Biology subjects

Lopandic, K.

Publications and source records attributed to Lopandic, K..

3 recordsLinked to original sources

bioRxiv2025

Commercial Saccharomyces cerevisiae baker's yeasts: strain redundancy, genome plasticity, and colonization of the sourdough environment and the human body

Leavening dough is one of the most widespread applications of fermentative yeast and the most common practice for the general public to come into contact with microbial cultures. Saccharomyces cerevisiae is the typical species used for dough making, but the evolutionary origin of strains isolated from dough is mixed. Here, using 49 newly sequenced and 183 previously described isolates from the bakery environment, we show that the traditional strains used in Europe for sourdough making are more closely related to Chinese Mantou sourdough lineages than to commercially used baker yeast strains. Surprisingly, the expansion of these traditional European strains into other human-associated niches, including the human body, has been very limited. This is in stark contrast to the Mixed-origin clade commercial baking yeasts, which consists of only a few globally distributed clonal lineages that dominate the yeast market and recurrently colonize sourdoughs and human hosts. These clonal lineages consistently maintain their ploidy, unique heterozygous chromosomal rearrangements, and stable aneuploidies in addition to several diverse structural variants. In addition to the previously known diploid and tetraploid groups of commercial isolates, we describe a widely distributed stable triploid aneuploid clonal lineage. We show that company practices and global trade help the distribution of these clonal clusters and that these yeasts are characterized by their exclusively mitotic reproduction.

microbiology↗

bioRxiv2018

Fermentation characteristics of mead and wine generated by yeasts isolated from beehives of two Austrian regions

Mead is a traditional alcoholic beverage that is produced by fermentation of diluted honey. The mead quality is primarily influenced by the honey variety, although the yeast microflora as the main catalyst of alcoholic fermentation also plays a significant role in the organoleptic and chemical quality of the final product. The impact of the indigenous honey associated-yeasts on the mead properties has scarcely been investigated. To fill this gap the main objective of this work was to assess the metabolic properties of the yeasts isolated from honey and pollen from beehives of northeast Austria.\n\nThe biodiversity was low and only two yeast species were identified, Zygosaccharomyces rouxii and Candida apicola. The fermentation potentials of these yeasts were estimated in two media, grape juice (since yeasts isolated from honey may be useful for sweet wine production) and diluted honey of similar sugar concentration, and compared with those of the reference strains Saccharomyces cerevisiae; S. uvarum and S. eubayanus. Depending on the fermentation substrate, yeasts differed with respect to their metabolic power, fermentation rate, sugar utilization and production of glycerol and organic acids. During mead fermentation Saccharomyces species showed the highest metabolic turnover, while the fermentation rate did not differ significantly. Addition of assimilable nitrogen to the diluted honey enhanced fermentation rate of S. cerevisiae, but not of the other species. Fermentation of grape juice occurred much faster than that of diluted honey and differences between yeasts were more pronounced. The S. cerevisiae commercial wine strain, adapted to high alcohol concentrations, and S. eubayanus outperformed the others, S. uvarum was comparable with Z. rouxii, while C. apicola had the lowest fermentation rate. Fructophily of Z. rouxii and to a lesser degree of C. apicola was observed in both media. An increased production of glycerol was achieved by S. eubayanus in both media and by C. apicola during the fermentation of honey must. A commercial S. cerevisiae strain, S. eubayanus and Z. rouxii were able to metabolize malic acid in wine. In mead, the S. eubayanus and S. uvarum yeasts showed the tendency of increasing the level of malic acid. Aroma profile depended profoundly on yeast species. This study demonstrates that the composition and complexity of the fermentation substrate determines the activity and the final metabolic outcomes of the studied yeasts.

microbiology↗

bioRxiv2018

Seasonal variation of fermentation rate in Saccharomyces spp. (Ascomycota)?

Yeast species of the genus Saccharomyces show some reaction to visible light - although they lack photo pigments and the typical clock genes of fungi - that can be explained by damage of the cytochrome electron transport chain of the mitochondria. Evidence for a circadian clock, entrainable by cyclic environmental stimuli, exists for periodic changing temperature and light as zeitgeber. Whether seasonality follows from the existence of a circadian clock - which is a necessary requirement for annual rhythms - remains unknown.\n\nDue to an accidental observation, we were able to show that fermentation taking place in complete darkness and at constant temperature is influenced in some yeast strains by the history of the inoculum culture. Using yeast cultures growing on agar plates and exposed to diffuse daylight for three weeks either in March or in May as inoculum, leads to significantly different fermentation rates in the inoculated grape juice in both months: rates are higher in March when day length is shorter than in May. In must inoculated with cultures that grew in darkness or daylight, respectively, higher fermentation rates occur by the former. Other yeast strains react to artificial white light in the same way.\n\nWe used strains of S. cerevisiae, S. eubayanus, S. kudriavzevii, S. uvarum and furthermore hybrid strains of two or even three of these species. The most pronounced reaction to daylight was shown by the S. eubayanus x S. uvarum x S. cerevisiae hybrid, followed by S. cerevisiae x S. kudriavzevii hybrids, S. eubayanus and S. cerevisiae. S. uvarum was sensitive to artificial white light.\n\nThese observations can hardly be explained by some kind of photo damage because they base on an effect that persists through many cell division cycles after yeasts were exposed to light. If it really represents seasonality epigenetic memory is likely involved, since fermentation lasts for many days and yeast generations. If the existence of a circadian clock and seasonal behaviour in Saccharomyces is confirmed these yeasts could become an important tool in basic research concerning epigenetic memory.

microbiology↗