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Saccharomyces pastorianus



Saccharomyces pastorianus
Scientific classification
Kingdom: Fungi
Phylum: Ascomycota
Subphylum: Saccharomycotina
Class: Saccharomycetes
Order: Saccharomycetales
Family: Saccharomycetaceae
Genus: Saccharomyces
Species: S. pastorianus
Binomial name
Saccharomyces pastorianus
Nguyen & Gaillardin ex. Beijerinck
Synonyms

Saccharomyces carlsbergensis

Saccharomyces pastorianus is a yeast, used industrially for the production of lager beer. It is a synonym of the yeast species Saccharomyces carlsbergensis[1], which was originally described in 1883 by Emil Christian Hansen, who was working for the Danish brewery Carlsberg.

Additional recommended knowledge

Contents

Genomics

As S. pastorianus is a hybrid of Saccharomyces bayanus and Saccharomyces cerevisiae it is not surprising that there is a degree of phenotypic and genomic similarity between the two species.[2] The hybrid nature of S. pastorianus also explains the genome size, which is up to 60% larger than that of S. cerevisiae as it includes large parts of the two genomes[3]. However there is growing evidence that S. pastorianus has inherited most of its genetic material from S. bayanus[3]. Indeed the mitochondrial DNA[4] and ribosomal DNA[3] of S. pastorianus appear to be derived from S. bayanus rather than S. cerevisiae.

The genomic difference between S. pastorianus and S. cerevisiae is responsible for a number of phenotypic traits which S. pastorianus share with S. bayanus, but not S. cerevisiae. The ability of S. pastorianus to break down melibiose is dependent on up to ten MEL genes, which are exclusive to strains metabolising melibose such as S. bayanus. S. pastorianus never grows above 34°C, whereas S. cerevisiae will grow at 37°C. S. pastorianus exhibits a higher growth rate than S. cerevisiae at 6 to 12°C.

It has been suggested that S. pastorianus may be a hybrid of S. cerevisiae and Saccharomyces monacensis, as the LEU2, MET2 and ACB1 genes of S. pastorianus had been reported to have a high level of similarity or be identical to the S. monacensis homologues [5][6][7]. However, subtelomeric sequence hybridisation has suggested that S. monacensis is likely to be a closely related hybrid to S. pastorianus, rather than an ancestor[1].

Ale strains are genetically more diverse than lager strains, as lager strains are thought to derive from a hybrid gene pool (Casey, 1996). It is thought that the lager strains in use are derived from only one or two primary strains; Tuborg and Carlsberg (Casey, 1990; Casey, 1996).


Saccharomyces uvarum

Saccharomyces uvarum is a species of yeast that is believed to originate as a hybrid of S. cerevisiae and S. monacensis, because of its allopolyploid genome[citation needed]. It is a bottom-fermenting yeast, so-called because it does not form the foam on top of the wort that top-fermenting yeast does.

Further research was done by Martinus Willem Beijerinck in 1898, it was synonymized with S. bayanus but revived by Nguyen & Gaillardin in 2005.[8][9]

See also

  • Brewing
  • Bottom and top fermenting yeast
  • Lager
  • Yeast

References

  1. ^ a b Casaregola S, et al. (2001), Analysis of the constitution of the beer yeast genome by PCR, sequencing and subtelomeric sequence hybridization., Int J Syst Evol Microbiol 51(Pt 4):1607-18.
  2. ^ Tamai Y, Momma T, Yoshimoto H, Kaneko Y., Co-existence of two types of chromosome in the bottom fermenting yeast, Saccharomyces pastorianus., Yeast. 1998 Jul;14(10):923-33.
  3. ^ a b c Montrocher R et al (1998), Phylogenetic Analysis of the Saccharomyces cerevisiae Group Based on Polymorphisms of the rDNA Spacer Sequences, Int. J. Syst. Bacteriol., vol 48, pp 295–303
  4. ^ Piskur, J., S. Smole, C. Groth, R.F. Petersen and M.B. Pedersen (1998), Structure and genetic stability of mitochondrial genomes vary among yeasts of the genus Saccharomyces. Int. J. System. Bacteriol. 48: 1015-1024.
  5. ^ Hansen J and Kielland-Brandt MC (1994), Saccharomyces carlsbergensis contains two functional MET2 alleles similar to homologues from S. cerevisiae and S. monacensis. Gene 140(1):33-40
  6. ^ Casey GP, Pedersen MB (1988), DNA sequence polymorphisms in the genus Saccharomyces. V. Cloning and characterization of a LEU2 gene from S. carlsbergensis. Carlsberg Res Commun 53(3):209-19
  7. ^ Borsting C, et al. (1997),Saccharomyces carlsbergensis contains two functional genes encoding the acyl-CoA binding protein, one similar to the ACB1 gene from S. cerevisiae and one identical to the ACB1 gene from S. monacensis. Yeast 13(15):1409-21
  8. ^ H. V. Nguyen & C. Gaillardin, Evolutionary relationships between the former species Saccharomyces uvarum and the hybrids Saccharomyces bayanus and Saccharomyces pastorianus; reinstatement of Saccharomyces uvarum (Beijerinck) as a distinct species., FEMS Yeast Research (2005) vol 5, pp 471–483
  9. ^ [http://www.epa.gov/oppt/biotech/pubs/fra/fra010.htm Saccharomyces uvarum at EPA.gov
 
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Saccharomyces_pastorianus". A list of authors is available in Wikipedia.
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