Rebalancing microbial carbon distribution for L-threonine maximization using a thermal switch system.

Area of Science:

• Metabolic Engineering
• Synthetic Biology
• Microbial Biotechnology

Background:

• Unbalanced microbial carbon distribution limits natural metabolite production.
• Efficient L-threonine maximization strategies are scarce.
• Current methods often focus on target pathways, neglecting central metabolism regulation.

Purpose of the Study:

• To develop a novel strategy for maximizing L-threonine production by controlling cellular carbon distribution.
• To engineer a dynamic regulatory system for improved cofactor supply and metabolite yield.
• To enhance the efficiency of L-threonine biosynthesis in Escherichia coli.

Main Methods:

• Designed a temperature-responsive thermal switch genetic circuit.
• Implemented a two-stage fermentation process (growth and production).
• Controlled heterologous expression of pyruvate carboxylase and oxaloacetate decarboxylation to rebalance carbon flux.

Main Results:

• Achieved an 111.78% molar yield of L-threonine from glucose using the initial thermal switch system.
• Further optimized the system to switch off the L-alanine synthesis pathway.
• Attained a record L-threonine yield of 124.03%, surpassing the theoretical maximum and previous reports.

Conclusions:

• The thermal switch system effectively rebalances carbon distribution for enhanced L-threonine production.
• This inducer-free genetic circuit offers a versatile platform for other biosynthetic pathways.
• The strategy significantly improves product conversion rates and shortens production cycles in microbial fermentation.