Fractionation of Cynara cardunculus L. by Acidified Organosolv Treatment for the Extraction of Highly Digestible Cellulose and Technical Lignin

Abstract

One of the primary targets for the new lignocellulosic feedstock-based biorefinery is the simultaneous valorization of holocellulose and lignin. Acidified organosolv treatment is among the most promising strategy for recovering technical lignin, water-soluble hemicellulose, and cellulose pulp with increased accessibility to hydrolytic enzymes. In this work, a design-of-experiment (DoE) approach was used to increase the cellulose recovery, digestibility, and the delignification of Cynara cardunculus L. feedstock. In the first treatment, the milled biomass was subjected to microwave-assisted extraction using an acidified GVL/water mixture to separate lignin and hemicellulose from cellulose. In the second treatment, the cellulose pulp was hydrolyzed by cellulolytic enzymes to demonstrate the enhanced digestibility. At the optimal condition (154 °C, 2.24% H2SO4, and 0.62 GVL/water ratio), the cellulose pulp showed a cellulose content of 87.59%, while the lignin content was lower than 8%. The cellulose recovery and digestibility were equal to 79.46% and 86.94%, respectively. About 40% of the initial hemicellulose was recovered as monosaccharides. This study demonstrated the effectiveness of the two-step organosolv treatment for biomass fractionation; however, as suggested by DoE analysis, a confirmative study at a low temperature (<154 °C) should be performed to further increase the cellulose recovery.

Bioactive Compounds from Cardoon as Health Promoters in Metabolic Disorders

“…Lignocellulosic biomass (cellulose, hemicellulose, and lignin) is the most abundant renewable resource on earth. This biomass is resistant to enzymatic and chemical degradation and possesses a protective function against natural agents and microbial attacks [59,60]. Cardoon is a lignocellulosic plant, in which lignocellulosic residues represent around 70-80% of the cardoon plant [61].…”

“…The contents of their vegetal parts range from 4.6 to 55.2 g/100 g d.w. Stems were revealed to have higher amounts (Table 3) [10,35,45,58,60,62,63].…”

“…Lignocellulose is naturally recalcitrant, whereby enzymatic hydrolysis of cellulose is extremely difficult compared to the breakdown of other renewable vegetal materials, such as starch [58,60]. Developing methods for primary fractionation depends on their economic assessment and environmental impact [58,59].…”

“…Cellulose is probably the most abundant and valuable component of lignocellulosic biomass; it is a long-chain polymer, described as the most structural component in plant cells and tissues [64,65]. Its content in cardoon vegetal parts varies between 10.33% and 51.7%, with its greatest content being found in the stems [10,35,45,58,60,62,63]. Cellulose is a versatile polymer, being utilized by several sectors, such as veterinary foods, wood and paper, fiber and clothes, and cosmetics and pharmaceuticals as an excipient [65].…”

“…Moreover, the residual cellulose is a great source of cellulosic fibers, which can be submitted to a saccharification process to obtain a valuable source of fermentable sugars, such as glucose, used for bioethanol production and other industrial applications [59]. The content of hemicellulose in cardoon materials varies between 4.6% and 55.2% (Table 3), with the stalks having the greatest content [10,35,45,58,60,62,63].…”