Oxygen requirements of yeasts

Area of Science:

• Microbiology
• Yeast Physiology

Background:

• Yeast fermentation is crucial in various industries.
• Understanding anaerobic growth is key to optimizing yeast applications.
• Many yeasts are considered non-fermentative, but their anaerobic behavior is less understood.

Purpose of the Study:

• To investigate the anaerobic growth capabilities of 75 yeast genera.
• To identify yeast species that can thrive under strictly anaerobic conditions.
• To compare the anaerobic performance of different yeast species, including Saccharomyces cerevisiae.

Main Methods:

• Examined 75 yeast genera for anaerobic growth in complex and mineral media.
• Utilized resazurin as a redox indicator to define anaerobic conditions.
• Assessed glucose fermentation to ethanol in oxygen-limited shake-flask cultures.
• Quantified growth rates (μmax) under anaerobic conditions for selected strains.

Main Results:

• All tested yeast strains fermented glucose to ethanol under oxygen limitation.
• Only 23% of the yeast species exhibited growth under strict anaerobic conditions.
• Saccharomyces cerevisiae demonstrated superior rapid growth at low redox potentials.
• Torulaspora delbrueckii and Candida tropicalis showed poor anaerobic growth but high fermentation rates.

Conclusions:

• A significant portion of yeast species possess previously unrecognized oxygen requirements for growth.
• Saccharomyces cerevisiae is highly adapted for anaerobic growth compared to other tested yeasts.
• Anaerobic cultivation success varies greatly among yeast genera, necessitating specific strain selection.