[Construction and optimization of engineered Bacillus subtilis for surfactin production]

Area of Science:

• Microbiology
• Biotechnology
• Biochemistry

Background:

• Surfactin, a potent biosurfactant, offers diverse applications in oil recovery, agriculture, pharmaceuticals, food, and cosmetics.
• Industrial production of surfactin is contingent upon enhancing its yield through microbial engineering and optimized culture conditions.

Purpose of the Study:

• To investigate the influence of the fatty acid synthesis pathway on surfactin production.
• To engineer Bacillus subtilis for increased surfactin titers.
• To optimize fermentation parameters for maximal surfactin yield.

Main Methods:

• Genetic engineering of Bacillus subtilis THBS-2 and THBS-8 by overexpressing key genes in the fatty acid synthesis pathway.
• Optimization of culture conditions, including the addition of isopropyl-beta-D-thiogalactopyranoside (IPTG) and amino acids.
• Development of a two-stage fermentation strategy involving specific timings and concentrations of IPTG, leucine, and condensed culture medium.

Main Results:

• Engineered Bacillus subtilis strains (THBS-2 and THBS-8) demonstrated significantly enhanced surfactin production.
• A two-stage culture method was established, with optimal addition times and concentrations for IPTG and leucine.
• Surfactin titer reached 24 g/L in shake flasks and 34 g/L in a 30-L fermentor using the optimized strategy.

Conclusions:

• Overexpression of fatty acid synthesis genes and optimized fermentation conditions are effective strategies for high-yield surfactin production.
• The developed two-stage culture method significantly enhances surfactin titers in Bacillus subtilis.
• This research provides a foundation for the large-scale industrial production and widespread application of surfactin.