Enhancing polyhydroxyalkanoate production in Cupriavidus sp. L7L through wcaJ gene deletion

Area of Science:

• Microbiology
• Biotechnology
• Polymer Science

Background:

• Cupriavidus sp. L7L produces high-content polyhydroxyalkanoate (PHA).
• High medium viscosity during fermentation limits PHA production and cell harvesting.
• Extracellular polymeric substances (EPS) contribute to increased viscosity.

Purpose of the Study:

• To investigate the role of the wcaJ gene in EPS production and medium viscosity.
• To develop a non-mucoid variant of Cupriavidus sp. L7L for improved fermentation.
• To enhance polyhydroxyalkanoate (PHA) production and downstream processing.

Main Methods:

• Isolation of a non-mucoid variant using a mini-Tn5 mutant library.
• Gene deletion of wcaJ and complementation experiments.
• Fed-batch fermentation of wild-type and mutant strains using levulinate (Lev).
• Measurement of PHA content, monomer composition, EPS content, and medium viscosity.

Main Results:

• Deletion of wcaJ eliminated mucoid colony formation and significantly reduced EPS content and medium viscosity.
• Cupriavidus sp. L7L∆wcaJ showed a 42% increase in PHA concentration after extended fermentation.
• Cell collection via centrifugation was significantly easier for the deletion strain.
• Lev-to-PHA conversion efficiency was improved in the deletion strain.

Conclusions:

• The wcaJ gene is crucial for EPS production and high viscosity in Cupriavidus sp. L7L.
• Cupriavidus sp. L7L∆wcaJ offers a promising platform for efficient and scalable polyhydroxyalkanoate (PHA) production.
• Genetic modification to reduce EPS is a viable strategy for overcoming fermentation challenges in biopolymer production.