The Main Raw Material For The Synthesis Of PLA (polylactic Acid).

Lactic acid is the main raw material in the synthesis of polylactic acid.

Lactic acid is mainly produced by fermentation and chemical synthesis, and the fermentation method uses natural raw materials, which is the main method of lactic acid production, with a large market and strong competitiveness.

Types and properties of lactic acid
Lactic acid, also known as 2-hydroxypropionic acid, can be divided into D-lactic acid (dextralative), L-lactic acid (left-handed) and D, L-lactic acid (racemic) with its different optical rotations. L-lactic acid can be completely metabolized and absorbed by the human body without any toxic side effects, while D-lactic acid can not only be metabolized and absorbed by the human body, but will lead to an increase in blood uric acidity, causing metabolic disorders in the human body. The World Health Organization (WHO) clearly stipulates that the daily intake of D-lactic acid by the human body shall not exceed 100mg/kg, therefore, from a safety point of view, it has become a trend for L-lactic acid to replace the existing D-lactic acid.

Synthesis of lactic acid
(1) Raw materials for the synthesis of lactic acid The main raw materials for the production of lactic acid are starch substances, such as corn, rice, beans, etc. Different raw materials for the production of lactic acid have different strains. If molasses and starch water are dissolved as raw materials, Dersonella is mostly used; If milk or whey is used as raw materials, Lactobacillus Bulgaria and Lactobacillus casei are mostly used. The production of L-lactic acid is made by lactic acid bacteria or Rhizopus. At present, the production of L-lactic acid at home and abroad is widely used in Rhizopus oryzae.

(2) Fermentation and synthesis of lactic acid The fermentation and production of lactic acid mainly uses starch as raw materials, and glucose, molasses, etc. can also be used as raw materials. The traditional fermentation process of producing lactic acid by calcium salt method is as follows: firstly, the starch is saccharified, and after the selected strains are accessed, calcium carbonate is added to neutralize the lactic acid produced, and the pH value is adjusted at 5.0~5.5, so that the strains are fermented at a temperature suitable for the production of acid for 3~6 days, and the fermentation broth of calcium crude lactate is generated. The key to the fermentation method is the selection of strains, which are mainly used for fermentation to produce lactic acid, cells and Rhizopus.