Pathway analysis for production of L-leucine by Brevibacterium flavum TK0303
黄色短杆菌TK0303的L-亮氨酸生物合成途径分析

Brevibacterium flavum is used for the production of a number of amino acids in the biotechnology industry. The yield of producing a metabolite is ultimately limited by the ability of the central metabolism and the desired biosynthesis pathway. Pathway analysis is a very useful tool for metabolic engineering, which can be applied to increase the yield of a metabolite or channeling a metabolite into desired pathways. It does not require any kinetic parameters and only uses the Stoichiometric equations. Pathway analysis for production of L-leucine by Brevibacterium flavum TK0303 at steady state was conducted in this paper. Theoretical yield and flux distribution for optimal pathway were determined.It is also concluded that pyruvate and acetyl-coenzyme A are the key nodes of the L-leucine biosynthesis pathway by analyzing the flux distributions of different modes. According to the pathway analysis, the production of L-leucine is expected to be raised by strengthening the flux of the key nodes (pyruvate and acetyl-coenzyme A) through changing the environmental factors. Because the flux of TCA cycle in Brevibacterium flavum TK0303 is weak, the production of L-leucine must be provided enough amido by adding glutamic acid to the fermentation medium. NH_4Ac is both a carbon source and a nitrogen source, which could be helpful to the production of L-leucine. The effects of glutamic acid and NH_4Ac on the production of L-leucine were further studied. The production of L-leucine increased 56% by adding glutamic acid. By improving the concentration of NH_4Ac, the biosynthesis of L-leucine was greatly strengthened too. The results indicate that the flux of L-leucine can be largely increased by changing the chemical regulatory factors such as NH_4Ac and glutamic acid and the modes established by pathway analysis prove to be efficient to describe the metabolic network of L-leucine production by Brevibacterium flavum TK0303.