Submitted to: Biomass and Bioenergy
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/5/2007
Publication Date: 2/1/2008
Citation: Qureshi, N., Saha, B.C., Cotta, M.A. 2008. Butanol production from wheat straw by simultaneous saccharification and fermentation using Clostridium beijerinckii: Part II - fed-batch fermentation. Biomass and Bioenergy. 32:176-183.
Interpretive Summary: Butanol is a superior fuel and chemical than ethanol. It also has higher energy content than ethanol and can be produced from agricultural crops and crop residues such as lignocellulosic materials. In a study, it has been identified that raw material cost influences butanol production price significantly. Hence, it was considered that use of economically available raw materials would make production of butanol economically attractive. For this reason, these studies were focused on production of butanol from wheat straw using a microbial culture known as Clostridium beijerinckii. In these studies, it has been demonstrated that butanol could be produced from wheat straw hydrolyzed to monomeric sugars using dilute acid and enzymes. Hydrolysis of wheat straw to sugars (glucose, xylose, mannose, arabinose, and galactose), their conversion to butanol, and butanol recovery were achieved in a single reactor (single step). In this process, hydrolysis efficiency and butanol productivity were improved. Successful production of butanol from lignocellulosic materials would benefit U.S. farmers and the U.S. public. Development of such an alternative fuel and chemical is essential since gas prices have been rising steadily.
Technical Abstract: In these studies, Clostridium beijerinckii P260 was used to produce butanol (acetone butanol ethanol, or ABE) from wheat straw (WS) hydrolyzate in a fed-batch reactor. It has been demonstrated that simultaneous hydrolysis of WS to achieve 100% hydrolysis to simple sugars (to the extent achievable under present conditions) and fermentation to butanol is possible. In addition to WS, the reactor was fed with a sugar solution containing glucose, xylose, arabinose, galactose, and mannose. The culture utilized all of the above sugars. It was noticed that near the end of fermentation (286-533 h), the culture had difficulties utilizing xylose. As a result of supplemental sugar feed to the reactor, ABE productivity was improved by 16% as compared to previous studies. In our previous experiment on simultaneous saccharification of WS and fermentation to butanol, a productivity of 0.31 gL**-1h**-1 was observed, while in the present studies a productivity of 0.36 gL**-1h**-1 was observed. It should be noted that a productivity of 0.77 gL**-1h**-1 was observed when the culture was highly active. The fed-batch fermentation was operated for 533 h. It should be noted that C. beijerinckii P260 can be used to produce butanol from WS in integrated fermentations.