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

Inhaltsverzeichnis (Table of Contents)

• Resume
• Chapter 1: Introduction
• Chapter 2: Materials and Methods
• Chapter 3: Results
• Chapter 4: Discussion
• Chapter 5: Conclusions

Zielsetzung und Themenschwerpunkte (Objectives and Key Themes)

This thesis investigates the influence of different nitrogen sources on fermentation and higher alcohol production by an industrial strain of Saccharomyces cerevisiae. The primary objective is to determine the effect of various nitrogen sources (ammonium, leucine, isoleucine, valine, tryptophan, and phenylalanine) on fermentation kinetics, gene transcription, and the production of higher alcohols, ultimately impacting the flavor profile of alcoholic beverages.

• Effect of nitrogen source on fermentation performance
• Impact of nitrogen source on higher alcohol production
• Analysis of gene transcription patterns related to higher alcohol biosynthesis
• Metabolic pathways involved in higher alcohol formation
• Potential for manipulating nitrogen sources to improve beverage quality

Zusammenfassung der Kapitel (Chapter Summaries)

Resume: This section provides a concise overview of the thesis, highlighting the main findings and conclusions. The study used an industrial strain of S. cerevisiae (JP1) and a laboratory strain (CEN.PK113) to analyze the effects of different nitrogen sources on fermentation, gene expression, and higher alcohol production. Ammonium sulfate and valine showed superior fermentation performance, while amino acid sources led to higher alcohol production (300-1000 mg/L). The study also observed unexpected higher alcohol production, potentially due to amino acid catabolism overflow and metabolic byproducts. The findings suggest the possibility of manipulating nitrogen sources to control higher alcohol levels and improve the sensory qualities of alcoholic beverages.

Chapter 1: Introduction: This chapter introduces the importance of higher alcohols in the organoleptic profile of alcoholic beverages and the influence of nitrogen sources on their production in Saccharomyces cerevisiae. The use of ammonium salts in industrial processes is highlighted, along with the limited research on this aspect. The chapter outlines the study's objectives and methodology.

Chapter 2: Materials and Methods: This chapter describes the experimental design, including the yeast strains used (industrial strain JP1 and laboratory strain CEN.PK113), the culture media with different nitrogen sources (ammonium sulfate, leucine, isoleucine, valine, tryptophan, and phenylalanine), and the analytical methods employed to assess fermentation kinetics, gene expression, and higher alcohol production. The chapter details the techniques used to measure growth rates, glucose consumption, ethanol production, acetate production and the various higher alcohols.

Chapter 3: Results: This chapter presents the experimental findings. The kinetic results demonstrate differences in growth rates (μmax) and doubling times (td) depending on the nitrogen source, with ammonium sulfate and valine showing the best performance. Different nitrogen sources also resulted in varying levels of higher alcohol production. Specific examples of higher alcohol concentrations (mg/L) for each condition are presented and discussed. The results also include the analysis of gene transcription and unexpected higher alcohol accumulation.

Chapter 4: Discussion: This chapter interprets the results, explaining the mechanisms underlying the observed effects of nitrogen sources on fermentation and higher alcohol production. The chapter discusses the Ehrlich pathway and its relationship with higher alcohol formation. The unexpected production of higher alcohols not directly derived from the Ehrlich pathway is thoroughly analyzed, proposing potential explanations such as overflow metabolism, amino acid leakage, and the role of mitochondrial compartmentalization. The synergistic effects of nitrogen concentration and de novo synthesis are also discussed.

Schlüsselwörter (Keywords)

Saccharomyces cerevisiae, fermentation, higher alcohols, nitrogen source, amino acids, Ehrlich pathway, gene transcription, cachaça, organoleptic compounds, metabolic engineering.

Häufig gestellte Fragen

What is the main topic of this language preview?

This language preview provides information about a thesis investigating the influence of different nitrogen sources on fermentation and higher alcohol production by Saccharomyces cerevisiae.

What are the key themes explored in the thesis?

The key themes include the effect of nitrogen source on fermentation performance, the impact of nitrogen source on higher alcohol production, analysis of gene transcription patterns related to higher alcohol biosynthesis, metabolic pathways involved in higher alcohol formation, and the potential for manipulating nitrogen sources to improve beverage quality.

What are the objectives of the thesis?

The primary objective is to determine the effect of various nitrogen sources (ammonium, leucine, isoleucine, valine, tryptophan, and phenylalanine) on fermentation kinetics, gene transcription, and the production of higher alcohols, ultimately impacting the flavor profile of alcoholic beverages.

What are the main chapters of the thesis?

The thesis is structured into five main chapters: Resume, Introduction, Materials and Methods, Results, and Discussion, and Conclusions.

What does the Resume section contain?

The Resume provides a concise overview of the thesis, highlighting the main findings and conclusions regarding the effects of nitrogen sources on fermentation, gene expression, and higher alcohol production.

What is discussed in the Introduction chapter?

The Introduction introduces the importance of higher alcohols in the organoleptic profile of alcoholic beverages and the influence of nitrogen sources on their production in Saccharomyces cerevisiae. It also outlines the study's objectives and methodology.

What information is included in the Materials and Methods chapter?

The Materials and Methods chapter describes the experimental design, including the yeast strains used, the culture media with different nitrogen sources, and the analytical methods employed to assess fermentation kinetics, gene expression, and higher alcohol production.

What types of results are presented in the Results chapter?

The Results chapter presents the experimental findings regarding the impact of different nitrogen sources on growth rates, higher alcohol production, and gene transcription. It includes specific examples of higher alcohol concentrations for each condition.

What topics are covered in the Discussion chapter?

The Discussion chapter interprets the results, explaining the mechanisms underlying the observed effects of nitrogen sources on fermentation and higher alcohol production. It discusses the Ehrlich pathway and its relationship with higher alcohol formation, as well as potential explanations for unexpected higher alcohol production.

What are the keywords associated with this research?

The keywords include Saccharomyces cerevisiae, fermentation, higher alcohols, nitrogen source, amino acids, Ehrlich pathway, gene transcription, cachaça, organoleptic compounds, and metabolic engineering.