Method for preparing L-methionine by using acetylated saponification solution

Abstract

The invention relates to a preparation method of L-methionine aiming at the field of the chemical industry. The preparation method comprises the following steps of: adding acid into an acetylated saponification solution which is used as a production raw material to adjust the pH, cooling and then performing crystallization to obtain D,L-acetylmethionine crystals; and adding the obtained D,L-acetylmethionine into amino invertase to perform resolution reaction so as to obtain L-methionine, and recycling remainders. According to the method, links for refining D,L-methionine are reduced, the saponification solution for producing the D,L-methionine is directly used for performing acetylation reaction, and the yield is up to 99%; and besides, neutralization and separation steps for production of the D,L-methionine are reduced, the L-methionine obtained by performing enzymolysis on recrystallized D,L-acetylmethionine at an enzymolysis speed which is higher than that of the conventional method is better in crystal form and whiteness, the purity is more than 99.5%, and the total yield of the L-methionine is improved to 70%. The preparation method is a comprehensive cycle process which is reasonable in design and reduces the production cost.

Description

technical field [0001] The invention aims at the field of chemical industry and relates to a method for preparing L-methionine, in particular to a method for jointly preparing L-methionine by using D,L-methionine to produce saponification liquid. Background technique [0002] L-methionine, as a common reagent in biochemical research and a routine nutritional supplement, is also widely used in the adjuvant treatment of pneumonia, liver cirrhosis and fatty liver. At present, a variety of preparation methods of L-methionine have been reported, but most of the preparation methods are still in the laboratory stage, and only a few methods can be used in industrial production later. Among these methods, the commonly used means are enzymatic resolution or enzymatic cleavage, such as in the US patents of US6114163 and US6524837, enzymatic resolution of D, L-acetyl-methionine or enzymatic cleavage of D, L-methylthioethyl Hydantoin. [0003] In the prior art, the aminotransferase rou...

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Problems solved by technology

[0004] However, in the above-mentioned documents, the raw materials D and L-methionine for preparing L-methionine are all purified D, L-methionine commercial products, and their purity is above 98%, which will inevitably lead to an increase in the cost of L-methionine. However, there is no report on the direct use of the saponified liquid obtained from the hydrolysis of D,L-methylthioethylhydantoin (hydantoin) in the process of producing D,L-methionine to directly produce D,L-acetylmethionine.

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