Medium optimization for ε-poly-L-lysine production by Streptomyces diastatochromogenes using response surface...

Area of Science:

• Biotechnology and Industrial Microbiology
• Biochemical Engineering
• Food Science and Technology

Background:

• Poly-ε-L-lysine (ε-PL) is a natural antimicrobial agent derived from L-lysine, recognized for its preservative qualities and diverse applications.
• Efficient production of ε-PL is crucial for its industrial viability as a food-grade antimicrobial preservative.

Purpose of the Study:

• To optimize the fermentation medium for enhanced production of ε-PL by Streptomyces diastatochromogenes 6#-7.
• To identify key factors influencing ε-PL yield and determine optimal concentrations for improved fermentation efficiency.

Main Methods:

• Utilized Plackett-Burman design to identify critical medium components affecting ε-PL production.
• Employed Response Surface Methodology (RSM), specifically the Box-Behnken experiment, for optimizing concentrations of glucose, yeast extract, and ammonium sulfate.
• Validated optimized conditions through shake-flask and 5 L jar-fermenter cultivations.

Main Results:

• Glucose, yeast extract, and (NH4)2SO4 were identified as the most significant factors influencing ε-PL production.
• Optimal concentrations determined were 60 g/L glucose, 7.5 g/L yeast extract, and 7.5 g/L (NH4)2SO4.
• ε-PL yield increased by 43.1% in shake-flask fermentation (0.948 g/L) and 56.4% in a 5 L jar-fermenter (25.5 g/L) compared to initial conditions.
• Fermentation time was reduced from 174 to 120 hours.

Conclusions:

• Medium optimization via RSM is a highly effective strategy for significantly increasing ε-PL yield in microbial fermentation.
• The optimized process offers economic benefits through improved yield, reduced by-products, and lower manufacturing costs.
• This approach is transferable to other microbial fermentations across pharmaceutical, food, agricultural, and energy sectors.