Cis-cis muconic acid (MA) utilized as a raw material for new functional resins, pharmaceuticals and agrichemicals is an unsaturated dicarboxylic acid with six carbon atoms. MA was revealed to be easily converted to adipic acid, a valuable commodity chemical for bio-plastics including nylon 6-6 and polyurethane and polyethylene terephthalate (PET). For development of MA high-yielding recombinant Escherichia coli cells, three additional genes from various sources (i.e., both aroZ gene encoding DHS dehydratase from and aroY gene encoding PCA decarboxylase from K. pneumonia, and catA gene encoding catechol 1,2-dioxygenase from A. calcoaceticus) were introduced into aromatic amino acids auxotropic mutants by use of plasmid expression vectors with various strong promoters. As a first step to enhanced production of MA by the newly-developed E. coli cells, induction strategy was set up at 5L bioreactor level through determination of inducer kind & amount, induction time and inducing medium composition. Especially, intensive studies were conducted to develop an efficient induction method for overcoming catabolite repression phenomenon caused by high level of residual glucose. Medium optimization was also carried out in order to find optimal compositions of the growth and production medium, respectively. For this purpose, statistical methods were adopted, such as one factor at a time (OAFT), full factorial design (FFD), steepest ascent methods (SAM) followed by response surface methods (RSM). In addition, fermentation conditions such as agitation speed, sparger type, dissolved oxygen level and pH-control were also investigated using the 5L stirred tank bioreactors. Fermentation results from the batch and fed-batch bioreactor operations performed with the recombinant E. coli cells will be presented in this paper as well.

Cis-cis muconic acid production by the recombinant Escherichia coli cells  in batch and fed-batch bioreactor fermentations

247th National Meeting (2014)

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