Influence of nitrogen source on fermentation and higher alcohol production by an industrial strain of Saccharomyces cerevisiae: The Isoleucine case

Doctoral Thesis / Dissertation from the year 2012 in the subject Biology - Genetics / Gene Technology, Federal Rural University of Pernambuco (Institut National des Sciences Appliquées), course: Genetics, language: English, abstract: Uncover the secrets behind crafting the perfect flavor in alcoholic beverages! Delve into the intricate world of Saccharomyces cerevisiae and its metabolic dance with nitrogen, where the choice of nutrient becomes the conductor of fermentation. This groundbreaking study meticulously examines how different nitrogen sources-from the common ammonium to the complex amino acids like leucine, isoleucine, valine, tryptophan, and phenylalanine-orchestrate the production of higher alcohols, those enigmatic compounds that define the very essence of a drink's aroma and taste. Journey through meticulously designed experiments using both industrial (JP1) and laboratory (CEN.PK113) strains to witness firsthand the profound impact of nitrogen on fermentation kinetics, unveiling how growth rates and doubling times are dramatically influenced by nutrient selection. Explore the fascinating Ehrlich pathway, the established route to higher alcohol formation, while simultaneously unraveling the mysteries behind unexpected alcohol production, potentially linked to metabolic overflow, amino acid leakage, and the hidden roles of mitochondrial compartments. This research dives deep into gene transcription patterns, providing a molecular-level understanding of how nitrogen dictates the expression of genes crucial for higher alcohol biosynthesis, opening avenues for precision metabolic engineering. Discover how manipulating nitrogen sources can become a powerful tool for controlling higher alcohol levels, ultimately shaping the sensory profile of beverages like cachaça and beyond. With detailed analysis of growth rates, glucose consumption, ethanol and acetate production, and the quantification of various higher alcohols, this thesis provides invaluable insights for optimizing fermentation processes and enhancing the organoleptic qualities of alcoholic beverages. Explore the potential for tailoring nitrogen inputs to achieve desired flavor profiles, paving the way for innovative strategies in the alcoholic beverage industry. This investigation not only sheds light on the intricate relationship between nitrogen, fermentation, and flavor but also offers a roadmap for future research and development in the pursuit of crafting beverages with unparalleled sensory appeal. Keywords: Saccharomyces cerevisiae, fermentation, higher alcohols, nitrogen source, amino acids, Ehrlich pathway, gene transcription, cachaça, organoleptic compounds, metabolic engineering, flavor, aroma, beverage quality.