High solid fed-batch butanol fermentation with simultaneous product recovery: Part II - process integration.

Authors: Qureshi, Nasib; Saha, Badal; Klasson, K Thomas; Liu, Siqing

Submitted to: Biotechnology Progress
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/13/2018
Publication Date: 4/25/2018
Citation: Qureshi, N., Saha, B.C., Klasson, K.T., Liu, S. 2018. High solid fed-batch butanol fermentation with simultaneous product recovery: Part II - process integration. Biotechnology Progress. 34(4):967-972. https://doi.org/10.1002/btpr.2643
DOI: https://doi.org/10.1002/btpr.2643

Interpretive Summary: Butanol, a superior biofuel than ethanol, was produced from Sweet Sorghum Bagasse (SSB). The cost of butanol production is affected by feedstock price and process technology including fermentation and product recovery. In these studies we used a special type of reactor (fed-batch reactor) to produce butanol. The reactor was fed with a concentrated SSB hydrolyzate and the product (butanol) was recovered simultaneously by applying vacuum. Feeding the reactor with concentrated hydrolyzate would reduce the size of the reactor thus decreasing the capital and operational costs. At the same time, use of fed-batch reactor and simultaneous recovery would combine production and recovery in one unit. This would reduce the production cost further. These technologies are expected to reduce the cost of production of this biofuel significantly. Commercial production of this biofuel using SSB and the developed process technology would benefit the transportation industry and the consumers.

Technical Abstract: In these studies liquid hot water (LHW) pretreated and enzymatically hydrolyzed Sweet Sorghum Bagasse (SSB) hydrolyzates were fermented in a fed-batch reactor. As reported in the preceding paper, the culture was not able to ferment the hydrolyzate I in a batch process due to presence of high level of toxic chemicals, in particular acetic acid released from SSB during the hydrolytic process. To be able to ferment the hydrolyzate I obtained from 250 gL-1 SSB hydrolysis, a fed-batch reactor was devised. The reactor was started with the hydrolyzate II and when good cell growth and vigorous fermentation were observed, the hydrolyzate I was slowly fed to the reactor. In this manner the culture was able to ferment all the sugars present in both the hydrolyzates to acetone butanol ethanol (ABE). In a control batch reactor in which ABE was produced from glucose, ABE productivity and yield of 0.42 gL-1h-1 and 0.36 were obtained, respectively. In the fed-batch reactor fed with SSB hydrolyzates these productivity and yield values were 0.44 gL-1h-1 and 0.45, respectively. ABE yield in the integrated system was high due to utilization of acetic acid to convert to ABE. In summary we were able to utilize both the hydrolyzates obtained from LHW pretreated and enzymatically hydrolyzed SSB (250 gL-1) and convert them to ABE. Complete fermentation was possible due to simultaneous recovery of ABE by vacuum.