Enhanced production of cis-cis muconic acid through medium optimization and bioprocess development using recombinant Corynebacterium glutamicum cells

Cis-cis muconic acid (MA), an unsaturated dicarboxylic acid with six carbon atoms was reported to be easily converted to adipic acid, a valuable commodity chemical for bio-plastics including nylon 6-6 and polyurethane and polyethylene terephthalate (PET). As a first step to mass production of MA, medium optimization was carried out in order to find optimal compositions of both growth- and production-medium. For this purpose, efficient statistical methods were adopted, such as full factorial design (FFD), steepest ascent methods (SAM) followed by response surface methods (RSM). In bioreactor fermentations, C/N ratio of the production medium was observed to have significant influences on the MA productivity of the high-yielding recombinant cells of C. glutamicum. Notably, Status of the inoculated cells (i.e., inoculum age and inoculum amount) transferred to the final production fermentor were revealed to have profound effects on the biosynthetic capability of the producing cells. In addition, physiochemical fermentation conditions such as dissolved oxygen level and pH-control were intensively investigated using 5L stirred tank bioreactors. As a result, approximately 10 fold increase in MA production level was obtained in the 5L bioreactor cultures performed under the optimized conditions, as compared to the shake-flask fermentations.