops to let those thiols shine - but PatB is more active and more specific. hominis generated the greatest amount of passion fruit and guava compounds. hominis, which commonly occurs on human skin as part of our natural microbiome that protects us from pathogens. ![]() Our research pointed us to a β – lyase called PatB, specifically that of S. The success of the Cosmic Punch tests led the team to look into other sources of β – lyases to see if we could boost thiol output even further. Using CRISPR/Cas9, we were able to add this activated IRC7 into British V, creating our first Thiolized strain: Cosmic Punch. ![]() We tried combining this IRC7 gene with the highly active promoter from the other trials and found that it worked like a charm. We continued digging and discovered that the IRC7 gene in our Chico ( West Coast Ale I) was functional, though it was not expressed in wort. Unfortunately, British V has mutations that inactivate its IRC7 gene, meaning there was no chance for it to work, regardless of how much enzyme was made in that strain.īack to the drawing board. We replaced its inactive IRC7 promoter with a highly active one, but found that the levels of 3SH remained unchanged in comparison to the non-modified British V. We began experimenting with our British V, a popular strain many brewers use for making classic hazy IPAs. By finding a way to keep the IRC7 gene functional, we should theoretically be able to unlock thiol precursors and derive more flavor and aroma from our malt and hops. We explored the possibility of altering the IRC7 promoter (the sequence that controls the gene’s expression) to a version that would keep the gene active at all times, even in a high-nitrogen environment. The problem, however, is that many brewing strains have mutations in the IRC7 gene that disable the enzyme, and those strains that do have a functional IRC7 gene don’t make the enzyme in wort because high nitrogen levels (like we see in wort) turn off the gene. We dug into the literature and focused on IRC7, a gene in yeast that encodes an enzyme (β – lyase) that frees thiols from their precursor form. Our R&D team became curious about thiols and methods for making the process of freeing thiols more efficient. In beer and wort, the overwhelming majority of these thiol compounds are in precursor form (1000-fold!) and are a stockpile of aroma potential with a yeast capable of biotransforming them to the free volatile and aromatic thiol compounds. The precursor for 3‑sulfanyl-1-hexanol (3SH, but also referred to as 3MH - a thiol known for its intense grapefruit and passion fruit aromas) is abundant in barley, but does not reach sensory thresholds until converted to its free form. New World hop varietals, specifically Southern Hemisphere hops, appear to be the highest in free thiols, which contribute to their characteristic tropical fruit aromas. Hop varieties vary widely, not only in the amount of thiol compounds, but also the percentage that are in the non-volatile precursor form. The precursor forms, abundant in malt, are non-aromatic and require yeast with β – lyase biotransformation activity to release them. These thiol compounds exist in two forms - free forms, which are highly aromatic and volatile, and precursor forms (i.e., glutathione- and cysteine-bound thiols). Volatile thiols are highly impactful aroma compounds that evoke grapefruit, passion fruit, and guava and are found in a variety of tropical fruits, wine grapes, and hops. What are thiols and where do they come from? As it turns out, typical yeast biotransformation of thiol precursors is very inefficient in wort, but by employing these Thiolized strains in fermentation, brewers can expect a significant increase in thiol output. The Thiolized series is focused on the second category, working to give brewers access to the biotransformation of thiol precursors.
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