Genome reduction improves octanoic acid production in scale down bioreactors

Area of Science:

• Biotechnology
• Metabolic Engineering
• Microbial Physiology

Background:

• Microbial bioreactors face challenges with heterogeneous conditions due to mixing limitations.
• Nutritional gradients in large-scale cultures can trigger wasteful stress responses, reducing bioprocess efficiency.
• Scale-up of bioprocesses carries significant risks due to unpredictable impacts of environmental heterogeneity.

Purpose of the Study:

• To engineer a metabolically optimized Escherichia coli strain (WG02) for enhanced octanoic acid production from glycerol.
• To evaluate the performance of WG02 compared to a standard E. coli strain (WG01) under various bioreactor conditions.
• To assess the impact of engineered metabolic cost reduction on bioprocess scale-up.

Main Methods:

• Engineered E. coli strain RM214 (WG02) by reducing genomic metabolic load.
• Compared WG02 and E. coli MG1655 (WG01) in batch-flask and fed-batch bioreactor cultivations.
• Utilized carbon-limited, nitrogen-limited, and scale-down (stirred tank + plug flow reactor) bioreactor systems.

Main Results:

• In carbon-limited fed-batch, WG02 increased biomass by over 22% with similar octanoic acid titres compared to WG01.
• Nitrogen-limited cultivation of WG02 yielded a 16% higher octanoic acid titre by reducing biomass accumulation.
• In a scale-down system, WG02 improved octanoic acid titre by nearly 18% while maintaining comparable biomass.

Conclusions:

• Metabolically optimized E. coli strains can mitigate the negative effects of intermittent stress in bioreactors.
• Reducing genomic metabolic cost in platform strains enhances bioprocess performance during scale-up.
• WG02 demonstrates improved robustness and productivity for octanoic acid synthesis in challenging bioreactor environments.