Immobilization of filamentous fungi: A new frontier in the production of organic acids

Some fungal metabolites, either primary or secondary, as well as enzymes and other biotransformation products of fungal origin play a strategic role in many technologies and in particular in food processing. Among these, organic acids appear to be of major interest. Citric acid is already produced at more than 600x10(3) Tons/year and the market demand for other acids such as gluconic, lactic and malic is continuously increasing. This review is mainly devoted to the most recent advances in the production of organic acids from immobilized fungal cell systems. Fumaric acid production by immobilized Rhizopus arrhizus is reported as a case study. In fact, the fermentative production of this acid, which has long been abandoned for economic reasons and substituted by direct chemical synthesis, might greatly benefit from the use of an immobilized-cell based technology.