Boosting Astaxanthin in E. coli via Fermentation Optimization and Enzyme Self-Assembly

Area of Science:

• Synthetic biology
• Metabolic engineering
• Biochemical engineering

Background:

• Astaxanthin is a valuable carotenoid with significant antioxidant properties.
• Efficient microbial production of astaxanthin is crucial for its commercial applications.
• Engineering Escherichia coli offers a promising platform for carotenoid biosynthesis.

Purpose of the Study:

• To intensify astaxanthin biosynthesis in engineered Escherichia coli.
• To optimize fermentation conditions using statistical design and predictive modeling.
• To enhance astaxanthin production through modular enzyme self-assembly.

Main Methods:

• Utilized single-factor screens and L9 (3^4) orthogonal design to optimize fermentation parameters (cultivation time, temperature, agitation, IPTG concentration).
• Employed a back-propagation neural network (BPNN) for accurate prediction of astaxanthin titres.
• Repurposed orthogonal docking-domain pairs from type I trans-AT polyketide synthases for enzyme co-localization.

Main Results:

• Identified an optimal fermentation operating point (36 h, 18°C, 150 rpm, 4 mM IPTG), yielding 597.06 ± 21.32 µg/g dry cell weight (DCW).
• Achieved a 2.2-fold increase in astaxanthin production (1.3 mg/g DCW) by co-localizing terminal pathway enzymes.
• Demonstrated the synergistic effect of fermentation optimization and enzyme self-assembly for higher yields.

Conclusions:

• Data-driven process selection and spatial enzyme organization are effective strategies for improving carotenoid production.
• Engineered E. coli can be developed into highly efficient cell factories for astaxanthin.
• This study provides a framework for intensifying microbial biosynthesis of valuable compounds.