Production of fumaric acid by fermentation

Fermentative fumaric acid production from renewable resources may become competitive with petrochemical production. This will require very efficient processes. So far, using Rhizopus strains, the best fermentations reported have achieved a fumaric acid titer of 126 g/L with a productivity of 1.38 g L−1 h−1 and a yield on glucose of 0.97 g/g. This requires pH control, aeration, and carbonate/CO2 supply. Limitations of the used strains are their pH tolerance, morphology, accessibility for genetic engineering, and partly, versatility to alternative carbon sources. Understanding of the mechanism and energetics of fumaric acid export by Rhizopus strains will be a success factor for metabolic engineering of other hosts for fumaric acid production. So far, metabolic engineering has been described for Escherichia coli and Saccharomyces cerevisiae.