High-resolution Growth Curves Monitored With the Cell Growth Quantifier Reveal Toxicity of M-cresol on S. cerevisiae Cells

M-cresol (3-methylphenol) holds significance in industrial applications as a flavor and platform chemical. It serves as a precursor for various substances, including menthol, and finds use in disinfectants and antiseptic agents due to its antibacterial and antifungal properties. In this study  the biotechnological production of m-cresol from sugar utilizing the yeast Saccharomyces cerevisiae was achieved.

Considering the expected toxicity of m-cresol on the yeast cells involved in its production, a toxicity test was conducted with S. cerevisiae cells exposed to different concentrations of m-cresol. 

Five distinct concentrations of m-cresol (150 mg/L, 300 mg/L, 450 mg/L, 600 mg/L, and 750 mg/L) were introduced into the yeast culture medium, alongside a negative control devoid of m-cresol (0 mg/L). Growth was monitored over a fermentation period of 144 hours using the Cell Growth Quantifier (CGQ). The high-resolution growth curves obtained from these parallel experiments clearly demonstrate the toxicity of m-cresol on yeast cells, with noticeable differences apparent among the various concentrations.

The performed toxicity test revealed that even at the lowest tested concentration of 150 mg/L, growth of the S. cerevisiae strain exhibited a slight reduction. Subsequently, growth rates were significantly diminished within the concentration range of 450–600 mg/L, and complete inhibition occurred at 750 mg/L of m-cresol. In summary, m-cresol demonstrates notable toxicity towards S. cerevisiae. This toxicity was effectively visualized through high-resolution growth curves using the Cell Growth Quantifier. The non-invasive, online measurement facilitated a streamlined and parallelized experiment involving 12 flasks (with 6 replicates of m-cresol concentrations), eliminating the need for manual sampling.