Reaction engineering studies of butanol fermentation with Clostridium acetobutylicum strains in stirred-tank reactors

Michael Schmidt, doctoral thesis Technische Universität München, 2013

Butanol used as biofuel features improved physical  properties and higher energy density compared to ethanol. The strictly anaerobic microorganism Clostridium acetobutylicum is able to produce butanol with renewable resources as feedstock. A scalable reference batch process was established in stirred-tank bioreactors to compare different recombinant Clostridium acetobutylicum strains at defined technical process conditions. The reference batch process was scaled down to 48 parallel stirred-tank bioreactors on a milliliter scale which were successfully operated keeping anaerobic conditions in an aerobic environment. It was shown that the volumetric butanol batch productivity was increased by a factor of nearly 5 compared to the wildtype strain making use of recombinant strains overexpressing key enzymes of the central carbon metabolism. A selectivity of more than 50 % (mol butanol / mol glucose) was achieved with these strains.

Publications

• Janzen N, Schmidt M, Krause C, Weuster-Botz D (2015): Evaluation of fluorimetric pH-sensors for bioprocess monitoring at low pH. Bioproc Biosys Eng 38: 1685-1692.
• Schmidt M, Weuster-Botz D (2012): Reaction engineering studies of acetone-butanol-ethanol fermentation with Clostridium acetobutylicum. Biotechnol J 7: 656-661.
• Lehmann D, Hönicke D, Ehrenreich A, Schmidt M, Weuster-Botz D, Bahl H, Lütke-Eversloh T (2012): Modifying the product pattern of Clostridium acetobutylicum: Physiological effects of disrupting the acetate and acetone formation pathways. Appl Microbiol Biotechnol 94: 743-754.