دانلود رایگان مقاله تنفس آندیک از سودوموناس KT2440 در بیوراکتور

ABSTRACT

Anodic batch production of para-hydroxybenzoic acid (pHBA) from citric acid with a genetically modified Pseudomonas putida KT2440 strain was studied in a bio-electrochemical system (BES) based on a standard lab-scale stirred-tank bioreactor at fully controlled anaerobic reaction conditions. Electron transfer to the anode was mediated by addition of K3Fe(CN)6 to the medium. Effects of varying anode surface areas (graphite rod, felt and brush), power input (stirrer speed) and mediator concentrations were investigated. The obligate aerobic P. putida grew anaerobically with mediated anodic respiration and pHBA production was observed. Anodic respiration was best applying the graphite rod electrode which showed a maximal current density of 12.5 mA cm−2. This is the highest measured for non-porous electrodes in BES until now. Increasing the power input to 2.93W L−1 (700 rpm) and online control of the redox potential EMedium at 225 mV (vs. Ag/AgCl) in the medium by controlled addition of mediator resulted in a maximal pHBA yield of 9.91 mmolCpHBA molC−1 citrate which exceeds pHBA yields in the aerobic batch process by 69 % (5.87 mmolCpHBA molC−1 citrate).

4. Conclusion

A fully controlled stirred-tank bioreactor can be reversibly transformed into a bio-electrochemical system. Increasing mass transfer by increasing the stirrer speed (volumetric power input) canenable faster anodic electro-fermentations.Control ofthe redox potential in the medium can be used to improve stable anodic respiration. Combining both approaches enhanced anodic respiration, product formation and current densities significantly.Proper control of the redox potential in the medium by feeding of mediator and increased power input to minimize mass transfer limitations, combined with optimised working electrode materials and engineered microorganisms will lead to improvements of electro-fermentations. More than any previous reactor, the stirred tank-based bio-electrochemical system described here will enable reliable reaction engineering analysis and support comparability between results.