Engineering redox cofactor regeneration for improved pentose fermentation in Saccharomyces cerevisiae

Area of Science:

• Biotechnology
• Metabolic Engineering
• Synthetic Biology

Background:

• Pentose fermentation to ethanol by Saccharomyces cerevisiae is inefficient due to redox cofactor imbalances.
• D-xylose and L-arabinose catabolism requires regeneration of NADPH and NAD+.
• Natural NADPH regeneration via the pentose phosphate pathway produces CO2 and NAD+ imbalance.

Purpose of the Study:

• To enhance pentose fermentation to ethanol by improving NADPH regeneration in Saccharomyces cerevisiae.
• To investigate the role of NADP+-dependent D-glyceraldehyde-3-phosphate dehydrogenase (NADP-GAPDH) in D-xylose fermentation.
• To optimize redox cofactor balance for increased ethanol yield and fermentation rate.

Main Methods:

• Engineered Saccharomyces cerevisiae with D-xylose pathway.
• Expressed the NADP+-dependent D-glyceraldehyde-3-phosphate dehydrogenase (GDP1) gene.
• Deleted the glucose-6-phosphate dehydrogenase (ZWF1) gene.
• Anaerobic fermentation of D-xylose.

Main Results:

• Expression of GDP1 increased D-xylose fermentation rate and ethanol yield.
• GDP1 expression reduced xylitol and CO2 byproduct formation.
• Deletion of ZWF1 combined with GDP1 overexpression further enhanced fermentation performance.
• Engineered yeast shifted from producing xylitol and CO2 to primarily ethanol.

Conclusions:

• Engineering redox cofactor regeneration is crucial for efficient pentose fermentation.
• NADP+-dependent D-glyceraldehyde-3-phosphate dehydrogenase (GDP1) is a viable strategy for improving NADPH regeneration.
• Genetic modification of redox pathways can convert yeast strains for enhanced ethanol production from pentoses.