Abstract
BackgroundComplexity and high cost are the main limitations for high-throughput screening methods for the estimation of the sugar release from plant materials during bioethanol production. In addition, it is important that we improve our understanding of the mechanisms by which different chemical components are affecting the degradability of plant material. In this study, Fourier transform infrared photoacoustic spectroscopy (FTIR-PAS) was combined with advanced chemometrics to develop calibration models predicting the amount of sugars released after pretreatment and enzymatic hydrolysis of wheat straw during bioethanol production, and the spectra were analysed to identify components associated with recalcitrance.ResultsA total of 1122 wheat straw samples from nine different locations in Denmark and one location in the United Kingdom, spanning a large variation in genetic material and environmental conditions during growth, were analysed. The FTIR-PAS spectra of non-pretreated wheat straw were correlated with the measured sugar release, determined by a high-throughput pretreatment and enzymatic hydrolysis (HTPH) assay. A partial least square regression (PLSR) calibration model predicting the glucose and xylose release was developed. The interpretation of the regression coefficients revealed a positive correlation between the released glucose and xylose with easily hydrolysable compounds, such as amorphous cellulose and hemicellulose. Additionally, a negative correlation with crystalline cellulose and lignin, which inhibits cellulose and hemicellulose hydrolysis, was observed.ConclusionsFTIR-PAS was used as a reliable method for the rapid estimation of sugar release during bioethanol production. The spectra revealed that lignin inhibited the hydrolysis of polysaccharides into monomers, while the crystallinity of cellulose retarded its hydrolysis into glucose. Amorphous cellulose and xylans were found to contribute significantly to the released amounts of glucose and xylose, respectively.Electronic supplementary materialThe online version of this article (doi:10.1186/s13068-015-0267-2) contains supplementary material, which is available to authorized users.
Highlights
Complexity and high cost are the main limitations for high-throughput screening methods for the estimation of the sugar release from plant materials during bioethanol production
In addition to the low root-mean-square error (RMSE), the differences between cross-validation and the external validation results were quite small, which indicated that the calibrations were robust. These results proved the potential use of calibrations based on Fourier transform infrared (FTIR)-PAS for the prediction of sugar release from wheat straw
This study established that FTIR-PAS can be used to predict the bioethanol potential from wheat straw and in addition provide structural information on the chemical compounds involved in saccharification
Summary
Complexity and high cost are the main limitations for high-throughput screening methods for the estimation of the sugar release from plant materials during bioethanol production. To select the best cultivars, it is desirable to assess the potential for sugar release after pretreatment and hydrolysis of a large number of cultivars For this purpose, high-throughput screening methods have been developed [7,8,9]. Good prediction accuracy can be achieved using this technique, but it provides limited information about the chemical components that are associated with the propensity to release sugars. The reason for this is that the near infrared (NIR) spectra mostly reflect overtones and the combination bands of the chemical bonds, which are highly overlapping [14]
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