Effect of structural changes of lignin during the autohydrolysis and organosolv pretreatment on Eucommia ulmoides Oliver for an effective enzymatic hydrolysis

Sulfur-free pulping of hot-water-extracted spruce sawdust

“…On the other hand, the lowest lignin content was determined from the black liquors, which were cooked from severely extracted wood (PHWE 2). As discussed above, enhanced delignification took place within a very narrow range of pre-treatment time, and significant decreases in lignin solubility and reactivity after harsh autohydrolysis conditions have been reported (Leschinsky et al 2008(Leschinsky et al , 2009Li, Gellerstedt 2008;Timilsena et al 2013;Zhu et al 2015). These observations were also in agreement with this study, as highly prolonged PHWE seemed to alter the structure of lignin in such a way that its dissolution was clearly hindered during the subsequent alkaline pulping.…”

“…Possible explanation could include, for example, various condensation reactions taking place during pretreatments, which rendered lignin structure insoluble and very resistant towards alkaline (but sulfur-free) cooking. This explanation was supported by previous studies (Leschinsky et al 2008;Li, Gellerstedt 2008;Timilsena et al 2013;Zhu et al 2015), in which a decreased delignification after harsh auto-hydrolysis conditions was observed. In these studies, it was also reported that the maximum extractability of lignin could be achieved within a very narrow range of reaction time, and a significant decrease in lignin solubility and reactivity was reported after harsh auto-hydrolysis conditions.…”

Lignocellulosic biomass to biofuels and biochemicals: A comprehensive review with a focus on ethanol organosolv pretreatment technology

“…The solvolytic cleavage of β‐O‐4 linkages under acidic conditions takes place by formation of w‐guaiacylacetone followed by formation of Hibbert's ketones (Figure a) or elimination of formaldehyde (Figure b; McDonough, ). M. Q. Zhu, Wen, Su, Wei, and Sun () studied the impact of acid‐catalyzed ethanol organosolv pretreatment on the nature of the isolated lignin. The content of β‐O‐4 linkage in milled wood lignin (MWL) of Eucommia ulmoides Oliver was 50.81/100 Ar, whereas no β‐O‐4 linkage remained in the ethanol organosolv lignin, indicating that ethanol organosolv delignification led to almost complete cleavage of this linkage under this condition.…”

Two‐step fractionation of Pinus radiata by autohydrolysis and organosolv delignification for enzymatic hydrolysis

“…The main product of the organosolv step is a pretreated solid rich in cellulose, which can be subjected to a step of enzymatic hydrolysis or simultaneous saccharification and fermentation (SSF) for glucose obtainment or bioethanol production, respectively . Furthermore, this delignification with an organic solvent allows the production of lignin with high purity and high chemical reactivity, which is considered as a valuable byproduct in the development of bio‐based materials and chemicals . For instance, organosolv wheat straw lignin has been applied as a substitute for phenol in a phenol–formaldehyde–resol resin .…”

“…For instance, organosolv wheat straw lignin has been applied as a substitute for phenol in a phenol–formaldehyde–resol resin . In addition, the incorporation of an AH step prior to organosolv involves the enhancement of delignification and improvement of enzymatic hydrolysis yield . Thus, the sequential pretreatment aims to maximize the utilization of isolated hemicelluloses and lignin but also improve the enzymatic hydrolysis of pretreated solid …”