Adipic acid is the most industrially important dicarboxylic acid as it is a key monomer in the synthesis of nylon. Adipic acid is obtained via a chemical process that relies on petrochemical precursors and releases large quantities of greenhouse gases[2]. Enoate reductase from Clostridium acetobutylicum (CaER), an oxygen-sensitive reductase, was demonstrated to have in vivo enzyme activity of converting cis,cis-muconic acid to adipic acid under microaerobic condition. Engineered Escherichia coli strains were constructed to express the whole pathway and accumulated 5.8 ± 0.9 mg/L adipic acid from simple carbon sources[3]. Yeasts and A. niger were found to tolerate substantially higher concentrations of adipic acid than bacteria, and were less affected by the undissociated form of adipic acid than bacteria. The yeast exhibiting the highest tolerance to adipic acid was Candida viswanathii, showing a reduction in maximum specific growth rate of no more than 10-15% at the highest concentration of adipic acid tested and the tolerance was not dependent on the dissociation state of the adipic acid[4]. Moreover, the increase in adipic acid concentration was significantly and indirectly correlated with the severity of the deficit in socialization and communication skills in children with an ASD (autism spectrum disorders ) [5].
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