A facile and fast method for quantitating lignin in lignocellulosic biomass using acidic lithium bromide trihydrate (ALBTH)

Abstract

A facile (one-step) and fast (30 min) method (ALBTH) was developed to quantitate lignin in lignocellulosic biomass; the method gave comparable results with the Klason method.

An uncondensed lignin depolymerized in the solid state and isolated from lignocellulosic biomass: a mechanistic study

“…Feedstocks (aspen, poplar, eucalyptus, Douglas fir, switchgrass, and corn stover) representing the three major biomass classes (hardwoods, softwoods, and grasses) were treated in the ALBTH system under mild reaction conditions (110°C, LiBr 60 wt% and 40 mM HCl) to investigate lignin depolymerization in the process of ALBTH treatment. By completely dissolving and hydrolyzing cellulose and hemicelluloses, the ALBTH treatment allowed quantitative isolation of lignin in the solid state from biomass, 28 as shown in Table S1. † The GPC-estimated molecular weights of the lignins are listed in Table 1 and compared with those of the corresponding isolated lignins, such as milled wood lignin (MWL) and cellulolytic enzyme lignin (CEL), estimated under similar chromatographic conditions.…”

“…26,27 The lignin fraction (ALBTH lignin) could be quantitatively obtained as the insoluble residue remaining after hydrolyzing the carbohydrates. 28 It was found to have a low molecular weight and was highly soluble in many common organic solvents, such as THF, acetone, acetic acid/water (95/5, v/v), dioxane/water (9 : 1, v/v), and DMSO (unpublished data). This feature distinguishes it from other isolated lignins such as Klason lignin and kraft lignin and indicates the uniqueness of lignin depolymerization in the ALBTH system.…”

Relationships between Cell Wall Digestibility and Lignin Content as Influenced by Lignin Type and Analysis Method

“…3a). Small amounts of acid-soluble lignin are reportedly lost during the KL procedure, especially from S-rich polymers (Musha and Goring, 1974;Li et al, 2016), and this in part could account for the differing slope coefficients observed among lignin types and the relatively low KL values for cell walls lignified with GS-and GSpCA-endwise polymers. Acid-soluble lignin is most often estimated by ultraviolet (UV) spectroscopy, but reliable quantitation is problematic because values are affected by UV absorbing degradation products derived from polysaccharides, and appropriate absorption coefficients for various types of lignin have not been clearly established (Sluiter et al, 2010).…”

“…3b), suggesting a common absorption coefficient can be implemented to analyze cell walls that are primarily lignified with these types of polymers. For similar reasons, care should also be taken when using other spectrophotometric methods (Suzuki et al, 2009;Li et al, 2016) that rely on generic absorption coefficients or standards for estimating lignin content. Overall, these observations suggest that caution should be exercised when interpreting ABSL estimates, particularly if plant materials contain low quantities of lignin or high proportions of bulk or atypical lignin polymers.…”

“…Overall, these observations suggest that caution should be exercised when interpreting ABSL estimates, particularly if plant materials contain low quantities of lignin or high proportions of bulk or atypical lignin polymers. For similar reasons, care should also be taken when using other spectrophotometric methods (Suzuki et al, 2009;Li et al, 2016) that rely on generic absorption coefficients or standards for estimating lignin content. As noted for the KL procedure, analysts should make use of thioacidolysis (Harman-Ware et al, 2016), gel-state 2D NMR (Kim and Ralph, 2010), or related analytical methods to detect shifts in lignin composition and structure that may affect ABSL estimates.…”