Bio-Methionine Production from Raw Sugar

The process under analysis comprises four major sections: (1) Fermentation; (2) Clarification and Demineralization; (3) Pre-concentration, Crystallization and Filtration; and (4) Products Recovery.

Fermentation. Culture media used in the fermentation is prepared by mixing water, invert sugar (glucose and fructose), and ammonium thiosulfate solution (60 wt% in water) in the medium vessels. A microorganism is used to produce L-methionine through aerobic fermentation, which is divided in two phases: batch and fed-batch phases. During the first, the fermenters are filled with batch medium and fermentation occurs until glucose exhaustion, when the fed-batch phase is started by addition of the fed-batch medium until the end of the fermentation.

Clarification and demineralization. Culture broth is clarified by centrifugation and ultrafiltration. Next, the broth is demineralized in ion exchange resins to remove cations and anions.

Pre-concentration, crystallization, and filtration. L-methionine is concentrated in an evaporator prior to crystallization under vacuum by water evaporation. Then, precipitated methionine is sent to a vacuum filter, where it is separated from the crystallization mother liquor that still contains dissolved methionine.

Products recovery. Filtered L-methionine is directed to a dryer, where L-methionine powder with 99.5 wt% of dry matter (90 wt% of methionine) is obtained. Water evaporated is sent to a wash column and then used in methionine washing. Also, the crystallization mother liquor is acidified with hydrogen chloride, and then concentrated, resulting in the liquid L-methionine compound by-product, which presents 60 wt% of dry matter (22 wt% of methionine).