Effect of mechanical disruption on the effectiveness of three reactors used for dilute acid pretreatment of corn stover Part 1: chemical and physical substrate analysis

Biotechnology for Biofuels

David K Johnson²  Michael E Himmel²  Melvin P Tucker²  Seong H Kim³  Sunkyu Park¹  Christopher M Lee³  Kabindra Kafle³  Erik M Kuhn²  Rui Katahira²  Peter N Ciesielski²  Bryon S Donohoe²  Xiaowen Chen²  Wei Wang² 

[1]Department of Forest Biomaterials, North Carolina State University, Raleigh NC 27695, USA

[2]National Renewable Energy Laboratory, 15013 Denver West Parkway, Golden, CO 80401, USA

[3]Department of Chemical Engineering and Materials Research Institute, Pennsylvania State University, University Park, PA 16802, USA

关键词: digestibility;    substrate accessibility;    cellulose properties;    biomass;    dilute acid pretreatment;    Reactor;   

Others  :  792748
DOI  :  10.1186/1754-6834-7-57

 received in 2013-11-27, accepted in 2014-03-17,  发布年份 2014

【 摘 要 】

Background

There is considerable interest in the conversion of lignocellulosic biomass to liquid fuels to provide substitutes for fossil fuels. Pretreatments, conducted to reduce biomass recalcitrance, usually remove at least some of the hemicellulose and/or lignin in cell walls. The hypothesis that led to this research was that reactor type could have a profound effect on the properties of pretreated materials and impact subsequent cellulose hydrolysis.

Results

Corn stover was dilute-acid pretreated using commercially relevant reactor types (ZipperClave^® (ZC), Steam Gun (SG) and Horizontal Screw (HS)) under the same nominal conditions. Samples produced in the SG and HS achieved much higher cellulose digestibilities (88% and 95%, respectively), compared to the ZC sample (68%). Characterization, by chemical, physical, spectroscopic and electron microscopy methods, was used to gain an understanding of the effects causing the digestibility differences. Chemical differences were small; however, particle size differences appeared significant. Sum-frequency generation vibrational spectra indicated larger inter-fibrillar spacing or randomization of cellulose microfibrils in the HS sample. Simons’ staining indicated increased cellulose accessibility for the SG and HS samples. Electron microscopy showed that the SG and HS samples were more porous and fibrillated because of mechanical grinding and explosive depressurization occurring with these two reactors. These structural changes most likely permitted increased cellulose accessibility to enzymes, enhancing saccharification.

Conclusions

Dilute-acid pretreatment of corn stover using three different reactors under the same nominal conditions gave samples with very different digestibilities, although chemical differences in the pretreated substrates were small. The results of the physical and chemical analyses of the samples indicate that the explosive depressurization and mechanical grinding with these reactors increased enzyme accessibility. Pretreatment reactors using physical force to disrupt cell walls increase the effectiveness of the pretreatment process.

【 授权许可】

   
2014 Wang et al.; licensee BioMed Central Ltd.

【 图 表 】

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