Valorization of Side-Streams from a SSF Biorefinery Plant: Wheat Straw Lignin Purification Study

Abstract

The lignocellulosic materials produced after each step of a biorefinery plant using simultaneous saccharification and fermentation (SSF) technology on wheat straw (Triticum spp.) for bioethanol production were characterized by spectroscopic and chromatographic techniques in order to investigate the macromolecular interactions between the lignin and polysaccharides. In order to valorize the lignin cakes, a purification step was set up and the extraction conditions (acid pretreatment, temperature, time, and NaOH concentration) were optimized by a chemiometric approach in terms of yield and purity. Residual carbohydrate impurities, free and/or chemically bonded to lignin (lignin carbohydrates complexes), were individuate as the most critical factor for a satisfactory lignin extraction. Finally, the lignin samples collected according to the optimized extraction conditions were chemically characterized and low molecular weight, high phenols concentration, and low carboxylic acids content were recognized as interesting features for industrial applications.

Protic Ionic Liquids for Lignin Extraction—A Lignin Characterization Study

“…The MW and dispersity of any biopolymer (like lignin) are important properties that have been shown to affect the performance and consequent application of lignin in the development of high value bioproducts [ 38 , 42 ]. Therefore, the ability to control or tailor these properties is of high importance to end users of lignin for various applications [ 38 , 40 , 41 ]. Analyses of the average MW of lignin can also provide insight into the fragmentation pattern of lignin during PIL dissolution/extraction, which can be used to develop further understanding of the mechanisms that promote lignin dissolution in PILs.…”

“…Analyses of the average MW of lignin can also provide insight into the fragmentation pattern of lignin during PIL dissolution/extraction, which can be used to develop further understanding of the mechanisms that promote lignin dissolution in PILs. For this study, all lignin samples were acetylated, dissolved in THF, and subsequently, analyzed using a GPC for their MWD [ 30 , 38 , 39 , 40 , 41 ]. Investigations were performed on the kraft lignin samples recovered after PIL dissolution (PIL-K. lignin), as well as the lignin samples that were recovered after extraction from corn stover (PIL-CS lignin).…”

“…The MWs and dispersity of the lignin recovered directly from corn stover ([Pyrr][Ac]-CS lignin) are lower than for any of the kraft lignin samples. This indicates that the regenerated lignin had a more homogenous distribution ( Table 1 ), which could be a property of high interest for applications were purity, uniformity and quality control is of significance [ 38 , 40 , 41 ].…”

“…(FTIR) is a simple non-destructive technique, which can be utilized to obtain quick and accurate information about the structure of lignin [ 37 ]. The molecular weight (MW) of lignin is a fundamental property that influences the valorization of lignin, and can be readily measured using gel permeation chromatography (GPC) [ 38 , 39 , 40 , 41 ]. The effect of the solvent used to regenerate the lignin was also considered.…”

Alternatives for Chemical and Biochemical Lignin Valorization: Hot Topics from a Bibliometric Analysis of the Research Published During the 2000–2016 Period

“…The potential of Kraft and soda lignins as feedstock for value added products has been investigated to identify the most adequate pulping conditions [88][89][90]. Moreover, alkaline delignification processes inspired by traditional pulping have been proposed for integral lignocellulosic biomass valorization [91][92][93][94][95]. Table 6.…”