Enhanced polymalic acid production from the glyoxylate shunt pathway under exogenous alcohol stress

Area of Science:

• Microbiology
• Biotechnology
• Biochemistry

Background:

• Polymalic acid (PMA) is a water-soluble biopolymer produced by Aureobasidium pullulans.
• Understanding microbial responses to environmental stress is crucial for optimizing biopolymer production.

Purpose of the Study:

• To investigate the physiological response of A. pullulans to exogenous alcohol stress.
• To identify genes involved in PMA production under stress conditions.
• To enhance PMA yield through metabolic engineering.

Main Methods:

• Exposure of A. pullulans to exogenous alcohols, specifically ethanol.
• Identification and analysis of the stress-responsive malate synthase (mls) gene.
• Construction of an engineered strain (YJ-MLS) overexpressing the mls gene.
• Batch fermentation in a 5-L fermentor to determine PMA titer and productivity.

Main Results:

• Ethanol stress effectively induced enhanced PMA yield, despite slight inhibition of cell growth.
• The malate synthase (mls) gene, involved in the glyoxylate shunt, was identified as being regulated by ethanol stress.
• The engineered YJ-MLS strain showed a 16.2% increase in PMA titer compared to the wild-type.
• A high PMA titer of 40.0 ± 0.38 g/L was achieved with the YJ-MLS strain under optimal conditions, with a peak productivity of 0.56 g/L/h.

Conclusions:

• Ethanol stress can be utilized as an effective inducer for boosting PMA production in A. pullulans.
• Overexpression of the malate synthase gene strengthens carbon metabolic flow towards PMA synthesis.
• This study provides novel insights into the regulatory mechanisms of alcohol stress in eukaryotic microbes and offers a strategy for improving biopolymer yields.