Production of Itaconic Acid in a Continuous Fermentation Process

One of the more promising applications of bipolar membranes is the adjustment of the pH value of fermentation solutions to recover the organic acids from the spent medium. As an example the production of itaconic acid is described below.

Conventionally, itaconic acid is produced by a batch fermentation process. During fermentation the pH value shifts towards lower values due to the production of the acid. To avoid product inhibition the pH is maintained at a high level by addition of sodium or ammonium hydroxide which form soluble salts with the produced itaconic acid. At the end of the fermentation processes, the free acid is recovered from the spent medium by lowering the pH value by adding sulfuric acid. The adjustment of the pH values in the fermenter as well as in the spent medium is not only costly, but also creates salts mixed with the desired product and thus further purification steps are required. By applying bipolar membrane technology the production of salts can be eliminated and the itaconic fermentation can be carried out more ef ficiently in a continuous process, as illustrated in the production scheme depicted in Figure 7. The flow scheme shows a fermenter combined with an elec-trodialysis unit fitted with bipolar membranes. The fermenter is continuously fed with substrate and its constituents passed through an ulfiltration unit. The retained biomass is recycled to the reactor while the product containing filtrate is fed to the middle cell of a three-compartment electrodialyser repeating unit. In this cell the solution will be depleted of the ions. The cations, i.e. sodium or ammonium ions, permeate the cation exchange membrane and form, with the OH~ ions generated in the bipolar membrane, NaOH which is concentrated and then fed back into the bioreactor to adjust the pH value. The anions, i.e. the itaconate ions, permeate the anion exchange membrane and form, with protons generated at the bipolar membrane, the itaconic acid which is then concentrated and precipitated. Thus, the itaconic acid is produced in a continuous process without the addition of acids or bases, i.e. without the production of additional salts.

Solar Panel Basics

Solar Panel Basics

Global warming is a huge problem which will significantly affect every country in the world. Many people all over the world are trying to do whatever they can to help combat the effects of global warming. One of the ways that people can fight global warming is to reduce their dependence on non-renewable energy sources like oil and petroleum based products.

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