Using enzymatic hydrolyzate as new nitrogen source for L-tryptophan fermentation by E.coli

Area of Science:

• Biotechnology
• Microbial Fermentation
• Biochemical Engineering

Background:

• Waste bacterial cells pose disposal challenges.
• Sustainable methods for utilizing biomass are crucial for industrial processes.
• L-tryptophan is an essential amino acid with significant market demand.

Purpose of the Study:

• To develop an efficient method for hydrolyzing waste bacterial cells.
• To evaluate the efficacy of bacterial cell hydrolyzate as an organic nitrogen source for L-tryptophan fermentation.
• To optimize conditions for maximizing free amino acid content in the hydrolyzate.

Main Methods:

• Pre-treatment and enzymatic hydrolysis of waste bacterial cells using trypsin and compound protease.
• Optimization of hydrolysis conditions (pH, temperature, time, enzyme/substrate ratio) via orthogonal tests.
• Fermentation of L-tryptophan using the prepared hydrolyzate as a nitrogen source.

Main Results:

• Optimized hydrolysis achieved a free amino acid content of 500.61 mg/g.
• The bacterial cell hydrolyzate, when used as a nitrogen source (1:1 with yeast extract), supported L-tryptophan production of 53.87 g/L.
• Maximum biomass reached 53.45 g/L during fermentation.

Conclusions:

• Waste bacterial cells can be effectively utilized as a sustainable organic nitrogen source.
• The developed hydrolysis method enhances nutrient availability for microbial fermentation.
• This approach offers a viable strategy for waste valorization and L-tryptophan production.