Enhanced L-methionine production by genetically engineered Escherichia coli through fermentation optimization

Area of Science:

• Biotechnology
• Microbial Engineering
• Metabolic Engineering

Background:

• Microbial fermentation offers a sustainable route for L-methionine (L-Met) production from renewable resources.
• Genetic engineering of Escherichia coli (E. coli) MET-3 aims to enhance L-Met biosynthesis.
• Optimization of fermentation processes is crucial for efficient L-Met production.

Purpose of the Study:

• To improve L-methionine (L-Met) production by optimizing medium composition and fermentation conditions for genetically engineered E. coli MET-3.
• To identify key medium components and fermentation parameters affecting L-Met biosynthesis.
• To achieve higher L-Met titer, yield, and productivity through statistical optimization.

Main Methods:

• Utilized Plackett-Burman (PB) design to identify significant medium components (glucose, yeast extract, KH2PO4, MgSO4.7H2O).
• Employed Box-Behnken design (BBD) to determine optimal concentrations of key medium components.
• Optimized fermentation conditions including agitation rate, pH, and induction temperature in a 5-L fermentor.
• Conducted fed-batch fermentation with the modified medium and optimized parameters.

Main Results:

• PB design identified glucose, yeast extract, KH2PO4, and MgSO4.7H2O as significant factors.
• BBD optimization increased L-Met titer to 3.04 g/L from <2.0 g/L.
• Optimized fermentation conditions (300 rpm, pH 7.0, 28°C) further enhanced L-Met production.
• Fed-batch fermentation achieved a final L-Met titer of 12.80 g/L, a 38.53% increase.
• Yield and productivity were significantly improved to 0.13 mol/mol and 0.261 g/L/h, respectively.

Conclusions:

• Statistical optimization of medium composition and fermentation conditions is effective for enhancing L-Met production in engineered E. coli.
• The optimized fed-batch fermentation process resulted in substantial improvements in L-Met titer, yield, and productivity.
• These findings provide a valuable reference for further strain development and fermentation control in L-Met biosynthesis.