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Saccharomyces cerevisiae can undergo filamentous growth in response to specific environmental stressors, particularly nitrogen-limitation, whereby cells undergo pseudohyphal differentiation, a process where cells transition from a singular ellipsoidal appearance to multicellular filamentous chains from the incomplete scission of the mother-daughter cells. Previously, it was demonstrated that filamentous growth in S. cerevisiae is co-regulated by multiple signaling networks, including the glucose-sensing RAS/cAMP-PKA and SNF pathways, the nutrient-sensing TOR pathway, the filamentous growth MAPK pathway, and the Rim101 pathway, and can be induced by quorum-sensing aromatic alcohols, such as 2-phenylethanol. However, the prevalent research on the yeast-pseudohyphal transition and its induction by aromatic alcohols in S. cerevisiae has been primarily limited to the strain Σ1278b. Due to the prospective influence of quorum sensing on commercial fermentation, the native variation of yeast-to-filamentous phenotypic transition and its induction by 2-phenylethanol in commercial brewing strains was investigated. Image analysis software was exploited to enumerate the magnitude of whole colony filamentation in 16 commercial strains cultured on nitrogen-limiting SLAD medium; some supplemented with exogenous 2-phenylethanol. The results demonstrate that phenotypic switching is a generalized, highly varied response occurring only in select brewing strains. Nevertheless, strains exhibiting switching behavior altered their filamentation response to exogenous concentrations of 2-phenylethanol.

In contrast to other fermented beverages, beer quality generally diminishes over time. This diminishing quality hinges heavily on the oxidative degradation of beer compounds by reactive oxygen species (ROS), whose formation is in part catalyzed by Fe(II) ions via the Fenton and Haber-Weiss reactions. Consequently, ROS accumulation throughout the brewing process results in oxidative instability and accelerates numerous beer staling reactions, like those frequently associated with the onset of unwanted flavors, aromas, and an unaesthetic appearance. However, despite its critical importance to beer stability, the oxidative state of iron in wort and finished beer continues to be poorly characterized. In this investigation, the influence of kilned specialty malt utilization on total free iron and iron ion speciation in wort was determined by EBC Method 9.13.1. Further, the reducing power of each wort was determined via 2,2-diphenyl-1-picrylhydrazyl (DPPH). Here, we demonstrate that kilned specialty malt utilization influences total iron concentration, the balance between Fe(II) and Fe(III) ion species, and the reducing power of wort. Furthermore, our results reveal a negative correlation between mash pH and total iron concentration in finished wort. These results indicate that beer’s oxidative flavor stability may be improved by using lower kilned malts and adjusting mash pH.

Much like other living organisms, yeast cells have a limited life span, in terms of both the maximal length of time a cell can stay alive (chronological life span) and the maximal number of cell divisions it can undergo (replicative life span). Over the past years, intensive research revealed that the life span of yeast depends on both the genetic background of the cells and environmental factors. Specifically, the presence of stress factors, reactive oxygen species, and the availability of nutrients profoundly impact life span, and signaling cascades involved in the response to these factors, including the target of rapamycin (TOR) and cyclic adenosine monophosphate (cAMP)/protein kinase A (PKA) pathways, play a central role. Interestingly, yeast life span also has direct implications for its use in industrial processes. In beer brewing, for example, the inoculation of finished beer with live yeast cells, a process called “bottle conditioning” helps improve the product's shelf life by clearing undesirable carbonyl compounds such as furfural and 2‐methylpropanal that cause staling. However, this effect depends on the reductive metabolism of living cells and is thus inherently limited by the cells' chronological life span. Here, we review the mechanisms underlying chronological life span in yeast. We also discuss how this insight connects to industrial observations and ultimately opens new routes towards superior industrial yeasts that can help improve a product's shelf life and thus contribute to a more sustainable industry., This review article outlines the mechanisms underlying chronological life span in yeast, with a focus on nutrient signaling pathways and strain‐to‐strain differences in chronological life span. It also connects these insights to industrial observations, which opens new routes towards the generation of superior industrial yeasts.

Inter- and intraspecies communication between microorganisms is recognized to play an influential role across many relevant applications, such as bioethanol production, food preservation, bioremedi...

Kombucha tea is made by aerobically fermenting a sweetened tea infusion with a kombucha culture, a symbiotic culture of bacteria and yeasts. The resulting beverage is usually non-alcoholic, sour an...

The aerial portion of plants (phyllosphere) harbors complex and diverse microbial communities that have been shown to influence host growth and fitness, tolerance to environmental stressors, diseas...