Abstract:

Methionine is widely used in many fields such as feed, food, pharmaceutical and biotechnology, and has an
increasing market demand. Compared with chemical synthesis, the biological production of methionine has many advantages
especially in sustainable production and environmental protection. The biological methods used for methionine production
include microbial fermentation and enzymatic treatment. Researchers have been trying to describe the biosynthetic pathway
of methionine and breed high methionine-producing strains. However, no bacteria are now used in industrial production of
methionine because of the complex biosynthesis pathway of this amino acid and the affinity with other intracellular reaction
systems. In-depth study of methionine biosynthesis pathway, expansion of methionine exporting system and optimization
of fermentation conditions are effective to increase the yield of methionine produced by the existing strains. The stateof-
the-art technology of enzymatic hydrolysis for the production of methionine, combining genetic engineering with
enzyme immobilization, has great application potential. This article summarizes the latest advances in the biotechnologies
for methionine production in China and abroad with emphasis on microbial fermentation, enzymatic treatment and their
combination. According to the characteristics of methionine production by microbial fermentation, existing problems and
corresponding suggestions with respect to the removal of allosteric inhibition, the application of composite sulfur source
and the stability of key enzymes are put forward. The combination of enzymatic treatment and microbial fermentation
is recommended to be used for the production of methionine from preferably hydrolyzed plant proteins, achieving the
advantages of low cost, low pollution, high yield and high purity.

Key words: methionine, biotechnology, microbial fermentation, enzymatic processing, isomer resoultion, enzymatic hydrolysis