Pretreatment of corn stover by low-liquid ammonia recycle percolation process |
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Authors: | Tae Hyun Kim Yoon Y Lee Changshin Sunwoo Jun Seok Kim |
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Institution: | (1) Department of Chemical Engineering, Auburn University, 36849 Auburn, AL |
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Abstract: | A pretreatment method using aqueous ammonia was investigated with the intent of minimizing the liquid throughput. This process
uses a flow-through packed column reactor (or percolation reactor). In comparison to the ammonia recycle percolation (ARP)
process developed previously in our laboratory, this process significantly reduces the liquid throughput to one reactor void
volume in packed bed (2.0–4.7 mL of liquid/g of corn stover) and, thus, is termed low-liquid ARP (LLARP). In addition to attaining
short residence time and reduced energy input, this process achieves 59–70% of lignin removal and 48–57% of xylan retention.
With optimum operation of the LLARP to corn stover, enzymatic digestibilities of 95, 90 and 86% were achieved with 60, 15,
and 7.5 filter paper units/g of glucan, respectively. In the simultaneous saccharification and fermentation test of the LLARP
samples using Saccharomyces cerevisiae (NREL-D5A), an ethanol yield of 84% of the theoretical maximum was achieved with 6% (w/v) glucan loading. In the simultaneous saccharification
and cofermentation (SSCF) test using recombinant Escherichia coli (KO11), both the glucan and xylan in the solid were effectively utilized, giving an overall ethanol yield of 109% of the
theoretical maximum based on glucan, a clear indication that the xylan content was converted into ethanol. The xylooligomers
existing in the LLARP effluent were not effectively hydrolyzed by cellulase enzyme, achieving only 60% of digestibility. SSCF
of the treated corn stover was severely hampered when the substrate was supplemented with the LLARP effluent, giving only
56% the overall yield of ethanol. The effluent appears to significantly inhibit cellulase and microbial activities. |
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Keywords: | Corn stover pretreatment aqueous ammonia bioenergy simultaneous saccharification and cofermentation |
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