Performance of metabolic pathway biomimetic reactors. I. Influence of hydrodynamics

Understanding and controlling the micro-environment in cell culture systems is essential to conduct intrinsic metabolic pathway studies. These are with either intact cellular or biomimetic systems. Novel reactor systems, as developed in our laboratory, couple membrane and electrode technologies that isolate key mechanistic steps. The biosynthesis of lactate from pyruvate was selected as a model system to demonstrate their capabilities. A key feature is the in-situ regeneration of the coenzyme NADH. Cyclic voltammetry was used to investigate the mechanisms present. Porous graphite electrodes utilize an immobilized enzyme system (lipoamide dehydrogenase) and methyl viologen as a mediator) encapsulated by a cation exchange membrane (Nafion 124). The free flowing fluid contains the pyruvate/lactate (and co-products), the enzyme lactate dehydrogenase and the NADH/NAD+ system. Lactate yields up to 70% were obtained when the reactor system was operated in a recirculation mode for 24 hours, as compared to only 50% in 200 hours when operated in a simple batch mode. Regimes where mass transfer or kinetics control process synthesis were identified by flow variations