Water reuse in the L-lysine fermentation process

Area of Science:

• Biotechnology
• Industrial Microbiology
• Biochemical Engineering

Background:

• Commercial L-lysine production relies on fermentation, generating substantial liquid waste.
• Waste streams, primarily broth effluent from cation exchange chromatography, pose environmental and economic challenges.

Purpose of the Study:

• To investigate the feasibility of recycling L-lysine fermentation broth effluent to minimize waste.
• To assess the impact of effluent recycling on microbial growth and L-lysine production using Corynebacterium glutamicum.

Main Methods:

• Lab-scale fermentation experiments using Corynebacterium glutamicum ATCC 21253.
• Recycling broth effluent at varying ratios (75% in defined medium, 50% in complex medium with beet molasses).
• Monitoring cell mass, L-lysine concentration, and cation exchange column performance.

Main Results:

• A 75% effluent recycle ratio in defined medium sustained cell mass and L-lysine production over three batches.
• In complex medium, a 50% recycle ratio resulted in 8% lower L-lysine but 8% higher cell mass.
• Recycling effluent also allowed for the reuse of ammonium as a nitrogen source.
• A 17% decrease in cation exchange column capacity was observed with recycled complex medium effluent due to competing cations.

Conclusions:

• Recycling L-lysine fermentation broth effluent is a viable strategy for waste reduction and resource recovery.
• The recycle strategy can be maintained without compromising L-lysine production in defined media.
• Challenges exist in cation exchange efficiency when using recycled complex media effluent, necessitating further optimization.