Ploidy influences the functional attributes of de novo lager yeast hybrids

Abstract

The genomes of hybrid organisms, such as lager yeast (Saccharomyces cerevisiae × Saccharomyces eubayanus), contain orthologous genes, the functionality and effect of which may differ depending on their origin and copy number. How the parental subgenomes in lager yeast contribute to important phenotypic traits such as fermentation performance, aroma production, and stress tolerance remains poorly understood. Here, three de novo lager yeast hybrids with different ploidy levels (allodiploid, allotriploid, and allotetraploid) were generated through hybridization techniques without genetic modification. The hybrids were characterized in fermentations of both high gravity wort (15 °P) and very high gravity wort (25 °P), which were monitored for aroma compound and sugar concentrations. The hybrid strains with higher DNA content performed better during fermentation and produced higher concentrations of flavor-active esters in both worts. The hybrid strains also outperformed both the parent strains. Genome sequencing revealed that several genes related to the formation of flavor-active esters (ATF1, ATF2¸ EHT1, EEB1, and BAT1) were present in higher copy numbers in the higher ploidy hybrid strains. A direct relationship between gene copy number and transcript level was also observed. The measured ester concentrations and transcript levels also suggest that the functionality of the S. cerevisiae- and S. eubayanus-derived gene products differs. The results contribute to our understanding of the complex molecular mechanisms that determine phenotypes in lager yeast hybrids and are expected to facilitate targeted strain development through interspecific hybridization.Electronic supplementary materialThe online version of this article (doi:10.1007/s00253-016-7588-3) contains supplementary material, which is available to authorized users.

New Lager Brewery Strains Obtained by Crossing Techniques Using Cachaça (Brazilian Spirit) Yeasts

“…In contrast, triploid and tetraploid hybrids obtained by crossing between S. cerevisiae and S. eubayanus showed a much higher flocculation ability than the corresponding segregant diploid hybrids (35). Some phenotypic traits were also affected by the ploidy level in other interspecific Saccharomyces hybrids, where triploid and tetraploid hybrids were able to produce more ethanol and 3-methylbutyl acetate than their parental strains and diploid hybrids (7).…”

Diacetyl control during brewery fermentation via adaptive laboratory engineering of the lager yeast Saccharomyces pastorianus

“…Pair-end reads from the NextSeq 500 sequencing were quality analysed with FastQC [3], and trimmed and filtered with Skewer [25]. Reads were aligned to a concatenated reference sequence of S. cerevisiae A62 [29] and S. eubayanus FM1318 [4] using BWA-MEM [33]. Alignments were filtered to a minimum MAPQ of 50 with SAMtools [32] and the quality of alignments was assessed with QualiMap [16].…”

Mating of 2 Laboratory <b><i>Saccharomyces cerevisiae</i></b> Strains Resulted in Enhanced Production of 2-Phenylethanol by Biotransformation of <smlcap>L</smlcap>-Phenylalanine

“…This might be due to a higher physiological activity, since it is commonly known that the diploid or polyploid yeast strains used in industrial bioprocesses express an increased metabolic activity when compared to haploids [Benitez et al, 1996;Krogerus et al, 2016] and enhanced resistance to the toxic 2-PE accumulation in broth. The AM1-d strain grows better than parental strains in media dedicated for L -Phe bioconversion to 2-PE, thus it might be the reason for increased 2-PE production.…”

“…Thus, the diploid AM1-d strain displays a stronger resistance to the exogenous 2-PE which, combined with the better growth, might be the main reason of the enhanced 2-PE production by AM1-d. Besides, other potential reasons for this heterotic phenotype cannot be excluded, such as an en- hanced activity of enzymes in the Ehrlich pathway, since L -Phe is converted to 2-PE through this pathway [Krogerus et al, 2016;Yamada et al, 2010]. In further studies, it would also be interesting to compare several different diploid hybrids constructed from different parent strains, in order to see how common this heterotic phenotype is with regard to 2-PE synthesis.…”

“…However, because of complicated legislation and negative consumer attitude to genetically modified organisms (GMO), non-GMO strategies are highly recommended and have previously been successfully applied to industrial yeast strains, including the improvement of ethanol tolerance [Stanley et al, 2010], copper resistance [Adamo et al, 2012], or aroma production [Steensels et al, 2014]. Recent studies have also shown that hybrid strains often exhibit a heterotic phenotype in regard to compounds in the Ehrlich pathway [Krogerus et al, 2015[Krogerus et al, , 2016. Hence, it is likely that enhanced 2-PE production can also be achieved through hybridization.…”