Monosodium glutamate is a salt formed by glutamate ions and sodium ions, and is the main component of MSG.
In 1908, Japanese chemistry professor Kikunae Ikeda extracted a white chemical substance from kelp, which was tested to be sodium glutamate. He found that this was the secret to the delicious taste of kelp soup, and applied for a patent and named it " Ajinomoto" became a best-selling product.
After Japan’s Ajinomoto was introduced to China, it aroused the interest of a chemical engineer named Wu Yunchu. He bought a bottle to study it. Later, he independently invented a method for producing sodium glutamate. , called MSG. In wheat bran (gluten), the content of glutamic acid can reach 40%. He first used 34% hydrochloric acid to hydrolyze the gluten under pressure to obtain a black hydrolyzate. After decolorization with activated carbon and vacuum concentration, white crystals were obtained. of glutamic acid. Then react glutamic acid with sodium hydroxide, concentrate, and dry to obtain sodium glutamate. He was the first person in the world to use hydrolysis to produce MSG.
It is very uneconomical to produce MSG through hydrolysis, because this method consumes a lot of grain. It takes at least 40 tons of wheat to produce 1 ton of MSG. Moreover, when extracting sodium glutamate, a lot of unpleasant-tasting gases are released, the hydrochloric acid used is also easy to corrode machinery and equipment, and a lot of harmful sewage is produced. Therefore, MSG companies have to continue research work in order to use better methods to produce better products.
In 1956, Japan's Kyowa Hakko Co., Ltd. announced that they had found this "little craftsman", which was Brevibacterium. The fermentation production of monosodium glutamate was born. Xiehe scientists prepared a culture solution with sugar, water and urea, and then used high-temperature steam sterilization to kill all the miscellaneous bacteria. Then they inoculated the cultivated pure Brevibacterium into the most favorable environment to allow They reproduce. Thanks to the efforts of "little craftsmen", most of the sugar and urea are converted into glutamic acid, and finally, they are neutralized into sodium salt.
Industrial production began around 1957, and now most sodium glutamate is produced using this method.
Preparation method
1. Fermentation raw materials: starch, saccharification liquid, waste molasses and synthetic acetic acid are used as carbon sources, and neutralized ammonia, urea, etc. are used as nitrogen sources. In addition, a certain amount of inorganic salts such as potassium phosphate, magnesium sulfate, and iron sulfate, biotin, and thiamine (vitamin B2) are also added, and an appropriate amount of penicillin and surfactant must also be added.
2. Processing and fermentation: Put the sterilized raw materials into a large vat, and inoculate the cultured bacteria in it. Various strains of bacteria have been found for producing glutamic acid, but bacteria of the genera Micrococcus glutamicus and Brevibacterium are often used. Add about 5% of the pre-culture solution to the culture solution, and feed 1/2 to 1/4 of the raw material capacity of sterile air every minute on average. Stir and culture while feeding. The acidity is maintained at PH7-8. The strain that produces glutamic acid is a type of bacteria with special physiological properties. If the environmental conditions cannot meet the requirements, the fermentation process of glutamic acid will not proceed.
3. Sterilization: Generally, after 40 hours of culture at 30-32°C, the bacteria are filtered to remove the glutamic acid solution.
4. Concentration, crystallization, and separation: Concentrate the glutamic acid solution to obtain glutamic acid crystals.
5. Neutralization and refining: Neutralize and refine with sodium hydroxide or sodium carbonate to produce sodium glutamate. The yield of glutamic acid is 30 to 50% of the sugar used.
However, when domestic MSG factories extract glutamic acid from fermentation broth, they are generally limited by the existing equipment and processes. They do not separate the bacteria first, but directly extract glutamic acid from the bacteria containing bacteria and proteins. When extracting glutamic acid from fermentation broth, since the bacterial cells present in the fermentation broth are not conducive to the separation of glutamic acid crystals, it is difficult to improve the yield, control the quality, and deal with a large amount of high-concentration wastewater generated during the production process. to completely resolve the shortcomings.