Tuesday, May 3, 2011
The utilization of hemicellulose and cellulose components of plant biomass for the production of liquid fuel would be a process economically very attractive. The major sugars obtained after hydrolysis are glucose, xylose and arabinose. From all three sugars the fungus Ustilago maydis is able to produce itaconic acid (ITA). ITA, an unsaturated dicarboxylic acid, is a key building block which subsequently can be converted into a number of high-value bio-based chemicals and also to liquid fuel. The currently favored biotechnological production process involves Aspergillus terreus by which ITA is formed obviously from the tricarbonic acid intermediate cis-aconitate by the cis-aconitate decarboxylase. Little is known about regulatory principles and other metabolic details of the ITA production by this fungus.
U. maydis is a candidate for an alternative producer of ITA from pretreated biomass. This basidiomycetous fungus, that exhibits free-living yeast-like nonpathogenic and filamentous pathogenic forms, produces ITA from glucose and xylose also as a dual substrate. Glucose was the preferred substrate in the glucose/xylose mixture. The xylose uptake occurred when the glucose concentration was low, but the ITA formation was continuous and started when the nitrogen was exhausted. The total amount of ITA which had been formed was influenced by the ratio of glucose and xylose.