Physiology, ecology and industrial applications of aroma formation in yeast

Abstract

Yeast cells are often employed in industrial fermentation processes for their ability to efficiently convert relatively high concentrations of sugars into ethanol and carbon dioxide. Additionally, fermenting yeast cells produce a wide range of other compounds, including various higher alcohols, carbonyl compounds, phenolic compounds, fatty acid derivatives and sulfur compounds. Interestingly, many of these secondary metabolites are volatile and have pungent aromas that are often vital for product quality. In this review, we summarize the different biochemical pathways underlying aroma production in yeast as well as the relevance of these compounds for industrial applications and the factors that influence their production during fermentation. Additionally, we discuss the different physiological and ecological roles of aroma-active metabolites, including recent findings that point at their role as signaling molecules and attractants for insect vectors.

Volatiles of bacteria associated with parasitoid habitats elicit distinct olfactory responses in an aphid parasitoid and its hyperparasitoid

“…The bacterial VOC blends comprised typical microbial fermentation products, such as methylated, low molecular weight alcohols and corresponding aldehydes and organic acids (Dzialo et al, ; Schmidt, Cordovez, de Boer, Raaijmakers, & Garbeva, ). However, some compounds like geraniol, linalool, limonene, 2‐phenylethanol, phenylacetaldehyde and acetophenone are also commonly reported as typical plant volatiles (Bruce & Pickett, ; Dudareva, Klempien, Muhlemann, & Kaplan, ).…”

“…Specifically, data were combined for strains evoking parasitoid attraction, repellence or a neutral response. Chemical classes generally induce similar responses in insects (Dzialo et al, ). However, caution should be taken when interpreting results as this is not always the case, for example, for terpenes (Raffa, ).…”

“…Bioassays using the vinegar fly Drosophila melanogaster to assess odours of nine phylogenetically and ecologically distinct yeast species revealed that the flies were attracted to all yeast species studied (Becher et al, ). So far, only very little is known whether these results are also representative for bacteria, which often produce different mVOCs or use other biochemical synthesis pathways than yeasts (Dzialo et al, ; Schulz & Dickschat, ). However, there is already some evidence that insects are attracted to bacteria that live on or near hosts or preys (Leroy, Sabri, Heuskin, et al, ; Leroy, Sabri, Verheggen, et al, ; Mazzetto et al, ) and that the mVOCs produced by these bacteria can be exploited by natural enemies to locate their hosts or preys (Boone, Six, Zheng, & Raffa, ; Dillon, Vennard, & Charnley, ; Leroy, Sabri, Heuskin, et al, ).…”

“…Volatiles from both aerial and underground plant parts play an important role in the communication between plants and insects (Meiners, ; Soler, Bezemer, & Harvey, ), while insect‐derived volatiles have been intensively studied to better understand critical processes in insects such as mating, reproduction, aggregation and alarming conspecifics about danger (Wyatt, ). More recently, increasing evidence indicates that micro‐organisms like bacteria and fungi also emit volatile compounds that affect insect behaviour (Davis, Crippen, Hofstetter, & Tomberlin, ; Dzialo, Park, Steensels, Lievens, & Verstrepen, ; Leroy, Sabri, Verheggen, et al, ). Although production of microbial volatile organic compounds (mVOCs) is commonplace (Piechulla & Degenhardt, ), little is still known about their ecological role and how they interfere with volatile‐mediated insect foraging behaviour.…”

The Smell of Synthetic Biology: Engineering Strategies for Aroma Compound Production in Yeast

“…This paper is distinct from other published reviews, including those that extensively covered the use of flavour-active brewing and wine yeasts for the enhancement of the aroma of beer and wine [9,10,11]. Here, we focus on the exploitation of two types of yeast precursors which are responsible for a variety of aroma compounds, namely the aromatic amino acids L-tyrosine and L-phenylalanine, which are derived from the shikimate pathway, and the mevalonate pathway-derived isoprenoid precursors dimethylallyl pyrophosphate and isopentenyl pyrophosphate.…”