Biology subjects

Visinoni, F.

Publications and source records attributed to Visinoni, F..

5 recordsLinked to original sources

bioRxiv2024

Aroma compounds profile is affected by the initial yeast ratio in wort co-fermentations

In recent years, the boom of the craft beer industry refocused the biotech interest from ethanol production to diversification of beer aroma profiles. This study analyses the fermentative phenotype of a collection of non-conventional yeasts and examines their role in creating new flavours, particularly through co-fermentation with industrial Saccharomyces cerevisiae. High-throughput solid and liquid media fitness screening compared the ability of eight Saccharomyces and four non-Saccharomyces yeast strains to grow in wort. We determined the volatile profile of these yeast strains and found that Hanseniaspora vineae displayed a particularly high production of the desirable aroma compounds ethyl acetate and 2-phenethyl acetate. Given that H. vineae on its own was a poor fermenter, we carried out mixed wort co-fermentations with a S. cerevisiae brewing strain at different ratios. The two yeast strains were able to co-exist throughout the experiment, regardless of their initial inoculum, and the increase in the production of the esters observed in the H. vineae monoculture was maintained, alongside with a high ethanol production. Moreover, different inoculum ratios yielded different aroma profiles: the 50/50 S. cerevisiae/H. vineae ratio produced a more balanced profile, while the 10/90 ratio generated stronger floral aromas. Our findings show the potential of using different yeasts and different inoculum combinations to tailor the final aroma, thus offering new possibilities for a broader range of beer flavours and styles. IMPORTANCECraft brewing underwent an unprecedented growth in the last years due to customer demand for more unique and complex beverages. Brewers started to explore innovative fermentation methods using new ingredients, different brewing conditions, and new yeasts to explore a larger flavour landscape. The use of non-Saccharomyces yeasts has emerged as an effective strategy to produce novel distinct flavour profiles, however, knowledge regarding their fermentation performance and volatiles production is still limited, which hinders their industrial application. In this study, we expand on the knowledge of several non-Saccharomyces yeasts in terms of their brewing application and highlight the potential of H. vineae in co-fermentation with S. cerevisiae for producing unique fruity beers with a standard ethanol content. Our findings provide the craft beer industry with a new strategy to produce distinctive fruity beers.

microbiology↗

bioRxiv2024

Impact of inter-species hybridisation on antifungal drug response in the Saccharomyces genus.

Antifungal drug resistance across fungal and yeast pathogens presents one of the major concerns for global public health. Understanding the interactions between genetic background and environment is important for the development of new, effective treatments of infections. Allelic variation within populations of Ascomycota as well as hybridisation impacts the phenotype in response to stressful conditions, including to antifungal drugs. We exploited recent advances in multigenerational breeding of Saccharomyces interspecies hybrids to study the impact of hybridisation on antifungal resistance and identify quantitative trait loci (QTL) responsible for the phenotypes observed. A library of Saccharomyces cerevisiae x S. kudriavzevii hybrid offspring was screened in the presence of sub-lethal concentrations of six antifungal drugs and revealed a broad phenotypic diversity across the progeny. QTL analysis was carried out comparing alleles between the pools of high and low fitness offspring, identifying hybrid-specific genetic regions involved in resistance to fluconazole, micafungin and flucytosine. We found both drug specific and pleiotropic regions, and through gene ontology and SIFT analysis we identify potential causal genes, such as BCK2 and DNF1 that were validated via reciprocal hemizygosity analysis. We highlight 41 regions that contain genes not previously associated with resistance phenotypes in the literature. The results of this screening will help identify new pathways contributing to drug resistance, and lead to greater understanding of how allelic variation, hybridisation and evolution affect antifungal drug resistance in yeast and fungi.

genetics↗

bioRxiv2022

Volatile aroma compound production is affected by growth rate in S. cerevisiae

The initial growth rate of a yeast strain is a key parameter in the production of fermented beverages. Fast growth is linked with higher fermentative capacity and results in less slow and stuck fermentations unable to reach the expected final gravity. As concentrations of metabolites are in constant state of flux, quantitative data on how growth rate affects the production of aromatic compounds becomes an important factor for brewers. Chemostats allow to set and keep a specific dilution rate throughout the fermentation and are ideal system to study the effect of growth on aroma production. In this study, we run chemostats alongside batch and fed-batch cultures, compared volatile profiles detected at different growth rates, and identified those affected by the different feeding profiles. Specifically, we quantified six abundant aroma compounds produced in anaerobic glucose-limited continuous cultivations of S. cerevisiae at different dilution rates. We found that volatile production was affected by the growth rate in four out of six compounds assayed, with higher alcohols and esters following opposite trends. Batch and fed-batch fermentations were devised to study the extent by which the final concentration of volatile compounds is influenced by glucose availability. When compared to the batch system, fed-batch fermentations, where the yeast growth was artificially limited by a slow constant release of nutrients in the media, resulted in a significant increase in concentration of higher alcohols, mirroring the results obtained in continuous fermentations. This study paves the way to further process development optimization for the production of fermented beverages. ImportanceThe production of fermentation beverages will need to quickly adapt to changes in both the climate and in customer demands, requiring the development of new strains and processes. Breakthroughs in the field are hindered by the limited knowledge on the physiological role of aroma compounds production in yeast. No quantitative data on how growth rate affects aroma profile is available in the literature to guide optimisation of the complex flavours in fermented beverages. In this study, we exploited the chemostat system, alongside with batch and fed-batch cultures to compare volatile profiles at different growth rates. We identified the aromatic compounds affected by the different feeding profiles and nutrient limitations. Moreover, we uncovered the correlation between yeast growth, esters and higher alcohols production. This study showcases the potential of the application of feeding profiles for the manipulation of aroma in the craft beverage industry.

microbiology↗

bioRxiv2021

Restoring fertility in yeast hybrids: breeding and quantitative genetics of beneficial traits

Hybrids species can harbour a combination of beneficial traits from each parent and may exhibit hybrid vigour, more readily adapting to new harsher environments. Inter-species hybrids are also sterile and therefore an evolutionary dead-end unless fertility is restored, usually via auto-polyploidisation events. In the Saccharomyces genus, hybrids are readily found in nature and in industrial settings, where they have adapted to severe fermentative conditions. Due to their hybrid sterility, the development of new commercial yeast strains has so far been primarily conducted via selection methods rather than breeding. In this study, we overcame infertility by creating tetraploid intermediates of Saccharomyces inter-species hybrids, to allow continuous multigenerational breeding. We incorporated nuclear and mitochondrial genetic diversity within each parental species, allowing for quantitative genetic analysis of traits exhibited by the hybrids, and for nuclear-mitochondrial interactions to be assessed. Using pooled F12 generation segregants of different hybrids with extreme phenotype distributions, we identified QTLs for tolerance to high and low temperatures, high sugar concentration, high ethanol concentration, and acetic acid levels. We identified QTLs that are species specific, that are shared between species, as well as hybrid specific, where the variants do not exhibit phenotypic differences in the original parental species. Moreover, we could distinguish between mitochondria-type dependent and independent traits. This study tackles the complexity of the genetic interactions and traits in hybrid species, bringing hybrids into the realm of full genetic analysis of diploid species, and paves the road for the biotechnological exploitation of yeast biodiversity.

genetics↗

bioRxiv2021

Biotechnological exploitation of Saccharomyces jurei and its hybrids in craft beer fermentation uncovers new aroma combinations.

Hybridization is an important evolutionary mechanism to bring about novel phenotypes and may produce new hybrids with advantageous combinations of traits of industrial importance. Within the Saccharomyces group, Saccharomyces jurei is a newly discovered species and its biotechnological potential has not yet been fully explored. This yeast was found to be able to grow well in synthetic wort and at low temperatures, qualities necessary in good candidates for fermentated bevarages. Here, we analysed its fermentation and aroma profile and created novel non-GMO hybrids between S. jurei and S. cerevisiae ale yeasts to develop new starter strains with interesting flavours for the craft beer industry. Pilot beer fermentations with specific hybrids showed a good fermentation performance, similar to the ale parent strain, while presenting a better sugar attenuation and a more complex flavour profile. This study exploits the genetic diversity of yeasts and show how inter-specific hybridisation and clone selection can be effectively used in brewing to create new products and to eliminate or increase specific traits.

microbiology↗