(440f) High Titer Butanol Production Using a Mutant Clostridium Beijerinckii Achieved by Adaptation in Fibrous Bed Bioreactor

As an important industrial chemical and a potential fuel, butanol has attracted more and more interest in recent years. Biological production of butanol is believed as a promising process because it can use renewable biomass as feedstock and is thus environmentally friendly. However, biobutanol production is not economic due to its low yield, productivity and titer. Among these three parameters, titer is the most difficult one to be improved due to the high cytotoxicity nature of butanol. To improve the butanol titer, butanol fermentations were conducted in a fibrous bed bioreactor (FBB)-connected fermentor system using an asporogenous mutant of Clostridium beijerinckii. Culture medium and process conditions were optimized to facilitate the butanol production. During the optimization, cells immobilized in FBB were used as seeds for each subsequent batch of fermentation and thus these cells were intermittently challenged with butanol produced by themselves. After several fermentation batches' adaptation, a mutant strain was isolated from the FBB. Compared with the original strain, the mutant showed higher butanol tolerance and reduced autolysis during the stationary phase. At the same time, for the mutant, the fermentation conditions needed to realize the metabolic shift from acidogenesis to solventogenesis were different from that of its parent strain. Therefore, fermentation conditions were optimized to maximize the butanol production potential of the mutant and finally high titer butanol production was achieved. The mutant strain makes the biobutanol production more economic and the strain improvement strategy used in this study may give illumination to other similar bioproduct researches