The lager brewing yeasts, Saccharomyces pastorianus (synonym Saccharomyces carlsbergensis), are allopolyploid, containing parts of two divergent genomes. Saccharomyces cerevisiae contributed to the formation of these hybrids, although the identity of the other species is still unclear. The presence of alleles specific to S. cerevisiae and S. pastorianus was tested for by PCR/RFLP in brewing yeasts of various origins and in members of the Saccharomyces sensu stricto complex. S. cerevisiae-type alleles of two genes, HIS4 and YCL008c, were identified in another brewing yeast, S. pastorianus CBS 1503 (Saccharomyces monacensis), thought to be the source of the other contributor to the lager hybrid. This is consistent with the hybridization of S. cerevisiae subtelomeric sequences X and Y' to the electrophoretic karyotype of this strain. S. pastorianus CBS 1503 (S. monacensis) is therefore probably not an ancestor of S. pastorianus, but a related hybrid. Saccharomyces bayanus, also thought to be one of the contributors to the lager yeast hybrid, is a heterogeneous taxon containing at least two subgroups, one close to the type strain, CBS 380 T , the other close to CBS 395 (Saccharomyces uvarum). The partial sequences of several genes (HIS4, MET10, URA3) were shown to be identical or very similar (over 99 %) in S. pastorianus CBS 1513 (S. carlsbergensis), S. bayanus CBS 380 T and its close derivatives, showing that S. pastorianus and S. bayanus have a common ancestor. A distinction between two subgroups within S. bayanus was made on the basis of sequence analysis : the subgroup represented by S. bayanus CBS 395 (S. uvarum) has 6-8 % sequence divergence within the genes HIS4, MET10 and MET2 from S. bayanus CBS 380 T , indicating that the two S. bayanus subgroups diverged recently. The detection of specific alleles by PCR/RFLP and hybridization with S. cerevisiae subtelomeric sequences X and Y' to electrophoretic karyotypes of brewing yeasts and related species confirmed our findings and revealed substantial heterogeneity in the genome constitution of Czech brewing yeasts used in production.

The anti-proliferative activity of hesperetin, hesperidin, neohesperidin and rutin was evaluated on human hepatoma cell lines (Hep G2) and correlated to their antioxidant activity. The results obtained showed strong anti-proliferative effects of hesperidin and neohesperidin, considerably higher than the other two additives. Hesperetin induced caspase-3 activation, release of LDH and endogenous accumulation of putrescine. Cell cycle distribution seems to indicate that the inhibitory effects of polyphenols on cell growth could be due to G0/G1 block, and activation of apoptotic pathway in the presence of hesperetin. Our results underline also that the glycone forms show reduced scavenging activity against DPPH, but present a remarkable inhibition of cell proliferation and low cytotoxicity.

No abstract

No abstract