Dilute Acid Hydrolysis of Wheat Straw Oligosaccharides
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The dilute acid posthydrolysis of wheat straw hemicellulosic oligosaccharides obtained by autohydrolysis was evaluated. An empirical model was used to describe the effect of catalyst concentration (sulfuric acid, 0.1–4% w/w) and reaction time (0–60 min) based on data from a Doehlert experimental design. Catalyst concentration is the main variable influencing posthydrolysis performance, as both its linear and quadratic coefficients are statistically significant for the majority of the studied variables, namely, the ones related to sugar and byproducts production. Reaction time influences xylose and furan derivatives concentrations but not phenolics or acetic acid content. Catalyst concentration and reaction time interact synergistically, minimizing sugar recovery and promoting furan derivatives production. Based on the proposed models, it was possible to delimit an operational range that enables to obtain high monosaccharides recovery together with a slight decrease in inhibitors content as compared to the standard acid hydrolysis treatment. Furthermore, this is achieved with up to 70% less acid spending or considerable savings on reaction time.
KeywordsAutohydrolysis Dilute acid posthydrolysis Experimental design Hemicellulosic hydrolyzate Wheat straw Xylooligosaccharides
Authors are grateful to Fundação para a Ciência e a Tecnologia (FCT) for the financial support of this work (project BIOREFINO PTDC/AGR-AAM/71533/2006). Talita Silva-Fernandes gratefully acknowledges the grant funded by CEBio (Prime-IDEIA-AdI Projecto no. 70/00326). The authors thank J. C. Roseiro for the helpful discussions and Amélia Marques, Carlos Barata, and Céu Penedo for their technical support.
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