PLA is a polyester produced by fermentation under controlled conditions of a carbohydrate source like corn starch or sugarcane. Its building blocks can either be lactic acid or lactide monomers. They will later be polymerized into PLA.
Initially, corn goes through wet milling. Here’s were the starch gets separated. The starch is then mixed with acid or enzymes and heated. This process “breaks” starch into dextrose (D-glucose), or corn sugar. Finally, fermentation of glucose produces L-Lactic acid, which will be the basic constituent of PLA.
Two methods for manufacturing PLA plastic from lactic acid are applied. The first one uses lactide as an intermediate state, which results in greater molecular weight. The second method consists in the direct polymerization of lactic acid.