Feed-Grade Riboflavin Production

The process under analysis comprises two major sections: (1) Fermentation; and (2) Product Recovery and Purification.

Fermentation. Initially, the culture media used in the pre-fermentation and in the fed-batch fermentation are prepared by diluting the nutrients in water. The applied recombinant microorganism is propagated in an aerobic pre-fermentation step to obtain the proper inoculum concentration. When there is a sufficient mass of bacteria colony, the microorganism inoculum from the pre-fermentation step is fed into the fermenters. Fed-batch medium is continuously supplied to the fermenters, and the main fermentation is also carried out under aerobic process conditions. The pH control is made by addition of a solution of ammonia (NH3) and sulfuric acid, so as to keep the pH of the fermentation broth around 7. The fermentation is allowed to proceed for 48 hours, when the feeding is suspended and the fermentation is interrupted.

Product Recovery and Purification. The fermentation broth obtained in each main fermenter at the end of the fed-batch phase is fed to an agitated, jacketed tank where it is heated at about 60 °C for approximately 30 minutes for pasteurization. The pasteurized broth, rich in Riboflavin, is then fed to three decanter centrifuges operating in series for the recovery of a product with a purity of about 90 wt%. After each centrifugation step, the separated denser layer (richer in Riboflavin than in the previous step) is re-dissolved and forwarded to a subsequent centrifuge. The Riboflavin cake is treated with hot hydrochloric acid for further degradation of cells and cell constituents. The treated suspension is cooled and subsequently directed to a vacuum belt filter, where Riboflavin is separated and washed. The wet Riboflavin cake is conveyed to a rotary dryer where remaining water is removed from the Riboflavin and the dried product obtained, with a purity of 96 wt%, is finally packed.