Classification of Saccharomyces boulardii
Historically: Saccharomyces boulardii was a species
Saccharomyces [genus] boulardii [species]
Modern day: Saccharomyces boulardii is most likely a strain of the Saccharomyces cerevisiae species
Saccharomyces [genus] cerevisiae [species] var boulardii [strain]
Saccharomyces boulardii as a species or subspecies
Can the taxonomy go further than the term ‘Saccharomyces boulardii’?
When it comes to the nomenclature of a probiotic Wren Laboratories Ltd regards the name of the strain as the most salient information for trade and consumers. This is because, even within a single species, there can be large variations between different strains of probiotics in terms of their physical properties. Wren Labs Ltd has always had a strong ethos of transparency with the end consumer; informing the consumer as much as possible with regards to the nature of the ingredients in each product. With regards to nomenclature and classification of microorganisms in the OptiBac Probiotics range, the strain name of each microorganism is always listed, on all packs and marketing materials. This is more detailed than the majority of other probiotics on the market, where simply the genus and species name are listed, and not the name of the strain.8 As explored in the previous section, in Saccharomyces boulardii, the term ‘boulardii’ indicates the strain, and therefore the most specific part of the name.
Occasionally additional letters and numbers appear after the strain name, for example S. boulardii MTCC 5375; in this case ‘MTCC 5375’ is the reference number for the microbiology bank in which the strain is deposited. It is not necessary to include the bank reference name on the packaging of this product, as it does not provide the consumer with any additional information on the qualities and characteristics of the product. Similarly, Wren Laboratories Ltd does not include the bank reference number on any other microorganisms in the range, and very few, if any, other companies seem to include the bank reference number on packaging or any consumer-facing materials.
Another type of classification which can follow the strain name is the name given to a particular microorganism by a manufacturer eg. ‘Unique 28’. Again, we deem this additional information insignificant (and unnecessary for the consumer) in terms of identity and characteristics of the microorganism; it simply denotes the laboratory from which this microorganism originates.
It is fairly common to find S. boulardii with different bank reference numbers or manufacturing names on the market. For example,the one used by Wren Laboratories Ltd is S. boulardii CNCM I-1079, supplied by Institut Rosell Lallemand. The first S. boulardii to ever be isolated has the reference number Hansen CBS 5926, and is supplied by Biocodex. Other high quality S. boulardii microorganisms, including the type used by Wren Laboratories Ltd, since then have shown a high level of similarity if not complete similarity to this original isolate, using both laboratory techniques to sequence the genome and clinical trials to indicate mechanism of actions in the body.
Also note that occurrences of Saccharomyces boulardii lyo refer to the lyophilisation of the probiotic and are not referring to a specific strain.
Omission of ‘cerevisiae’ in Saccharomyces boulardii
As aforementioned, the full name for S. boulardii is Saccharomyces cerevisiae var boulardii. At Wren Laboratories Ltd we do not include the species name (cerevisiae) for this product.
S. boulardii is a unique microorganism, by virtue that as a strain it has vastly different properties to other yeasts in the same S. cerevisiaespecies. For example, baker’s yeast and brewer’s yeast, which are also in the S. cerevisiae species, are known to invoke intolerances in some people.10 Inclusion of the species name in this case could result in consumer confusion – as consumers might understand the OptiBac Probiotics S. boulardii to be the same as brewer’s yeast, which is not the case. This is perhaps why, in fact, S. boulardii was previously classified as a separate species – as it has such different properties to the S. cerevisiae species. It may be worth noting that certain experts in the field of microbiology still believe S. boulardii should be classified separately to ‘cerevisiae’.11 Furthermore, for the vast majority of S. boulardii on the market, the species name ‘cerevisiae’ is not listed on packaging and information material.12
Having reviewed scientific papers (both regarding classification in particular, as well as clinical trials examining the effect of S. boulardii) Wren Laboratories Ltd understands S. boulardii to be a strain of yeast, and believes that in the full name Saccharomyces cerevisiae var boulardii, the term ‘var’ is interchangeable with ‘strain’. In an effort to present the most scientifically correct nomenclature, as well as in order to minimise any consumer confusion, Wren Laboratories Ltd does not include ‘cerevisiae’ on packaging or marketing materials, nor the bank reference number CNCM I-1079.