Maltotriose fermentation by Saccharomyces cerevisiae

Area of Science:

• Biochemistry and Molecular Biology
• Yeast Fermentation
• Industrial Microbiology

Background:

• Maltotriose is a significant sugar in brewer's wort, but its fermentation by industrial yeast strains is limited.
• Understanding the mechanisms of maltotriose utilization is crucial for optimizing brewing processes.
• Previous research indicates that some yeast strains respire rather than ferment maltotriose.

Purpose of the Study:

• To investigate the rate-limiting step in maltotriose fermentation by Saccharomyces cerevisiae.
• To compare active transport and intracellular hydrolysis of maltotriose in different yeast strains.
• To identify factors influencing maltotriose utilization in industrial yeast.

Main Methods:

• Isolation of a novel yeast strain capable of fermenting maltotriose in the presence of antimycin A.
• Detailed kinetic analysis of active maltotriose transport across the plasma membrane.
• Assessment of intracellular maltotriose hydrolysis rates and alpha-glucosidase activity.

Main Results:

• Both maltotriose-fermenting and non-fermenting yeast strains exhibited similar intracellular hydrolysis kinetics.
• Yeast cells do not appear to synthesize a specific maltotriose alpha-glucosidase.
• The maltotriose-fermenting strain demonstrated equal active transport rates for maltose and maltotriose, unlike the non-fermenting strain.

Conclusions:

• Active transport across the plasma membrane is the rate-limiting step for maltotriose fermentation in Saccharomyces cerevisiae.
• Differences in maltotriose transport efficiency, not intracellular hydrolysis, distinguish fermenting from non-fermenting yeast strains.
• This finding provides insights into optimizing yeast strains for efficient sugar utilization in industrial applications.