Cellulosic Butanol (ABE) Biofuel Production from Sweet Sorghum Bagasse (SSB): Impact of Hot Water Pretreatment and Solid Loadings on Fermentation Employing Clostridium beijerinckii P260
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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 °C resulted in the generation of a hydrolyzate that inhibited butanol fermentation. When SSB pretreatment temperature was decreased to 190 °C (0-min holding time), the hydrolyzate was successfully fermented without inhibition and an ABE productivity of 0.51 g L−1 h−1 was achieved which is comparable to the 0.49 g L−1 h−1 observed in the control fermentation where glucose was used as a feedstock. These results are based on the use of 86 g L−1 SSB solid loadings in the pretreatment reactors. We were also able to increase SSB solid loadings from 120 to 200 g L−1 in the pretreatment step (190 °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 g L−1 was achieved. Using the LHW pretreatment technique, 88.40–96.00 % of polymeric sugars (cellulose + hemicellulose) were released in the SSB hydrolyzate. The LHW pretreatment technique does not require chemical additions and is environmentally friendly, and the hydrolyzate can be used successfully for butanol fermentation.
KeywordsSweet sorghum bagasse (SSB) Liquid hot water (LWH) pretreatment Butanol fermentation Inhibitors ABE productivity ABE yield
N. Qureshi would like to thank Professor David Jones (Otago University, Dunedin, New Zealand) for his generous gift of Clostridium beijerinckii P260. NQ would also like to thank Gregory Kennedy (US Department of Agriculture, Agricultural Research Service, National Center for Agricultural Utilization Research, Peoria, IL, USA) for analyzing SSB hydrolyzate samples for sugar estimation.
Compliance with Ethical Standards
This work does not involve use of human subjects or animals.
Conflict of Interests
The authors do not have any conflict of interests.
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