(470b) Two-Stage in Situ Gas Stripping for Enhanced Butanol Fermentation in a Fibrous Bed Bioreactor and Energy-Saving Product Recovery

Acetone-butanol-ethanol (ABE) fermentation with a hyper-butanol producing C. acetobutylicum JB200 was studied for its potential to produce a high titer of butanol that can be readily recovered with two-stage gas stripping. In batch fermentation without gas stripping, 80.0 g/L glucose was consumed by Clostridium acetobutylicum JB200 immobilized in a fibrous bed bioreactor, producing 7.9 g/L acetone, 16.2 g/L butanol and 1.4 g/L ethanol. When the two-stage gas stripping was incorporated into fed-batch fermentation, 49.2 g/Lacetone, 113.3 g/Lbutanol and 9.7 g/Lethanol were produced from 474.9 g/L glucose in six feeing cycles over 326 h, and butanol yield and productivity increased by 20% and 16.7%, respectively. The higher productivity was attributed to the reduced butanol concentration in the fermentation broth by gas stripping that alleviated butanol inhibition to cells, whereas the increased butanol yield could be attributed to the reduced acids accumulation as most acids produced in acidogenesis were reassimilated by cells for ABE production. Meanwhile, the recovered condensate containing 150.5 g/L butanol and 195.9 g/L ABE was collected from the first-stage gas stripping. Since butanol has the solubility of 7.7% (w/w) in water, the condensate obtained has two phases due to the butanol concentration in the condensate far exceeding its solubility in water. Consequently, after phase separation, the organic phase contained ~610 g/L butanol and ~660 g/L ABE and the aqueous phase contained ~80 g/L butanol and ~120 g/L ABE, which was then subjected to second-stage gas stripping. The mixture of the organic phase and condensate of the second-stage gas stripping contained ~430 g/L butanol and ~560 g/L ABE, which could be purified at much less energy consumption. Compared to conventional ABE fermentation, the fed-batch fermentation with two-stage gas stripping has the potential to reduce energy consumption and water usage in n-butanol production from glucose.