Pyruvate formation and suppression in recombinant Bacillus megaterium cultivation

Area of Science:

• Microbiology
• Biotechnology
• Metabolic Engineering

Background:

• Bacillus megaterium is a robust bacterium used in industrial fermentations.
• High-yield pyruvate production is a key goal for biotechnological applications.
• Understanding metabolic regulation in B. megaterium is crucial for optimizing fermentation processes.

Purpose of the Study:

• To engineer a recombinant Bacillus megaterium strain for enhanced pyruvate secretion.
• To investigate the relationship between growth rate, pyruvate formation, and byproduct generation.
• To optimize fermentation conditions for high biomass and pyruvate yields.

Main Methods:

• Recombinant DNA technology was used to modify B. megaterium.
• Controlled fermentation experiments were conducted using exponential feeding strategies.
• Pyruvate, biomass, acetate, and succinate concentrations were quantified.
• Metabolic flux analysis was inferred from observed production patterns.

Main Results:

• The engineered B. megaterium secreted up to 27.8 g/L of pyruvate at growth rates above 0.15 h(-1).
• Cultivation below 0.15 h(-1) minimized pyruvate, acetate, and succinate production.
• Exponential feeding achieved high final biomass concentrations of up to 80 g/L.
• Molar yields for pyruvate formation reached 0.79 mol/mol.

Conclusions:

• Pyruvate overproduction in B. megaterium is linked to a metabolic imbalance between glycolysis and the tricarboxylic acid cycle under glucose excess.
• High pyruvate concentrations inhibit growth, potentially via the phosphotransferase system glucose import mechanism.
• Optimized cultivation strategies can control pyruvate formation and maximize biomass yield in B. megaterium.