[γ-Polyglutamic acid production in Corynebacterium glutamicum using sugar by one-step fermentation]

Area of Science:

• Biotechnology
• Microbial Engineering
• Biopolymer Production

Background:

• Gamma-polyglutamic acid (γ-PGA) is a versatile biopolymer with applications in food, cosmetics, and medicine.
• Current γ-PGA production relies on glutamic acid-dependent strains, increasing manufacturing costs.
• Developing sugar-based γ-PGA production is crucial for economic viability.

Purpose of the Study:

• To establish a de novo γ-PGA production method using sugars as a substrate.
• To engineer Corynebacterium glutamicum for efficient γ-PGA synthesis.
• To optimize production conditions and evaluate yield and molecular weight.

Main Methods:

• Cloned the γ-polyglutamate synthase gene cluster (pgsBCA) from Bacillus subtilis.
• Expressed pgsBCA in Corynebacterium glutamicum under inducible and constitutive promoters.
• Optimized induction conditions (time, IPTG concentration) and tested in different strains (ATCC 13032, F343).

Main Results:

• Inducible expression of pgsBCA in C. glutamicum ATCC 13032 yielded 1.43 g/L γ-PGA from glucose without glutamic acid.
• Optimized conditions increased γ-PGA titer to 1.98 g/L.
• Expression in C. glutamicum F343 achieved 10.23 g/L (shake flask) and 20.08 g/L (fermentor) γ-PGA.
• γ-PGA from the recombinant strain F343 exhibited a 34.77% higher weight-average molecular weight.

Conclusions:

• Successfully established a de novo γ-PGA production from sugars in engineered Corynebacterium glutamicum.
• Demonstrated the feasibility of high-titer γ-PGA production without glutamic acid supplementation.
• The developed method offers a cost-effective and scalable approach for γ-PGA manufacturing with potential for enhanced properties.