Evaluation of Agave Fiber Delignification by Means of Microscopy Techniques and Image Analysis

Abstract

Recently, the use of different types of natural fibers to produce paper and textiles from agave plants has been proposed. Agave atrovirens can be a good source of cellulose and lignin; nevertheless, the microstructural changes that happen during delignification have scarcely been studied. The aim of this work was to study the microstructural changes that occur during the delignification of agave fibers by means of microscopy techniques and image analysis. The fibers of A. atrovirens were obtained from leaves using convective drying, milling, and sieving. Fibers were processed using the Acetosolv pulping method at different concentrations of acetic acid; increasing acid concentration promoted higher levels of delignification, structural damage, and the breakdown of fiber clumps. Delignification followed by spectrometric analysis and microstructural studies were carried out by light, confocal laser scanning and scanning electron microscopy and showed that the delignification process follows three stages: initial, bulk, and residual. Microscopy techniques and image analysis were efficient tools for microstructural characterization during delignification of agave fibers, allowing quantitative evaluation of the process and the development of linear prediction models. The data obtained integrated numerical and microstructural information that could be valuable for the study of pulping of lignocellulosic materials.

Study of cellular architecture and micromechanical properties of cuajilote fruits (Parmentiera edulis D.C.) using different microscopy techniques

“…The lignin and photosynthetic pigments (chlorophylls) were monitored taking advantage of these compounds' autofluorescence. The excitation wavelengths used were 488 nm for lignin, and 405 nm for cellulose‐hemicellulose and chlorophylls (Hernández‐Hernández et al, 2014). In the case of raw fibers, staining was performed using a similar method with calcofluor for 5 min for cellulose‐hemicellulose, while for lignin, 0.01% safranin was used for 1 min and then washed with distilled water (Bond, Donaldson, Hill, & Hitchcock, 2008).…”

“…In the case of raw fibers, staining was performed using a similar method with calcofluor for 5 min for cellulose-hemicellulose, while for lignin, 0.01% safranin was used for 1 min and then washed with distilled water (Bond, Donaldson, Hill, & Hitchcock, 2008). The scanning mode was set to spectral planes, automatically generating the separation of the channels as reported by Hernández-Hernández et al (2014). The images were acquired by the ZEN software (Carl Zeiss, Germany), in 8 bits, RGB color and stored in TIFF format at 1024 × 1,024 pixels.…”

“…Thus, it is necessary to carry out studies related to these issues, starting with the physicochemical characterization at different maturity stages which will provide valuable information on the plant's potential as a source of lignocellulosic materials (Sanjay et al, 2018). Moreover, microscopy techniques in combination with image analysis, microindentation and X‐ray diffraction (XRD) will yield important information about cellular structure, distribution and relative abundance of the biopolymers into plant materials and the crystalline arrangement of their structural components, as well as new data on the fibers' hardness and stiffness (Hernández‐Hernández et al, 2014; Marin‐Bustamante et al, 2018; Wu et al, 2010).…”

Spectroscopic and Microscopic Study of Peroxyformic Pulping of Agave Waste

“…Image analysis provides useful numerical information for evaluation of the delignification process. Thus, in order to evaluate quantitatively the images obtained by CLSM, the methodology reported by Hernández-Hernández et al (2014) was used. According with this report, gray level (GL) values of images can be used as a measure of the intensity of fluorescence images and consequently with the relative content of lignin or cellulose on the fiber surface.…”

“…The changes to lignin and cellulose in the fibers during the peroxyformic treatment were monitored by CLSM using a similar procedure as that reported previously (Hernández-Hernández et al, 2014). Pulp samples from selected experimental design experiments were observed directly on a glass slide in a CLSM (LSM 710, Carl Zeiss, Germany).…”