Bioethanol Production from Vineyard Waste by Autohydrolysis Pretreatment and Chlorite Delignification via Simultaneous Saccharification and Fermentation

In this paper, the production of a second-generation bioethanol from lignocellulosic vineyard cutting wastes was investigated in order to define the optimal operating conditions of the autohydrolysis pretreatment, chlorite delignification and simultaneous saccharification and fermentation (SSF). The autohydrolysis of vine-shoot wastes resulted in liquors containing mainly a mixture of monosaccharides, degradation products and spent solids (rich in cellulose and lignin), with potential utility in obtaining valuable chemicals and bioethanol. The autohydrolysis of the vine-shoot wastes was carried out at 165 and 180 °C for 10 min residence time, and the resulted solid and liquid phases composition were analysed. The resulted liquid fraction contained hemicellulosic sugars as a mixture of alpha (α) and beta (β) sugar anomers, and secondary by-products. The solid fraction was delignified using the sodium chlorite method for the separation of lignin and easier access of enzymes to the cellulosic sugars, and then, converted to ethanol by the SSF process. The maximum bioethanol production (6%) was obtained by autohydrolysis (165 °C), chlorite delignification and SSF process at 37 °C, 10% solid loading, 72 h. The principal component analysis was used to identify the main parameters that influence the chemical compositions of vine-shoot waste for different varieties.