D-lactic acid production by metabolically engineered Saccharomyces cerevisiae

Area of Science:

• Biotechnology
• Polymer Science
• Microbial Engineering

Background:

• Poly D-lactic acid enhances poly L-lactic acid thermostability via stereo complex formation.
• Efficient D-lactic acid production is crucial for advanced polymer applications.
• Current methods for lactic acid production face challenges in purity and process efficiency.

Purpose of the Study:

• To engineer Saccharomyces cerevisiae for efficient D-lactic acid production.
• To develop a cost-effective and high-yield method for producing pure D-lactic acid.
• To explore a novel production pathway for D-lactic acid without neutralization.

Main Methods:

• Metabolic engineering of Saccharomyces cerevisiae by deleting pyruvate decarboxylase 1 (PDC1).
• Introduction of two copies of the D-lactate dehydrogenase (D-LDH) gene from Leuconostoc mesenteroides.
• Fermentation under both neutralizing and non-neutralizing conditions to assess D-lactate yield and purity.

Main Results:

• Achieved D-lactate production of 61.5 g/l under neutralizing conditions.
• Demonstrated a glucose transformation efficiency of 61.2% to D-lactic acid.
• Obtained a free D-lactic acid yield of 53.0% under non-neutralizing conditions with purity exceeding 99.9%.

Conclusions:

• Engineered yeast provides an efficient platform for high-purity D-lactic acid production.
• The developed method offers a novel, neutralization-free approach for D-lactic acid synthesis.
• This strategy presents a viable alternative to existing methods using lactic acid bacteria or transgenic E. coli.