Editing Team:TU Darmstadt/Project/Bio/Monomeres/Haconsaeure

Biotechnological production of itaconic acid in Escherichia coli

 

The compilation of our toolbox requires beside the implemented polyalcohols (xylitol and ethyleneglycol) a molecule containing two carboxygroups for esterifications with these polyalcohols.  Furthermore it is important that one compartment of the polymer contains a crosslinking group which composes bonds with other strings under specific conditions. A molecule that complies with our requirements is the dicarbonacid itaconic acid. We, the iGEM team TU Darmstadt 2015; want to accomplish an alternative way of itaconic acid fabrication in Escherichia coli as host.

Itaconic acid is already used as a Co-monomer for the synthesis of polyacrylates and vulcanized rubber as well as a basic module for biologically degradable Polymers that are for example used in packaging industry. The conventional exploitation of itaconic acid is achieved by chemical synthesis or takes place in Aspergillus terreus where amounts of 80g/L are provided.(1) An important disadvantage of the recent production is the high costs of approximately US$4/kg. (2) Along with further biotechnologically relevant chemicals, itaconic acid was listed by the U.S Department of Energy as one of the twelve platform chemicals with especially biotechnologically production potential. These wide areas of application as well as the existing opportunities for improvement are the reasons for us to focus partly on itaconic acid.(3)

Itaconic acid has several chemically plus physico-chemical characteristics that we are going to use for us. The carboxyl groups allow itaconic acid to be esterified with hydroxyl-groups of several sugaralcohols, for example ethylene glycol, and thereby compose long chains of heteropolymers. The property to act as a Co-monomer with different other components has the consequence that itaconic acid is discussed as possible substitute for methacrylic acid that is utilized to date by petrochemical industry.(4)

Another remarkable feature itaconic acid contains are the three different protonation states with pKa-values of 3.83 and 5.55 ((5);) that are typically for a dicarboxylic acid. Thereby the reaction responsiveness can be varied by adjusting the pH-value.

To permute the idea of biotechnological production of itaconic acid in a different host than Aspergillus terreus, the required enzyme needs to be implemented in the host of our choice. Therefore we benefit from the already existing TCA-cycle intermediates metabolized by E.coli and tie in with the synthesis of cis-aconitate.
The in E.coli metabolism newly implemented Protein, cis-aconitate-decarboxylase coded by cadA, forms cis-aconitate to itaconic acid. 

                                                                               <img src="filemanager/source/Itaconic acid pathway.jpg" alt="Itaconic acid pathway" width="392" height="439" />

                                                                                                                                         <img src="bildname.jpg" alt="Itaconic acid pathway">

    1.            Huang X, Chen M, Lu X, Li Y, Li X, Li JJ. Direct production of itaconic acid from liquefied corn starch by genetically engineered Aspergillus terreus. Microb Cell Fact. 2014;13:108.

    2.            Willke T, Vorlop KD. Biotechnological production of itaconic acid. Appl Microbiol Biotechnol. 2001;56(3-4):289-95.

    3.            Okabe M, Lies D, Kanamasa S, Park EY. Biotechnological production of itaconic acid and its biosynthesis in Aspergillus terreus. Appl Microbiol Biotechnol. 2009;84(4):597-606.

    4.            Huang X, Lu X, Li Y, Li X, Li JJ. Improving itaconic acid production through genetic engineering of an industrial Aspergillus terreus strain. Microb Cell Fact. 2014;13:119.

    5.            Klement T, Buchs J. Itaconic acid--a biotechnological process in change. Bioresour Technol. 2013;135:422-31.