Alanine is one of the 20 basic amino acids constituting protein, an excellent transport tool for nitrogen in blood, and an effective glycogenic amino acid. D-alanine is contained in large organic tissues as a cell wall peptide wall sugar or peptide antibiotic. Experiments have shown that D-alanine is also abundant in adult dog urine and microorganisms. The content of D-alanine in the ethanolic extract of Lactobacillus Campylobacter is as high as 79%, and that in Lactobacillus helveticus is 59.2%. Exogenous D-alanine is carried into human tissues with the bloodstream.
Pharmaceutical applications of alanine
D-alanine is the raw material for the production of vitamin B, and it has analgesic effect itself, and the medicinal demand is 2.6 t. In some countries, D-alanine is also used as a drug to prevent facial flushing.
Recent studies have also found that D-alanine can ectopic expression of amino acid oxidase (DAAO) in tumor cytoplasm, preventing lipid oxidative damage in vivo and removing cytotoxicity. D-alanine can also inhibit the carcinogen dimethylnitrosamine (DMNA) with an inhibitory effect of 72.4. D-alanine with primary amine group can competitively replace secondary amine with nitrite to generate VAN Slyke reaction, which is decomposed into nitrogen gas and organic acid, thus inhibiting the generation of DMNA. Therefore, it has been suggested that D-alanine can be used as a new cancer gene therapy.
1. Food additives
D-alanine is mainly used for flavor enhancers and seasonings to increase the flavoring effect of chemical seasonings, improve the taste of artificial sweeteners, and improve the sourness of organic acids. In addition, D-alanine itself has its own characteristics and can be used in functional edible sweeteners. D-alanine is a strong sweet taste with a taste value of 4, which is the sweetest among amino acids. And D-alanine is an important raw material for the synthesis of dipeptide sweetener alitame (2.2.4.4-tea-methylthietanylamine). Ali Tian has good quality sweetness, pure taste, no peculiar smell and unpleasant aftertaste. Moreover, as a dipeptide, alitame only partially participates in the body's metabolism, and its maximum heat production is 1.4 keal/g, which is equivalent to 0.02% of the equivalent sweetness of sucrose, which is in line with people's current pursuit of low-calorie food.
2. Cosmetics
D-alanine has antibacterial effect, and is the main component of natural moisturizing factor (NMF), which plays an important role in maintaining moisture in the stratum corneum.
The preparation method of alanine
Due to the physiological activity and more and more extensive application of D-alanine, its preparation has aroused great interest. There are three general amino acid preparation methods: hydrolysis extraction, microbial fermentation, and chemical synthesis. Among them, the hydrolysis extraction method generally obtains L-amino acids, and is not suitable for the preparation of D-amino acids. At present, there are two other methods for the preparation of D-alanine, microbial fermentation and chemical synthesis.
1. Microbial fermentation
D-alanine can be produced by D-cycloserine resistant mutants of Saccharomyces brevis. However, the product concentration is low, the production cycle is long, the equipment investment is large, there are side reactions, and the separation is more complicated. And because of the activity of racemic alanine, the optical purity of the product D-alanine is relatively low.
2. Chemical synthesis
There are two kinds of chemical synthesis methods of D-alanine, one is to directly obtain D-alanine by asymmetric synthesis, and the other is to obtain the mixture of DL-alanine by chemical synthesis, and then use Various optical resolution methods were used to obtain D-alanine.
In a word, to establish the industrial production method of D-propanoic acid, the following principles must be considered: the starting materials are easy to obtain, the optical purity of the product is high, and the production capacity is large. Under these principles, enzymatic separation of chemically synthesized DL-alanine and its derivatives is more feasible in the industrial production of D-alanine, but it is necessary to establish the preparation of D-alanine. There are still many factors to consider in the process. The enzymes required for the reaction and catalysis are one important factor. The maintenance of enzyme activity and the recycling of enzymes are problems that need to be solved in the production process. With the development of science and technology, the combination of good testing technology and DNA recombination technology will make the nitrogen-acylase catalyst have strict stereoselectivity and high biological activity.
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