(216a) Biobutanol Production Using Clostridium Beijerinckii From Ultrafiltered Corn Fiber Hydrolysate and Recycled Spent Broth

In these studies, a mutant strain of Clostridium beijerinckii was used to produce butanol (acetone?butanol?ethanol, or ABE) from corn fiber in an immobilized fibrous-bed bioreactor. Inhibitors present in fermentation of renewable lignocelluloses requires complicated pretreatments which includes repeated adsorption and overliming of the hydrolysate. Thus, ultrafiltration, which is a cost-effective and environmentally benign process, was considered in the purification of the acid hydrolysate prior to fermentation. Sterilization of the medium was carried out using microfiltration to prevent degradation of sugars and formation of more products that may inhibit microbial growth. It has been demonstrated that the use of 80%(v/v) corn fiber hydrolysate as fermentation medium can produce ~3 to 4 g biobutanol per liter of fermentation broth with productivity of ~0.06 g/L-h. The highest titer of biobutanol was achieved within 72 hours of fermentation. The ratio of acetone-butanol-ethanol (ABE) mixture remained at 3:6:1 using the acid corn fiber hydrolysate, however, the concentration of acetic acid and butyric acid produced was more than two times higher than ABE concentration. Results showed that higher titer of biobutanol up to 16 g/L and productivity of ~0.11 g/L-h can be achieved when fermentation time was prolonged for ~6 days. Another significant result of the studies showed that reuse of fermentation broth was possible for the first recycle. Second recycle of spent broth produced very low biobutanol titer due to the accumulated inhibitors in the broth which cannot be reduced by ultrafiltration. Therefore, further purification of spent broth is needed to be able to reuse the broth in the next fermentation batch. It is recommended that further studies must be conducted for prolonged fermentation of corn fiber hydrolysate. The utilization of sugars in the corn fiber hydrolysate must be studied during the prolonged fermentation as well as the factors affecting fermentation process.