Lactic acid - Preparation

Fermentation
Fermentation of sugar is the main way of ferrous lactate bacteria, adjust the pH value of about 5, for about 50 or 60dm; C Fermentation three to five days to give the crude acid. Fermentation of raw materials generally corn, rice, sweet potato starch material, alfalfa, cellulose and the like as raw material, the lactic acid fermentation stage to lactic acid production lot, but the acid does not have much higher quality, mainly Rhizopus and other strains of Lactobacillus. The fermentation of different strains of different ways, can be divided into the same type of fermentation and shaped fermentation, the actual presence of microorganisms as other physiological activities, may not be simply a certain kind of fermentation pathway. Sodium lactate the same type of fermentation and shaped fermentation.
Synthesis
Lactonitrile law: Lactonitrile method is to acetaldehyde and hydrogen cyanide cold milk continuously fed to the reactor to generate a nitrile (or directly with the milk as raw material nitrile), with a pump into the milk nitrile hydrolysis reactor, into sulfuric acid and water, the milk nitrilase crude lactic acid. And then give it away crude lactic acid esterification reactor, adding ethanol esterification, distillation, concentration, lactic acid decomposition was fine. American Sterling Chemical Company and Japan Musashino Chemical companies are adopting this synthesis of lactic acid.
Acrylonitrile law: acrylonitrile and acrylonitrile method is hydrolyzed in sulfuric acid fed to the reactor, and then hydrolysis reactor anyone to esterification reaction with methanol; then after separation of the hydrogen sulfate, the crude ester distillation column , the bottom was fine ester; then refined into a second distillation column ester, thermal decomposition, bottom too thin lactic acid, concentrated by vacuum to obtain the product.
Propionic acid method: method propionic acid as raw materials, through chlorination, hydrolysis of the crude lactic acid powder; re-esterification, distillation, hydrolysis products. This method is more expensive raw materials, only a few companies such as Japan's road contest manufacturers to adopt. Reaction is as follows:
 CH3CH2COOH Cl2 one → CH3CHClCOOH NaOH-→ CH3CH (OH) COOH NaCl
Enzymatic method
Chlorine acid enzymatic conversion: the use of the purified L-2-halo acid dehalogenase and DL-2-halo acid dehalogenase were acting on the substrate L-2-chloro-propionic acid and DL-2-chloro- acid, L-lactic acid obtained bittern off or D-lactic acid. L-2-halo acid dehalogenase catalyzed L-2-chloropropionic acid, and DL-2-halo acid dehalogenase catalyzed both L-2-chloropropionic acid, but also the catalytic L-2-chloropropyl generate the corresponding optically active acid, catalytic conversion simultaneous configuration. Enzymatic conversion of pyruvate: highest activity of lactate dehydrogenase from the chaos DSM20196 Lactobacillus cells obtained in D-lactic acid dehydrogenase, a non-optically active pyruvate as substrate D-lactic acid can be obtained.