Metabolic analysis of S. cerevisiae strains engineered for malolactic fermentation

Area of Science:

• Enology and Fermentation Science
• Molecular Biology
• Biotechnology

Background:

• Malolactic fermentation (MLF) is crucial for wine quality, reducing acidity and enhancing stability.
• Implementing MLF in yeast strains requires efficient malate transport and enzymatic conversion.
• Genetic engineering offers a pathway to enhance MLF capabilities in Saccharomyces cerevisiae.

Purpose of the Study:

• To engineer Saccharomyces cerevisiae for efficient malolactic fermentation.
• To investigate the role of malate permease and malolactic enzyme expression levels on MLF kinetics.
• To assess the metabolic impact of engineered MLF under enological conditions.

Main Methods:

• Coexpression of Lactococcus lactis malolactic enzyme (mleS) and Schizosaccharomyces pombe malate permease (mae1) genes in Saccharomyces cerevisiae.
• Utilizing yeast promoters to control gene expression levels.
• Monitoring malate degradation kinetics and metabolic byproducts under simulated enological conditions.

Main Results:

• Complete malolactic fermentation was achieved in engineered Saccharomyces cerevisiae strains.
• Malate permease (mae1) expression level significantly influenced MLF reaction kinetics by regulating malate uptake.
• A specific strain (multiple mae1 copies, one mleS copy) degraded 3 g/l malate within 4 days via the malolactic pathway.
• No significant metabolic side effects were observed in the engineered strains.

Conclusions:

• Coexpression of mleS and mae1 enables efficient malolactic fermentation in Saccharomyces cerevisiae.
• Optimized expression of mae1 and mleS is critical for controlling MLF efficiency and kinetics.
• Engineered yeast strains provide a viable tool for targeted malate reduction in winemaking without adverse metabolic consequences.