Enhancing Lignocellulosic Biomass Hydrolysis by Hydrothermal Pretreatment, Extraction of Surface Lignin, Wet Milling and Production of Cellulolytic Enzymes

Abstract

Acetone and ethanol extraction of lignin deposits from the surface of hydrothermally (liquid hot water) pretreated beech wood biomass alleviates the lignin inhibitory effects during enzymatic hydrolysis of cellulose to glucose and boosts the enzymatic digestibility to high values (≈70 %). Characterization of the extracted lignins (FTIR, pyrolysis/GC–MS, differential thermogravimetry, gel permeation chromatography) indicated high purity, low molecular weight, and features that suggest that it consists mainly of fragments of the native wood lignin partially depolymerized and recondensed on the biomass surface during the hydrothermal pretreatment. The pyrolysis products of the extracted surface lignins suggest their high potential as a feedstock for the production of high added value phenolic compounds. When the enzymatic hydrolysis of the pretreated and extracted biomass solids was assisted by mild wet milling, near complete cellulose digestibility (≥95 %) could be achieved. In the context of the biorefinery and whole‐biomass valorization concept, it was also shown that the hydrothermally (hemicellulose‐deficient) pretreated and delignified biomass solids could be also successfully used for the production of crude cellulase from Trichoderma reesei cultures, providing a simple and low‐cost method for the complementary production of cellulases by utilizing fractions of the integrated hydrolysis process.

Interaction of enzymes with lignocellulosic materials: causes, mechanism and influencing factors

“…The enzymatic cellulose degradation is hindered during prolonged reaction on biomass surfaces due to the inaccessibility of enzymes to the cellulose caused by the slow and regular accumulation of lignin (Djajadi et al 2018). The lignin-rich components of biomass adsorbs enzymes more than non-lignin components, this type of adsorption is non-productive because it ceases the hydrolysis of feedstock (Nitsos et al 2019;Yang et al 2019). Adsorption onto lignin is non-productive, and hence disadvantageous for process economics.…”

Potassium permanganate assisted organosolv pretreatment enhances enzymatic hydrolysis of corn stover

“…Scans are selected from scattering angle (2θ) =5°-60° with a scan rate of 4°/min at 40 kV voltage and 40 mA current by a generator. Crystallinity index is calculated by Formula (3) (Nitsos et al, 2019):…”

Lignocellulosic Waste Pretreatment Solely via Biocatalysis as a Partial Simultaneous Lignino-Holocellulolysis Process

“…Pretreating lignocellulosic waste is a mandatory phase to accomplish hydrolysis of biorefinery feedstock aimed at producing value-added products, i.e., fermentable sugar (highest release of reducing sugars, i.e., up to 10.70 ± 0.14 g/Kg biomass of glucose and 12.41 ± 0.34 g/Kg biomass of xylose from lignocellulose waste [41]), in biorefinery processes [48]. Pretreatment facilitates ligninolysis and consequently, uncovering holocelluloses for the subsequent successful hydrolysis of the lignocellulosic waste with negligible energy intake, to accomplish the outmost fermentable sugar extraction [49,50]. Numerous techniques, such as hot water, dilute sulphuric etc., have been utilized to eliminate the recalcitrant lignin in lignocellulosic waste focusing on the feedstock being beneficiated to mitigate environmental pollution.…”