Pyruvic acid, also known as a-oxopropionic acid, has a structure of C H3CO CO O H, which is an important intermediate for the sugar metabolism of all biological cells and the mutual transformation of various substances in the body. Because the molecule contains activated ketone and carboxyl groups, it is widely used in various fields such as chemical, pharmaceutical, food, agriculture and environmental protection as a basic chemical raw material. It can be prepared by various methods such as chemical synthesis and biotechnology.
English synonym: 2-oxopropionic acid; acetyl formic acid; pyruvic acid; A-ketopropionic acid; acetamidinecarboxylic acid; PYRUVIC ACID; acetyl formate;
slight yellow liquid
Light yellow to yellow transparent liquid. Has an acetic acid smell. It has a sour taste. Natural products are found in mint and sucrose fermentation broth. The relative molecular mass is 88.06. The relative density is 1.2271. The temperature of 13.8 ° C.
Boiling point 165 ° C (decomposition)
106.5 ° C (13.332 × 103 Pa)
85.3 ° C (5.333 × 103 Pa)
70.8 ° C (2.666 × 103 Pa)
57.9 ° C (1.333 × 103 Pa)
45.8 ° C (0.667 × 103 Pa)
21.4 ° C (0.133 × 103 Pa)
The flash point is 82 °C. The refractive index is 1.4280. Miscible with water, ethanol, ether, etc.
The color darkens in the air. It is slowly polymerized during heating, and is highly reactive. It easily reacts with nitrides, aldehydes, halides, phosphides, etc., and participates in the biomimetic synthesis, metabolism, and alcohol fermentation of sugar metabolism, colloids, amino acids, and proteins. When applied, it is reduced to lactic acid in the muscle, oxidized again at rest and partially converted to glycogen. Pyruvic acid is a component of the human body. It is mainly involved in the metabolism of sugar and fat in the human body and is also one of the intermediate products of carbohydrate metabolism.
Pyruvic acid is a weakly acidic organic acid. It has two functional groups, carbonyl and carboxyl. It has the properties of carboxylic acid and ketone, and has the properties of α-keto acid. It is the simplest α-ketone. Acid (belongs to carbonyl acid). Pyruvic acid is a tricotonic acid produced in the body. It is the final product of the glycolytic pathway. It is reduced to lactic acid in the cytoplasm, or oxidized into mitochondria to form acetyl CoA, enters the tricarboxylic acid cycle, and is oxidized to carbon dioxide. And water, complete the aerobic oxidation energy supply process of glucose. Pyruvate can also convert the sugar, fat and amino acids in the body through the acetyl CoA and the tricarboxylic acid cycle. Therefore, pyruvic acid plays an important pivotal role in the metabolic linkage of the three major nutrients.
Studies have shown that pyruvate can inhibit the oxidation of oxygen free radicals in rats, and as a hydrogen peroxide scavenger, it has the effect of preventing free radical damage. It has been proven to protect against cardiac reperfusion injury and acute renal failure. The body is resistant to functional damage. Pyruvic acid acts as an antioxidant through two mechanisms:
First, as an α-keto acid, pyruvic acid can directly inhibit hydrogen peroxide by a non-enzymatic decarbonation reaction;
Second, the supplementation of pyruvic acid can enhance the citric acid cycle. After the increase of citric acid production, it inhibits the phosphofructokinase and enters the pentose phosphate bypass to produce reduced coenzyme II (NADPH), thereby indirectly increasing glutathione (GSH). The ability of the antioxidant system. Pyruvate also increases the ratio of coenzyme I/reduced coenzyme I (NAD+/NADH) to promote the tricarboxylic acid cycle reaction.
Tartaric acid dehydration and decarboxylation
The process is simple and easy: the mixture of tartaric acid and potassium hydrogen sulfate is distilled at 220 ° C, and the distillate is subjected to vacuum distillation to obtain pyruvic acid. The method is characterized in that after the heat transfer oil is added, the reaction is carried out in a uniform system, the reaction temperature is lowered, the degree of oxidation is reduced, the operability is greatly improved, and it is suitable for continuing to react to form a pyruvic acid series product. The disadvantage is that the yield of pyruvic acid is lower than that of the bottom, and it takes 5 g of potassium hydrogen sulfate to obtain 1 g of pyruvic acid. The disadvantage is that the cost is too high.
Lactic acid oxidation
Pyruvic acid is produced in one step by oxidative dehydrogenation using lactic acid as a raw material. However, it is very difficult to prepare pyruvic acid directly from lactic acid, and a suitable catalyst must be selected depending on the process. The catalysts which can be selected are iron phosphate, bismuth molybdate, silver, vanadium and the like. Compared with the oxidative decarboxylation method of the tartaric acid, the method has the advantages of low energy consumption, low pollution, high yield, and the like, and is suitable for industrial production. The disadvantages are costly.
A technique in which an enzyme or a microbial cell is used as a catalyst to convert certain intermediate metabolites of glucose or a tricarboxylic acid cycle to pyruvic acid under certain conditions, which is called an enzymatic method. The main process is to carry out small-scale microbial culture, collect the cells, directly transform or embed the immobilized enzyme with a carrier, and then convert to pyruvate. The enzyme catalytic method has small investment, low energy consumption and high conversion rate, but the substrate source is narrow and the cost is relatively high.
Genetic engineering technology
The use of genetic recombination technology to construct a genetically engineered strain that highly expresses glycolate oxidase, catalase, etc., for the production of pyruvic acid. These enzymes catalyze the reaction of lactic acid with oxygen to form pyruvic acid. The technique is to first recombine the glycolate oxidase gene and the catalase gene with a DNA vector to form a recombinant, and then transfer them to a host cell, respectively, to obtain genetically engineered yeast with high expression of two enzymes, according to 0.713 m ol / The LL-sodium lactate solution was added to 5 g of the heavy transformant per 100 ml, and a certain amount of penetrant was added thereto. At 5 atmospheres, oxygen was introduced at 70 psig of oxygen, and the mixture was stirred and transformed at 5 ° C for 4 hours, and the yield of pyruvic acid was 97.7%. The conversion rate of the substrate of the technology is high, but the technical difficulty is large.
In the process of microbial metabolism, the process of accumulating pyruvic acid using glucose is called microbial fermentation. Microbial fermentation has been studied for the production of pyruvic acid for 50 years. However, it is very difficult to breed pyruvate-producing strains. Although some microorganisms can accumulate pyruvic acid, their yield cannot meet the industrial requirements. The real breakthrough in the production of pyruvic acid by this method was that in 1988, researchers from Toray Industries, Ltd. of Japan, Miyata and Miyahara, selected a series of spheroid yeast strains with a pyruvic acid yield of more than 50 g/L to make microorganisms. The industrialization of pyruvic acid by fermentation is made possible. In 1992, Japan began to produce pyruvic acid by microbial fermentation. The output is 400 tons per year and the cost is about 2-3 million yuan per ton.
Compared with the chemical synthesis method and the enzyme conversion method, the microbial fermentation method has superior raw materials, low energy consumption, less pollution, low cost and superiority. However, the disadvantage of microbial fermentation is that the conversion rate is relatively low. This is because pyruvic acid is a key intermediate in the glycolytic pathway. In cells, pyruvate acts as an important intermediate metabolite to link the metabolic pathways of EM P and TCA. It is also associated with multiple branch metabolic pathways and can be converted into a variety of fermentation products that cannot be accumulated in the body. Therefore, it is necessary to cut or weaken its further metabolism in order to accumulate it in cells. That is to accelerate the conversion of glucose to pyruvate, reduce the flux to the TCA cycle, cut or weaken its branching metabolic pathway, promote secretion, reduce the re-use of pyruvic acid, and finally achieve a large accumulation of pyruvic acid. In order to achieve this, it is necessary to study the factors affecting the production of pyruvic acid by microbial fermentation.
The factors influencing the production of pyruvic acid by microbial fermentation include: strain selection, nutrient conditions, vitamin levels, oxygen supply mode, glucose concentration, etc. The most important factors are strain selection and nutritional conditions.