Unconventional Pretreatment of Lignocellulose with Low‐Temperature Plasma

Abstract

Lignocellulose represents a potential supply of sustainable feedstock for the production of biofuels and chemicals. There is, however, an important cost and efficiency challenge associated with the conversion of such lignocellulosics. Because its structure is complex and not prone to undergo chemical reactions very easily, chemical and mechanical pretreatments are usually necessary to be able to refine them into the compositional building blocks (carbohydrates and lignin) from which value-added platform molecules, such as glucose, ethylene glycol, 5-hydroxymethylfurfural, and levulinic acid, and biofuels, such as bioderived naphtha, kerosene, and diesel fractions, will be produced. Conventional (wet) methods are usually polluting, aggressive, and highly energy consuming, so any alternative activation procedure of the lignocellulose is highly recommended and anticipated in recent and future biomass research. Lignocellulosic plasma activation has emerged as an interesting (dry) treatment technique. In the long run, in particular, in times of fairly accessible renewable electricity, plasma may be considered as an alternative to conventional pretreatment methods, but current knowledge is too little and examples too few to guarantee that statement. This review therefore highlights recent knowledge, advancements, and shortcomings in the field of plasma treatment of cellulose and lignocellulose with regard to the (structural and chemical) effects and impact on the future of pretreatment methods.

Microbial Lipid Production from Corn Stover by the Oleaginous Yeast Rhodosporidium toruloides Using the PreSSLP Process

“…Cellulose is composed of glucose unit and hemicellulose is composed of pentoses and hexoses such as xylose, arabinose and galactose units. However, cellulose, hemicellulose and lignin form very complex and recalcitrant structures that present a major challenge for fractionation and utilization [6]. A pretreatment step is usually required to breakdown interactions among cellulose, hemicellulose and lignin to increase the enzymatic digestibility [7,8].…”

Nitrogen plasma surface treatment for improving polar ink adhesion on micro/nanofibrillated cellulose films

“…The increased contribution of the polar component in the FSE donated by the cationic N adsorption under plasma exposure is, therefore, expected to enhance the compatibility with the application of highly polar inks, especially if their components are anionic (Vanneste et al 2017;Ma et al 2010;Hoth et al 2008). The images in Fig.…”

“…We also identify a correlation between the observed change in free surface energy of the MNFC film, arising from the plasma treatment, with the effect of the enzymatic pretreatment. This is related to the level of residual crystallinity increasing as a function of progressive enzymatic pretreatment (Galagan et al 2011;Cernakova et al 2006;Pertile et al 2010;Vanneste et al 2017).…”

Oxygen-radical pretreatment promotes cellulose degradation by cellulolytic enzymes

“…Similar results were also observed using other grades of cellulose (α-cellulose, bacterial cellulose, and cotton). Although the exact mechanism of cellulose depolymerization by plasma treatment is not yet fully elucidated, plasma treatment would likely generate radicals in the gas phase, which react with glucosyl units on the surface of cellulose to form radicals that lead to bond cleavage [ 2 ]. The most favorable cleavage occurs at the β-1,4-glycoside linkage, as suggested by electron spin resonance spectroscopy analysis [ 44 , 45 ].…”

“…Cellulose is the most abundant polysaccharide found in nature, consists of a β-1,4-linked linear chain of glucose units, and is used in the biofuel, oil, food, textile, and pulp industries [ 1 , 2 ]. Cellulolytic enzymes are important reagents in industrial biorefinery processes, such as the production of biofuels from plant biomass [ 3 ].…”