Submitted to: Applied Biochemistry and Biotechnology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/4/2016
Publication Date: 1/14/2016
Publication URL: http://handle.nal.usda.gov/10113/62617
Citation: Nghiem, N.P., Senske, G.E., Kim, T.H. 2016. Pretreatment of corn stover by low moisture anhydrous ammonia (LMMA) in a pilot-scale reactor and bioconversion to fuel ethanol and industrial chemicals. Applied Biochemistry and Biotechnology. 179(1):111-125. Interpretive Summary: Cellulosic biomass such as corn stover is a potential renewable feedstock for production of fuels and chemicals by biological processes. Bioprocessing of biomass requires reacting it with a chemical such as acid, base or organic solvent to open up the rigid structure to allow efficient production of sugars by commercial enzyme products. This first step is called “pretreatment”. Another issue related to biomass fermentation is transportation and long-term storage. In this investigation, we studied the effect of pretreatment of corn stover by gaseous ammonia in a pilot-scale reactor on its long-term storage. It was found that gaseous ammonia treatment preserved the carbohydrates and did not negatively affect the subsequent production of sugars by commercial enzyme products. We also studied the fermentation of the pretreated corn stover to ethanol and two other chemicals, namely butyric acid and succinic acid, which have many industrial applications.
Technical Abstract: Corn stover (CS) adjusted to 50%, 66% and 70% moisture was pretreated by the low moisture anhydrous ammonia (LMAA) process in a pilot-scale ammoniation reactor. After ammoniation, the 70% moisture CS was treated at 90 degree C and 100 degree C whereas the others were treated at 90 degree C only. The 70% moisture pretreated CS then was subjected to a storage study under non-sterile conditions for 3 months. It was found that storage time did not have significant effects on the compositions of the pretreated materials and their hydrolysis by commercial enzymes. The 70% moisture CS treated at 90 degree C was used for preparation of a mix sugar hydrolysate (MSH) using combination of cellulase and xylanase. The MSH was used to prepare a corn mash at 9.5 wt% solid then subjected to ethanol fermentation by Escherichia coli KO11. The 66% moisture CS treated at 90 degree C was hydrolyzed with xylanase to make a xylose-rich hydrolysate (XRH), which was subsequently used for butyric acid fermentation by Clostridium tyrobutyricum. The resultant cellulose-enriched residue was hydrolyzed with cellulase to make a glucose-rich hydrolysate (GRH), which was subsequently used for succinic acid fermentation by Escherichia coli AFP184.