Prediction of Lignin Contents from Infrared Spectroscopy: Chemical Digestion and Lignin/Biomass Ratios of Cryptomeria japonica.

A method for the high-throughput analysis of the relative lignin contents of Cryptomeria japonica samples over a wide concentration range (3-73%), independent of the type of chemical pretreatment, was developed by using Fourier transform infrared spectroscopy. First, the assignments of the infrared absorbance related to lignin were reviewed. Then, various chemical treatments, including alkaline, acid, and hydrothermal processes, and a sodium chlorite oxidation treatment, were performed to prepare samples containing a wide range of different lignin contents. Principal component analysis indicated high variability among the chemical treatments in terms of the corresponding lignin contents as well as the resulting changes in the chemical structure of hemicellulose; this conclusion was supported by the loading vectors. The intensity of the key band of lignin at 1508 cm-1 was calculated using the absorbance at 2900 cm-1 as a reference; a reliable calibration curve with an R2 of 0.968 was obtained independent of the chemical treatment performed. This simple and rapid method for determining the lignin content is expected to be widely applicable for optimizing bioethanol production, as well as monitoring biomass degradation processes.

A comparative study of the biomass properties of Erianthus and sugarcane: lignocellulose structure, alkaline delignification rate, and enzymatic saccharification efficiency.

A comprehensive understanding of the structure and properties of gramineous lignocelluloses is needed to facilitate their uses in biorefinery. In this study, lignocelluloses from fractionated internode tissues of two taxonomically close species, Erianthus arundinaceus and sugarcane (Saccharum spp.), were characterized. Our analyses determined that syringyl (S) lignins were predominant over guaiacyl (G) or p-hydroxyphenyl (H) lignins in sugarcane tissues; on the other hand, S lignin levels were similar to those of G lignin in Erianthus tissues. In addition, tricin units were detected in sugarcane tissues, but not in Erianthus tissues. Distributions of lignin inter-monomeric linkage types were also different in Erianthus and sugarcane tissues. Alkaline treatment removed lignins from sugarcane tissues more efficiently than Erianthus tissues, resulting in a higher enzymatic digestibility of sugarcane tissues compared with Erianthus tissues. Our data indicate that Erianthus biomass displayed resistance to alkaline delignification and enzymatic digestion.