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FIRST-GENERATION FERMENTATION METABOLOMICS BY GC-MS: ESTABLISHMENT OF ANALYSIS METHODOLOGY

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The fermentation process performed by Saccharomyces cerevisiae has great importance for ethanol production. Therefore, a full understanding of yeast physiology during fermentation is critical to obtain better results in the process. The present work aimed to establish an extracellular metabolome methodology accessed by gas chromatography mass spectrometry (GC-MS) to study yeast physiology during fermentation. Thus, cell recycle fed-batch fermentations were performed with S. cerevisiae CAT-1. Metabolite wine extraction generated polar and nonpolar phases and each one was processed in different volumes. The parameters of GC-MS analysis were tested based on different works, two that focused on yeast metabolome and one that focused on plant metabolome. To determine the best methodology, we considered: (1) Chromatographic peaks profile, (2) Number of identified metabolites and (3) Cost-benefit. Given these parameters, the best result was obtained with polar fraction, volume of 200 µL and, interesting, the GC-MS parameters adopt in the plant metabolome work. It was possible to report 242 metabolites, the majority classified as Unknown (43 %), followed by Organic oxygen compounds (18 %) and Organic acids and derivatives (16 %), important metabolites classes for yeast fermentation. With this methodology, many studies can be made regarding yeast physiology under different fermentation conditions.