"TAXONOMIC STUDIES ON THE GENUS PEDIOCOCCUS"

Abstract

A taxonomic study has been carried out on the pediococci collected from various mashes, wort, yeasts and beer, including authentic strains.
From a comparison of growth ranges toward pH and temperature, degree of oxygen-requirement, halophility, fermentable sugars, salt- and hop-tolerancy, the genus Pediococcus is classified into five species, namely Pediococcus cerevisiae, P. acidilactici, P. pentosaceus, P. halophilus and P. urinae-equi.
The species "P. urinae-equi" including strains isolated from the horse-urine which has been sometimes considered as an origin of "beer-sarcina" is found to be difinitely different from the beer-pediococci which are anaerophilic with an absolute requirement of CO₂ for growth, incapableof growing in alkaline media or at a temperature of 35°, and have a high tolerancy for hop-antiseptic.
Although BALCKE did not give a complete taxonomic description on his species "P. cerevisiae", of which name was originally adopted by him for beer-sarcina, we have regarded that the beer-pediococci belong to P. cerevisiae (cerevisiae means beer in Latin).
Contrary to the opinion of PEDERSON et al. (14, 15), the strains distributed in fermenting vegetables are found to have many properties different from the beer-pediococci, i.e., maximum growth pH and temperature, hoptolerancy and CO₂-requirement etc. Thus we think it is better to include them into the species P. pentosaceus MEES rather than P. cerevisiae.
Other beer-sarcina strains labeled as P. damnosus, the name which has been adopted mainly by brewery researchers, may be included in the species of P. cerevisiae except P. damnosus strain No. 904 & 908 which have the same properties of P. pentosaceus.
Although we do not know about the history or the origin of the strains, 904 & 908, the question arises as to an occurrence of the mutation from P. cerevisiae to P. pentosaceus. Experiments to examine such a possibility have not yet been succeeded at present.
In any way, the habitat of the beer-pediococci incapable of growing in alkaline media is entirely unknown except beer and brewer's yeasts.
The acid sensitive strains of Pediococcus soyae which have been recently isolated from soy-mashes in Japan are characterized by their strong salt-tolerancy and halophility. However, since they show nearly the same taxonomic properties with the strain "P. halophilus MEES (1934)" isolated from anchovy pickles, the authors have regarded them as a variety of the species "P. halophilus."
We wish to warn that strains nowadays labeled as Streptococcus citrovorus or Leuconostoc citrovorum must not be classified into such genera, but should be considered as a variety of P. pentosaceus, and also the strain "Leuconostoc mesenteroides P-60 ATCC 8042" should be included in the species of P. acidilactici.
Differing from the description appearing in BERGEY's Manual, the acid sensitive pediococci produce dextro-rotatory lactic acid in stead of the racemic form. This may be comprehended as an extreme case of restricted racemiase formation.