Enhancing the Efficiency of Bioreactors

Abstract

The objective of this dissertation research was to evaluate new methods to improve the efficiency of traditional bioreactors. CuSe nanoparticles were synthesized in batch reactors using the anaerobic bacteria, C. pasteurianum with the addition of an electron shuttle. In order to improve collection methods, C. pasteurianum was immobilized in 2% alginate beads and used to synthesize Pd nanoparticles in a continuous batch bioreactor. The immobilized C. pasteurianum had a comparable reduction of the Pd2+ ions to the control cultures and showed similar physical and catalytic characteristics to those formed in suspended cultures. The catalytic activity of the Pd Nanoparticles was evaluated using azo dye degradation. C. pasteurianum also efficiently reduced high concentrations of Mo6+. Various characterization techniques were used to confirm the formation of crystalline metallic Mo nanoparticles. It also was determined that the Nanoparticles acted as an effective catalyst for the degradation of MeO and were comparable to Pd Nanoparticles. For continuous flow reactors, spherical beads were typically used for immobilization due to greater surface area to volume ratios; the rate of diffusion by the substrate will be limited by the radius of the sphere. The use of water-soluble dopants was evaluated for use in alginate beads to increase the porosity. The advantage of water-soluble dopants was a significant decrease in the startup period and an increase in the ethanol yield. The ethanol production via threads was compared to beads. Synthesized threads were on average 1 mm in diameter. Threads showed similar ethanol yields between vertical and horizontal flow reactors. The beads showed a decrease in the ethanol yield when the reactor was operated in the horizontal flow direction. To further decrease the size of the immobilization, electrospinning was evaluated. Electrospinning produced micron sized threads. The immobilized cell reactors were able to obtain a maximum ethanol yield of 94.3%. The reactor was able to maintain a high ethanol yield of >90% from day 4 through day 14. Overall, this dissertation provides several methods by which productivity, yield, and efficiency of traditional batch-based bioreactors can be improved.