Downstream processing of biobased succinic acid (1)

Unlike ethanol, which you can just distill away from other components, you cannot do that with succinic acid! Downstream processing is key steps to commercialize biobased succinic acid production. The broth of succinic acid (SA) fermentation has a lower SA concentration (~60 g/L) with the side products such as acetic acid, meleic acid, formic and lactic acid etc. It is a major factor involved in industrial scale production using fermentation due to the cost (60%) involved in downstream processing to concentrate and purify the products.

There are techniques needed for pure SA production and efficient recovery process. SA fermentation usually proceeds best at an approximately neutral pH (6.0-7.0), but acid products will eventually lower the pH,therefore,the pH of the broth needs to be rained and maintained by addition of base; The added basic compounds generally react with the acid to form salts rather than the desired free acid product itself. The traditional succinic acid recovery method is based on precipitation and crystallization technology, acidification by ion-exchange resins and crystallization process:
–Removal of insoluble materials such as dead cells

–Concentrate the fermentation broth
–Acidification
–Crystallization and filtration
–Purification of the acidified product by ion-exchange resins

Approach I: Ca-Based SA Separation: Precipitation and Washing
(Datta et al. US Patent, 5, 168,055)

• Key process-related problems
–Separation of dilute product streams and the related cost of recovery
–Elimination of the salt waste from current purification process
–The reduction of inhibition to the product of the fermentation itself
–Separation of other acidic by-products such acetic acid, formic acid, lactic acid, citric acid,etc.

•Product related problems
- one mole of product ends up one mole of gypsum, which is a by-product with little value
- Odor and color contamination

- Comsumption of CaO, CaOH, and H2SO4, which are not regenerated within the process