Supramolecular Deconstruction of Bamboo Holocellulose via Hydrothermal Treatment for Highly Efficient Enzymatic Conversion at Low Enzyme Dosage

Abstract

Hydrothermal pretreatment (HTP) has long been considered as an efficient and green treatment process on lignocellulosic biomass for bioconversion. However, the variations of cellulose supramolecular structures during HTP as well as their effects on subsequent enzymatic conversion are less understood. In this work, bamboo holocellulose with well-connected cellulose and hemicelluloses polysaccharides were hydrothermally treated under various temperatures. Chemical, morphological, and crystal structural determinations were performed systematically by a series of advanced characterizations. Xylan was degraded to xylooligosaccharides in the hydrolyzates accompanied by the reduced degree of polymerization for cellulose. Cellulose crystallites were found to swell anisotropically, despite the limited decrystallization by HTP. Hydrogen bond linkages between cellulose molecular chains were weakened due to above chemical and crystal variations, which therefore swelled, loosened, and separated the condensed cellulose microfibrils. Samples after HTP present notably increased surface area, favoring the adsorption and subsequent hydrolysis by cellulase enzymes. A satisfying enzymatic conversion yield (>85%) at rather low cellulase enzyme dosage (10 FPU/g glucan) was obtained, which would indicate new understandings on the green and efficient bioconversion process on lignocellulosic biomass.

The Chemical Characterisation of the Maritime Pine Bark Cultivated in Northern Portugal

“…This parameter is based on distinguishing between a crystalline phase and an amorphous phase of the material. The XRD diffraction patterns of holocellulose and cellulose shown in Figure 4 exhibit three distinct diffraction peaks near the 2θ angles of 16 • , 22 • , and 34 • , revealing that the crystalline structure of the samples was cellulose, as described in previous literature [83]. However, α-cellulose exhibits a broader 2θ peak ranging from 15.0 • to 25.0 • ; these variations may be possibly due to the highly amorphous nature of the synthesised cellulose [73].…”

“…In this process, the fundamental parameter approach was applied for phase quantification. The crystallinity index (CrI) was determined by calculating the intensities in the crystalline and amorphous regions following Equation (1) [83], representing the intensities in the crystalline and amorphous regions at peak located at approximately 2θ = 21.54-22.368 • and 12.512-16.731 • , respectively:…”

Efficacy and Functional Mechanisms of a Two-Stage Pretreatment Approach Based on Alkali and Ionic Liquid for Bioconversion of Waste Medium-Density Fiberboard

“…The NaOH and AAI pretreatments lead to the formation of a porous and rough surface on MDF (red circle in the picture), suggesting that the pretreatment disrupts the cellulose-hemicellulose-lignin matrix and removes some external fibers. This alteration enhances the enzymes' accessibility to cellulose, thereby increasing the sugar yield from enzymatic hydrolysis [42,43]. In contrast, Figure 6b shows that MDF surfaces treated solely with NaOH exhibit partial deformation and structural disintegration, potentially showing lignin hydrolysis, which serves as the structural backbone for microfibril integrity.…”

A study revealing mechanisms behind the stone cell of Yali pear degradation by mixed‐culture fermentation of lactic acid bacteria and yeast

“…Cellulose is an unbranched chain of polymer of glucose monomers linked by β‐1,4 glycosidic bonds. Hydrogen bonds can be formed within and between cellulose molecules, and the existence of these structures hinders the degradation of cellulose (Wang, Wang, et al, 2022). Therefore, breaking inter‐ and intramolecular chemical bonds and reducing the crystallinity of cellulose are key to its degradation.…”