Increased salt tolerance in Zymomonas mobilis strain generated by adaptative evolution

Area of Science:

• Microbiology
• Biotechnology
• Biofuel Production

Background:

• Zymomonas mobilis is a key ethanologenic bacterium for bioethanol production.
• Industrial application is limited by Z. mobilis's sensitivity to saline stress.
• Developing salt-tolerant strains is crucial for efficient biocatalysis.

Purpose of the Study:

• To engineer salt-tolerant Zymomonas mobilis strains.
• To overcome limitations in industrial bioethanol production due to salinity.
• To enhance Z. mobilis resilience for robust biocatalysis.

Main Methods:

• Laboratory adaptive evolution with cell morphology-biased selection.
• Cultivation in media supplemented with 0.225 M NaCl.
• Comparative metabolomics and whole-genome sequencing.

Main Results:

• Evolved Z. mobilis strains showed improved growth and ethanol production under saline stress.
• Prototypical osmolytes like proline were not accumulated to counter salt stress.
• Disruption of the ZZ6_1149 gene encoding a carboxyl-terminal protease correlated with improved salt tolerance.

Conclusions:

• Successfully generated Z. mobilis strains capable of growth and fermentation in saline conditions.
• Cell shape-based diagnosis and selection is a viable strategy for Z. mobilis strain engineering.
• The developed strains offer potential for more efficient industrial bioethanol production.