Butanol and Ethanol Production from D-glucose in a Fixed-Film Fluidized Bed Clostridium acetobutylicum Biological Reactor
Sislo, Erin Elizabeth
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The development of biologically created fuel is proving to be not only an environmentally conscious research path but also a commercially viable means of production due to abundant lignocellulosic biomasses and carbohydrates. Fermentation is an environmentally conscious and economical process that can be used biologically, through bacterium or fungi driven digestion, to create high-value fuels such as butanol and ethanol. Clostridium acetobutylicum is able to digest D-glucose and favor the production of butanol at a high rate under anaerobic conditions, while yeast is able to digest D-glucose with the simultaneous production of ethanol under anaerobic conditions. By creating a fixed film fluidized bed biological reactor with either of these microorganisms, a biologically created fuel can be produced through fermentation on a continuous basis. A fixed film fluidized bed biological reactor was chosen as the continuous reactor for this experimental testing because it allows the reaction, or in this case digestion, to occur over a length of the reactor, rather than only in a particular area, allowing for high efficiency. Based on a theoretical model previously developed for an aerobic system, an anaerobic microorganism was tested to determine if a fixed film could be formed during fluidization in a reactor column. It was determined that the anaerobic bacteria, Clostridium acetobutylicum, was unable to form this structure under the high flow rate conditions needed for particle fluidization; however, yeast cells were able to form this biological layer under the described conditions in the fluidized reactor. The theoretical model, developed previously, was then tested and verified on the anaerobic fungi system by forming a fixed film on the particles present in the fluidized bed reactor. During the digestion of D-glucose, biomass accumulation of the fungi occurred due to the growth of the fungi in a nutrient-rich environment. A manual scouring method was used and demonstrated to be effective; but, the method was not time efficient due to the constant growth of the fungi under conditions of the consistent nutrient flow.