Reducing Cellulose Crystallinity with a Noncellulose-Dissolving Solid Zwitterion and Its Application for Biomass Pretreatment

Abstract

One-pot ethanol production from plant biomass (successive biomass pretreatment, enzymatic hydrolysis, and fermentation in a single vessel) is necessary for the practical production of second-generation bioethanol because multipot procedures require large energy inputs. One-pot ethanol production requires low-toxicity cellulose solvents, and liquid zwitterions are the most promising candidates. However, liquid zwitterions have complex synthetic procedures, which significantly increases the energy cost. Here, the applicability of low-toxic simple zwitterions was investigated from the viewpoint of pretreatment ability for one-pot ethanol production. In this study, a simple solid noncellulose dissolving zwitterion was able to reduce the crystallinity of microcrystalline cellulose. The pretreatment of cellulose was performed in a zwitterion/water mixture at 100 °C while removing water. The imidazolium cation and carboxylate anion are key structures for an efficient pretreatment. Cellulose pretreated with the solid zwitterion was susceptible to hydrolysis, and the hydrolysis efficiency was comparable to that of the liquid zwitterion, which dissolves cellulose. The simple solid zwitterion was also effective for biomass pretreatment. The zwitterion delignified as well as reduced crystallinity, resulting in the pretreatment of bagasse. The pretreatment ability for bagasse was comparable to that of liquid zwitterions.

A simple overview of toxicity of ionic liquids and designs of biocompatible ionic liquids

“…4) are also promising candidates for efficient bioethanol production. [80][81][82]91,92 Their low toxicity is remarkable, and fermentation can occur in an aqueous solution containing more than 50 wt% of the zwitterion. 80 The zwitterions can dissolve cellulose like [C 2 mim]OAc, which is another advantage in biomass pretreatment.…”

Bioethanol fermentation in the presence of ionic liquids: mini review

“…OE 2 imC 3 C, which combines an imidazolium cation with a carboxylic acid anion, can not only perform delignification and reduce cellulose crystallinity, but also dissolution of cellulose. 45,48,[68][69][70] In addition, microbial fermentation is possible even in OE 2 imC 3 C solutions of more than 50 wt%, showing its extremely low toxicity. 48…”

Bonding Wood via Cellulose Aqueous Solution as Cell Wall Adhesive

“…However, cellulose microfibers have a highly aggregate structure, which is composed of cellulose molecular chains arranged in an orderly manner through mutual hydrogen bonding. [22] The use of green and inexpensive cellulose aqueous solvents is an effective to dissolve cellulose microfibrils and to directly obtain aqueous solutions containing highly defibrillated cellulose. [23,24] As far as we know, cellulose aqueous solution (contains dissolved cellulose) as an environmentally friendly bio-based wood adhesive has yet never been systematically studied.…”