Rapid mechanoenzymatic saccharification of lignocellulosic biomass without bulk water or chemical pre-treatment

Abstract

Lignocellulosic material is an abundant renewable resource with the potential to replace petroleum as a feedstock for the production of fuels and chemicals. The large scale deployment of biomass saccharification is, however, hampered by the necessity to use aggressive reagents and conditions, formation of side-products, and the difficulty to reach elevated monosaccharide concentrations in the crude product. Herein we report the high efficacy of Reactive Aging (or Raging, a technique where enzymatic reaction mixtures, without any bulk aqueous or organic solvent, are treated to multiple cycles of milling and aging) for gram-scale saccharification of raw lignocellulosic biomass samples from different agricultural sources (corn stover, wheat straw, and sugarcane bagasse). The solvent-free enzymatic conversion of lignocellulosic biomass was found to proceed in excellent yields (ca. 90%) at protein loadings as low as 2% w/w, without the need for any prior chemical pre-treatment or high temperatures, to produce highly concentrated (molar) monosaccharides. This crude product of mechanoenzymatic depolymerization is non-toxic to bacteria and can be used as a carbon source for bacterial growth.

Enzymatic depolymerization of highly crystalline polyethylene terephthalate enabled in moist-solid reaction mixtures

“…Using enzymes in moist-solid reaction mixtures rather than in traditional dilute solutions or slurries is an emergent strategy (36) that has proven beneficial for the breakdown of recalcitrant biopolymers such as cellulose (22,23), xylan (25), and chitin (26). Such reaction conditions provide a milieu that is closer to the natural setting of enzymes like HiC, which are secreted in the environment by microorganisms.…”

Clean Enzymatic depolymerization of highly crystalline polyethylene terephthalate in moist-solid reaction mixtures

“…Using enzymes in moist-solid reaction mixtures rather than in traditional dilute solutions is an emergent strategy(36) that has proven beneficial for the breakdown of recalcitrant biopolymers such as cellulose, (23,24) xylan, (25) and chitin (26). Such reaction conditions provide a milieu that is closer to the natural setting of enzymes like HiC, which are secreted in the environment by microorganisms.…”

“…Previous reports on the mechanoenzymatic breakdown of the biopolymers cellulose, (21,23,24) xylan (25), and chitin (26) demonstrated that enzyme kinetics under aging conditions are hyperbolic. These reactions can be accelerated by periodically repeating the milling process just before the yield reaches a plateau, in a process termed reactive aging (RAging).…”

Industrialization progress of lignocellulosic ethanol

“…While the pretreatment technology destroys the structure of lignocellulose and improves the enzymatic hydrolysis performance of raw materials, severe reaction conditions lead to a series of side reactions and produce a variety of complex compounds, mainly including furans, organic acids, and lignin derivatives [66][67][68][69]. All these substances have a complex shape and strongly inhibit the saccharification and fermentation processes, and these inhibitors must be removed, that is, the pretreated materials must be detoxified [46,62,70].…”