Multiproduct biorefinery from vine shoots: Bio-ethanol and lignin production

Vine shoots were hydrothermally processed and the effect of the different assayed severities on the subsequent enzymatic saccharification of the remaining solids was evaluated. The solid obtained at a severity of 4.47 showed the highest yield on glucose (74.01%) and therefore, it was used as the substrate for the obtaining of bio-ethanol through a SSF process. Under the evaluated conditions (LSR 10 g/g, 20 FPU/g and 10 IU/FPU) 13.3 g/L of bio-ethanol were produced (corresponding to 67.4% of ethanol conversion). Moreover, lignin has been extracted by an alkali delignification treatment from the vine shoots unprocessing and from the solids resulting from the stages of the proposed biorefinery scheme, which were the autohydrolysed vine shoots and the bio-ethanol residue. The isolated lignins were characterized by HPLC, total phenolic content, FTIR, HPSEC, Py-GC/MS and TGA and it was observed that the successive stages of processing to which the vine shoots were submitted provoked chemical and structural changes in the extracted lignins. The knowledge of the structural modifications that the lignin present in the vine shoots during the autohydrolysis and the SSF process could help determining at which stage of the bio-ethanol production would be suitable to recover the lignin for value-added applications. (C) 2019 Elsevier Ltd. All rights reserved.