Hello, my name is Debaryomyces hansenii

Eureka, we are back to spoilage yeasts. Today, I would like to introduce another spoilage yeast called Debaryomyces hansenii (anamorph Candida famata). This yeast was originally isolated from saline environments and is maybe one of the most osmotolerant (can tolerate high levels of salt and sugar) yeasts in existence [Kumar, 2012]. This yeast is very common in various food products and has a big biotechnological potential. It is therefore of no surprise that two strains of this yeast, CBS767 and MTCC 234, have been previously sequenced and their genomes are published [Lépingle, 2000; Kumar, 2012].

Older publications talk of two yeast varieties of D. hansenii: D. hansenii var. hansenii and D. hansenii var. fabryi with differences in their 26S rRNA gene as well as their temperature preferences [Breuer, 2006]. The current nomenclature reinstated D. fabryi as a separate family based on the genetical differences between the two varieties. I will therefore only discuss D. hansenii: D. hansenii var. hansenii in this post.

Where do I work?

D. hansenii is the most prevalent yeast in dairy and meat products as well as early stages of soy sauce fermentation [Kurtzman, 2011]. Various isolates exist originating from cheese, sake moto, edomiso, rennet, psoriasis, infected hands and salmon [Kurtzman, 2011]. In general, D. hansenii can be found in habitats with low water activity as well as in products with high sugar concentrations [Breuer, 2006]. Although D. hansenii is considered a non-pathogenic yeast, various clinical cases of D. hansenii exist.

What about beer?

I could not find a source discussing the use of D. hansenii in the production of beer.

What is so special about me?

As already mentioned, D. hansenii can tolerate very high levels of salt. Some sources cite salinity levels up to 24% whereas Saccharomyces cerevisiae commonly tolerate levels up to 10% [Lépingle, 2000]. Such high tolerances are not that common in living organisms and can be used on industrial scale by cultivating D. hansenii at high salt levels to prevent the growth of other yeasts (quasi non-sterile production conditions). Beside dealing with high osmolarities, D. hansenii secrete toxins capable of killing other yeasts [Breuer, 2006].

Although this yeast is already an extremophile in terms of osmolarity, it does not stop there. Besides the normal sugars, D. hansenii is capable of metabolizing n-alkanes, melibiose, raffinose, soluble starch, inositol, xylose, lactic acid and citric acid [Breuer, 2006; Lépingle, 2000; Kumar, 2012]. Furthermore, this yeast can form arabitol as well as riboflavin (vitamin B2) [Génolevures, 2014]. D. hansenii is therefore used on industrial scale to produce vitamin B2 and has a big potential for other biotechnological processes.

D. hansenii is a very common yeast in cheeses and seems to have a major impact on the development of the microflora as well as the taste [Lépingle, 2000]. As previously mentioned, D. hansenii can metabolize lactic acid, citric acid and galactose. The assimilation of lactic acid by yeasts has been shown to have an impact on the bacterial flora of the cheese in types such as Limburger, Tilsiter, Port Salut, Trappist, Brick and the Danish Danbo [Breuer, 2006]. Furthermore, D. hansenii forms volatile compounds associated with a “cheesy” flavor [Breuer, 2006]. For example, D. hansenii seems to have a major role in the development of Cheddar and Camembert cheese by synthesizing S-methylthioacetate (most prevalent volatile sulphur compound found in cheese) [Breuer, 2006].

Summarized, D.hansenii is involved in various dairy products and has some very unique biochemical properties. This makes this yeast very interesting for biotechnological processes such as the production of toxins as therapeutic agents, produce xylitol (as already discussed in the previous post about Pichia kudriavzevii), manufacturing chemical compounds and the production of vitamin B2.

As soon as a yeast gets interesting on industrial scale, a genome sequencing project gets commonly initiated to get more insight into the organism you want to deal with. However, very often such genomes do not get published to keep the obtained information a secret. Luckily for us, the two draft genomes of D. hansenii can be accessed by anyone.

D. hansenii strain CBS767 (isolated from Sherry in Denmark) has been sequenced by the Génolevure project. The obtained assembly consists of 7 chromosomes (assembly size of 12.2 Mb). 205 tRNA genes could be found corresponding to a set of 43 tRNAs. D. hansenii uses an alternative genetic code and uses the codon CAG for serine instead of leucine and carries a single copy tRNA-Ser CAG.

D. hansenii strain MTCC 234 (isolated from New Zealand soil) has been Illumina sequenced and assembled using Velvet 1.1.06 into a draft genome consisting of 542 contigs and a N50 contig length of 68,507 bp [Kumar, 2012]. The authors furthermore predicted 5,313 proteins and could find matches (E-value cutoff of 10-6) in the nr NCBI database for >99.5% of the predicted proteins.

Where can you find me?

In theory, it should be easy to pick up D. hansenii from dairy products if one follows the protocol mentioned in the section below.

Some biochemical stats about me for yeast ranchers

Breuer et al mention a simple protocol to pick up D. hansenii: Cultivate yeasts at 10% NaCl and 5% glucose to discriminate between D. hansenii and other ascomycetous yeasts. Below a summary of the biochemical properties of D. hansenii. Data is summarized from Kurtzman et al (2011).

Systematic name: Debaryomyces hansenii (anamorph Candida famata)
Synonyms: There are a lots of accepted synonyms for this yeasts. Just some examples: Saccharomyces hansenii, Debaryomyces gruetzii, Pichia hansenii
Growth in malt extract: Cell morphology: Spherical to short-ovoid form, 2-7 µm x 2-9 µm
Clustering: Occurring as single cells, pairs or short chains
Pseudohyphae: Poor formation
Pellicle formation: Not described
Growth in malt extract: Colony morphology: After 4 weeks: Grayish-white to yellowish, glistening or dull, butyrous and smooth or wrinkled
Fermentation: Glucose: Weak
Galactose: Weak
Sucrose: Weak
Maltose: Weak
Lactose: Negative
Raffinose: Weak
Trehalose: Weak

That’s all about Debaryomyces hansenii. In summary, Debaryomyces hansenii is involved in the maturation process of various food products such as cheese, sausages, various other fermented products as well as industrial applications such as the production of vitamin B2.

Although this extremophilic yeast sounds really interesting, I would not use D. hansenii as a single yeast species to ferment a beer. Simply because it is a very weak fermenter of maltose and glucose, the main sugars present in wort. On the other hand, one can only guess its impact if used as a secondary or bottling strain. Maybe use this yeast for a Imperial Gose with a salt content of about 20%? Let me know if there is someone crazy enough to make such a big Imperial Gose similar to sea water…

Bibliography

  • Breuer U, Harms H (2006) Debaryomyces hansenii – an extremophilic yeast with biotechnological potential. Yeast, Vol 23, p.415-437
  • Génolevures, Debaryomyces hansenii entry (via http://genolevures.org/deha.html), accessed April 2014
  • Kumar S, Randhawa A, Ganesan K, Raghava SG, Mondal AK (2012) Draft Genome Sequence of Salt-Tolerant Yeast Debaryomyces hansenii var. hansenii MTCC 234. Eukaryotic Cell, Vol11(7), p.961-962, (via NCBI)
  • Kurtzman CP, Fell JW, Boekhout T (2011) The Yeasts, a Taxonomic Study. Volume 1. Fifth edition. Elsevier (Link to sciencedirect)
  • Lépingle A, Casaregola S, Neuvéglise C, Bon E, Nguyen HV, Artiguenave F, Wincker P, Gaillardin C (2000) Genomic Exploration of the Hemiascomycetous Yeasts: 14. Debaryomyces hansenii var. hansenii. FEBS Letters, Vol 487, p.82-86
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