Biotransformation of trichothecene mycotoxins during fermentation with lager yeast

Food and beverage processing may convert mycotoxins into conjugated 'modified mycotoxins' rendering them undetectable with routine analytical methods. The aim here was to investigate the metabolic fate of Fusarium trichothecene mycotoxins including HT-2, T-2, as well as deoxynivalenol and its modified form deoxynivalenol-3-glucoside during fermentation by lager yeast. Mycotoxins were dosed at varying concentrations or in different combinations to 11.5°Plato wort that was used in the simulated brewing experiments. Yeast was tolerant to mycotoxins at concentrations up to 10 ppm. Thus, the presence of trichothecenes, even at levels far in excess of those found in naturally contaminated barley, had little or no effect on sugar utilisation, alcohol production, pH, yeast growth or cell viability. Wort and yeast biomass samples that were collected at pre-defined timepoints (0-96 h) were analysed by LC-QTOF-MS to examine the kinetics of these compounds during fermentation and possible accumulation within yeast cells. Approx. 20% of toxin amounts were potentially biotransformed by yeast at the end of fermentation. Targeted metabolomics were performed on the raw full-scan LC-QTOF-MS data with Waters MetaboLynx software to detect any metabolic products formed by yeast following exposure to trichothecenes. Novel modified forms of trichothecene metabolites will be presented here that were confirmed by MS/MS measurements. A clearer understanding of how yeast interact with and transform mycotoxins during brewery fermentation is expected to improve our ability to detect and control the occurrence of these toxins in beer, thereby minimizing potential risks to the consumer.