Location: Bioenergy ResearchTitle: Cellulosic butanol biofuel production from sweet sorghum bagasse (SSB): Impact of hot water pretreatment and solid loadings on fermentation employing Clostridium beijerinckii P260
Submitted to: BioEnergy Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/25/2016
Publication Date: 6/8/2016
Publication URL: http://handle.nal.usda.gov/10113/5732733
Citation: Qureshi, N., Liu, S., Hughes, S., Palmquist, D., Dien, B., Saha, B. 2016. Cellulosic butanol (ABE) biofuel production from sweet sorghum bagasse (SSB): Impact of hot water pretreatment and solid loadings on fermentation employing Clostridium beijerinckii P260. BioEnergy Research. 9(4):1167-1179. doi: 10.1007/s12155-016-9761-z.
Interpretive Summary: Butanol is a superior fuel than ethanol and packs 30% more energy. It can be blended with gasoline in any proportion, can be transported in existing pipelines, and burns cleaner (with less shoot). It can be produced from agricultural residues such as corn stover, wheat straw, and barley straw which are not as costly as corn or molasses. In the present studies butanol was produced from sweet sorghum bagasse (SSB) because it costs much less than corn thus resulting in the production of butanol more economically. However, SSB requires heat treatment using either water, or dilute acid followed by hydrolysis using enzymes to release sugars from SSB for fermentation to butanol. In these studies we used water to treat SSB for 2 reasons: i) it is environmentally friendly, and ii) it is not costly. Using sugars generated by hot water treatment technique, we were successful producing butanol from this feedstock. Production of butanol using this technology would benefit U.S. farming communities, biofuel and transportation industries, and United States public and will make us independent of foreign oil.
Technical Abstract: A novel butanol fermentation process was developed in which sweet sorghum bagasse (SSB) was pretreated using liquid hot water (LHW) pretreatment technique followed by enzymatic hydrolysis and butanol (acetone butanol ethanol; ABE) fermentation. A pretreatment temperature of 200 deg C resulted in the generation of a hydrolyzate that inhibited butanol fermentation. When SSB pretreatment temperature was decreased to 190 deg C (0 min holding time), the hydrolyzate was successfully fermented without inhibition and an ABE productivity of 0.51 gL-1h-1 was achieved which is comparable to the 0.49 gL-1h-1 observed in the control fermentation where glucose was used as a feedstock. These results are based on the use of 86 gL-1 SSB solid loadings in the pretreatment reactors. We were also able to increase SSB solid loadings from 120-200 gL-1 in the pretreatment step (190 deg C) followed by hydrolysis and butanol fermentation. As pretreatment solid loadings increased, ABE yield remained in the range of 0.38-0.46. In these studies, a maximum ABE concentration of 16.88 gL-1 was achieved. Using the LHW pretreatment technique, 88.40-96.00% of carbohydrate was released in the SSB hydrolyzate. The LHW pretreatment technique does not require chemical additions, is environmentally friendly, and the hydrolyzate can be used successfully for butanol fermentation.