The impacts of deacetylation prior to dilute acid pretreatment on the bioethanol process

Biotechnology for Biofuels

Xiaowen Chen¹  Joseph Shekiro¹  Mary Ann Franden¹  Wei Wang²  Min Zhang¹  Erik Kuhn¹  David K Johnson²  Melvin P Tucker¹ 

[1] National Bioenergy Center, National Renewable Energy Lab, 1617 Cole Blvd, Golden, CO 80127, USA

[2] Biosciences Center, National Renewable Energy Lab, 1617 Cole Blvd, Golden, CO 80127, USA

关键词: Deacetylation;    Fermentation;    Enzymatic Hydrolysis;    Pretreatment;    Bioethanol;   

Others  :  798350
DOI  :  10.1186/1754-6834-5-8

 received in 2012-01-06, accepted in 2012-02-27,  发布年份 2012

【 摘 要 】

Background

Dilute acid pretreatment is a promising pretreatment technology for the biochemical production of ethanol from lignocellulosic biomass. During dilute acid pretreatment, xylan depolymerizes to form soluble xylose monomers and oligomers. Because the xylan found in nature is highly acetylated, the formation of xylose monomers requires two steps: 1) cleavage of the xylosidic bonds, and 2) cleavage of covalently bonded acetyl ester groups.

Results

In this study, we show that the latter may be the rate limiting step for xylose monomer formation. Furthermore, acetyl groups are also found to be a cause of biomass recalcitrance and hydrolyzate toxicity. While the removal of acetyl groups from native corn stover by alkaline de-esterification prior to pretreatment improves overall process yields, the exact impact is highly dependent on the corn stover variety in use. Xylose monomer yields in pretreatment generally increases by greater than 10%. Compared to pretreated corn stover controls, the deacetylated corn stover feedstock is approximately 20% more digestible after pretreatment. Finally, by lowering hydrolyzate toxicity, xylose utilization and ethanol yields are further improved during fermentation by roughly 10% and 7%, respectively. In this study, several varieties of corn stover lots were investigated to test the robustness of the deacetylation-pretreatment-saccharification-fermentation process.

Conclusions

Deacetylation shows significant improvement on glucose and xylose yields during pretreatment and enzymatic hydrolysis, but it also reduces hydrolyzate toxicity during fermentation, thereby improving ethanol yields and titer. The magnitude of effect is dependent on the selected corn stover variety, with several varieties achieving improvements of greater than 10% xylose yield in pretreatment, 20% glucose yield in low solids enzymatic hydrolysis and 7% overall ethanol yield.

【 授权许可】

   
2012 Chen et al; licensee BioMed Central Ltd.

【 图 表 】

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