L-Lysine-HCl Production from Raw Sugar

The process under analysis comprises three major sections: (1) Fermentation; (2) Product Recovery; and (3) Product concentration, Drying and Packaging.

Fermentation. The culture media used in fermentation is prepared by mixing process water, invert sugar and nutrients. The fermentation is performed in fed-batch mode and under aerobic conditions. At the batch phase, the microorganism seed is fed into the fermenters, which were previously filled with the fermentation batch medium. After glucose exhaustion, the batch phase is finished and the fed-batch phase is started, during which, glucose and nutrients are continuously supplied until the desired L-lysine concentration is achieved. At the end of the fermentation, the broth is sent to a buffer tank to provide a continuous flow in the further process steps.

Product recovery. The fermentation broth is sent to an ultrafiltration system for the removal of cell debris and other suspended solids. Subsequently, the liquor from ultrafiltration is fed to ion exchange columns, where L-lysine is selectively adsorbed. The L-lysine adsorbed is eluted from the ion exchange resins by washing with an aqueous ammonia solution.

Product concentration, drying and packaging. The L-lysine eluate from ion exchange columns is mixed with mother liquor from product filtration and concentrated by evaporation. The concentrated lysine solution is acidified with hydrochloric acid, and free L-lysine is converted to L-lysine HCl. Subsequently, the L-lysine HCl solution is sent to the crystallizer, and lysine salt is filtered. The mother liquor is recycled to the evaporator and the wet cake is conveyed to dryers. Final dry L-lysine-HCl (98.5 wt%) is obtained and sent to packaging line before being stored in bags.