Biotransformation: OnGoing Research

One of the most significant projects we’ve undertaken over the past three years is a partnership with the Shellhammer Lab (Oregon State University, USA) where we explore the biotransformation capacity of selected LalBrew^® Premium brewing yeast strains. These trials, led by principal investigator Ron Samia, have produced a wealth of data that promises to keep us engaged in the topic of biotransformation for the foreseeable future. This deep-dive research aims to achieve two primary goals: first, to better understand how selected yeast strains liberate thiols in hop-forward beers; and second, to establish a research pipeline that will facilitate the evaluation of new yeast strains in the future.

Building on thiol research from oenology 

Research from our colleagues in oenology has shown that specific enzymes play an important role in enhancing tropical and fruity notes in wine, notably D-cysteine desulfhydrase (E.C. 4.4.1.15). This enzyme class is vital for maintaining cysteine balance and facilitating nitrogen scavenging in various organisms, including yeasts and humans. Strains that exhibit a high rate of expression of this enzyme can significantly influence the flavor and sensory perception of various grape cultivars by liberating volatile thiols that contribute to pleasant aromas. 

However, translating insights from oenology directly to brewing is not straightforward. Our project aims to systematically investigate the capacity of selected LalBrew^® Premium strains to liberate aromatic thiols from malt- and hop-derived precursors, a subject that remains largely unexplored. Until recently, particularly since 2018, there were few published studies focused on this topic as it relates to beer sensory characteristics. The existing literature often reflected laboratory conditions that might not accurately represent real-world fermentation processes. Additionally, practical applications of these findings were often shrouded in secrecy or lacked robust scientific backing, leading to misunderstandings among yeast producers and brewers. 

Testing the LalBrew® strains

In our research, we are focusing on several of our flagship yeast strains, including LalBrew Nottingham™, LalBrew Verdant™, LalBrew Diamond™, and LalBrew BRY-97™. We are evaluating how these strains liberate polyfunctional thiols under different nutrient conditions and fermentation temperatures. 

Our findings reveal a strong correlation between both nitrogen content and fermentation temperature in the liberation of key thiols through a mechanism potentially unrelated to the classical D-cysteine desulfhydrase pathway.  Higher free thiol levels were associated with warmer fermentation temperatures and lower nutrient levels (high adjunct, low FAN). There was also variation between each yeast strain, with LalBrew Diamond™ (lager yeast) releasing higher levels of 3SH (tropical, grapefruit, or white wine aromas) than all other strains tested.

These results have some practical implications for brewers looking to enhance thiol release in their beers. However, beer flavor and aroma is very complex with many other compounds playing a role, including esters, terpenes, fatty acids, ketones, and many others. Despite LalBrew Diamond™ showing the highest levels of 3SH in these trials, the trained sensory panel reported higher fruity and tropical aromas for beers fermented with ale yeasts. Thiols only tell one part of the tropical fruit picture, and there are clearly synergistic effects from other flavor compounds that we intend to unravel through our ongoing research.

An ongoing process

As we continue this journey into the particulars of yeast behavior and its impact on beer flavor, we remain committed to sharing our insights and f indings. This small set of lab experiments is not definitive on its own, but rather the first step in the process of translating biological research into practical tools for brewers. This process requires patience, persistence, and collaboration, but the potential benefits for brewers and beer lovers alike are well worth the effort.