Toxicity of various kinds of ionic liquids towards the cell growth and end product formation of the probiotic strain, Propionibacterium freudenreichii†
This paper reports on an investigation into the toxicity of various kinds of 1-alkyl-3-methylimidazolium ionic liquids (ILs) including [BMIM][BF4], [HMIM][BF4], [BMIM][PTS], [HMIM][PTS], [BMIM][NO3], [HMIM][NO3], [OMIM][NO3], [BMIM][MeOSO3], [OMIM][MeOSO3], [BMIM][SCN], [OMIM][SCN], towards the cell growth of a probiotic strain Propionibacterium freudenreichii subsp. freudenreichii; in addition, the effects of ILs on the production of intracellular vitamin B12 (VB12) and extracellular propionic acid (PA) by the mentioned strain were investigated for the first time. The results of the study demonstrated that all ILs were toxic towards the microorganism in concentrations above 1% (w/v). The most toxic IL among them, however, was [OMIM][NO3] which inhibited the cell growth at even low concentrations of 0.005% (w/v). The inhibitory concentration after 48 h (IC50-48 h) for this IL was 0.005% (w/v). The least toxic IL was [BMIM][PTS] with IC50-48 h corresponding to 1% (w/v). Production of PA was related to the concentration of IL. However, a complex relation between production of intracellular product, VB12, and the amount of IL in the broth was observed. The information in this paper could be useful for researchers who work in the fields of extractive fermentation, ionic liquid extraction and environmental pollution.