Breeding bafilomycin A1-resistant sake yeast to improve fermentative capacity.

Area of Science:

• Microbiology
• Biotechnology
• Food Science

Background:

• Sake yeast fermentation is crucial but often faces challenges with flavor modification or capacity enhancement.
• Current breeding methods for sake yeast can lead to trade-offs, such as reduced fermentative capacity or increased acidity.
• Improving yeast fermentative capacity while controlling acidity is a key goal in sake production.

Purpose of the Study:

• To enhance sake yeast fermentative capacity.
• To limit the increase in sake acidity during fermentation.
• To investigate the role of vacuolar-type ATPase (V-ATPase) activity in yeast fermentative performance.

Main Methods:

• Sake yeast strains were subjected to ultraviolet mutagenesis and selection for resistance to bafilomycin A1 (Baf), a V-ATPase inhibitor.
• Baf-resistant strains were analyzed for changes in growth rate, cell and vacuolar morphology, vacuolar acidity, and intracellular ATP levels.
• Brewing characteristics of selected strains were evaluated for fermentative capacity, acidity, and amino acid content.

Main Results:

• Baf-resistant sake yeast strains showed no significant changes in growth, cell, or vacuolar morphology.
• These strains exhibited increased vacuolar acidity and decreased intracellular ATP levels, indicating enhanced V-ATPase activity.
• Selected strains demonstrated improved fermentative capacity without an increase in acidity or amino acid content.

Conclusions:

• Developing Baf-resistant sake yeast strains is a viable strategy to enhance fermentative capacity.
• Reduced intracellular ATP levels, achieved through enhanced V-ATPase activity, correlate with improved fermentation efficiency.
• This approach offers a method to improve sake brewing without compromising product quality by increasing acidity.