Facile isothermal solid acid catalyzed ionic liquid pretreatments to enhance the combined sugars production from Arundo donax Linn.

Abstract

BackgroundSolid acid catalyzed inexpensive ionic liquid (IL) pretreatment is promising because of its effectiveness at decreasing biomass recalcitrance to subsequent enzymatic hydrolysis or in situ hydrolysis of carbohydrate oligomers. However, the conventional strategy was limited by the complex non-isothermal process and considering only one aspect of sugar recovery. In this study, facile isothermal pretreatments using Amberlyst 35DRY catalyzed 1-n-butyl-3-methylimidazolium chloride ([C4mim]Cl) at mild conditions were developed on bioenergy crop Arundo donax Linn. to enhance the combined sugars released. The physicochemical differences, enzymatic digestibility, and sugars released in situ were evaluated and compared to define the best set of conditions.ResultsThe optimized isothermal pretreatment (110 °C, IL for 3 h, Amberlyst for 1 h) resulted in significant enhancement in combined sugars released (58.4 g/100 g raw materials), recovering 85.0 % of the total reducing glycan in the raw biomass. This remarkable improvement could be correlated to cellulose crystallinity reduction, crystalline conversion, and partial removal of the main chemical components caused by the pretreatment. Particularly, solubilization of hemicelluloses and partial depolymerization of cellulose contributed to the synergetic improvement of sugars production in enzymatic hydrolysis and in situ. Irrespective of the generous differences in mass recovery, the highest cellulose digestibility of 90.2 % and sugar released of 43.0 % (based on initial materials) in the pretreatment liquor were obtained. Interestingly, lignin (0.8–6.1 %) and sugars derived lactic acid (4.70–5.94 %) were produced without any notable deleterious effects.ConclusionsIsothermal [C4mim]Cl-Amberlyst pretreatment was a highly effective, simple, and convenient process that produced high yields of fermentable sugars from recalcitrant biomass by in situ hydrolysis of soluble biomass and enhancement of cellulose digestibility of the regenerated biomass. Relatively high amount of new revenues beyond sugars of this pretreatment could promote the commercial viability.Electronic supplementary materialThe online version of this article (doi:10.1186/s13068-016-0589-8) contains supplementary material, which is available to authorized users.

High Purity and Low Molecular Weight Lignin Nano-Particles Extracted from Acid-Assisted MIBK Pretreatment

“…After the pretreatment, however, the MIBK-lignin was decreased to 767 and 1227 in M n and M w, respectively, indicating the linkages between lignin units, generally, the aryl ether linkages were broken. According to the previous results [21,[26][27][28] showed in Table 2, the molecular weights of the extracted lignin from other systems and deep eutectic solvents (DESs), etc., still remained in several thousand grams per mole, which may ascribe to the condensation of the small lignin fractions by forming excess carbon-carbon bonds. This indicated, in some way, that less condensation occurred during the pretreatment of MIBK-lignin, which is considered as the result of the weak acidic conditions and the protection of the MIBK phase.…”

“…However, it is still unsatisfactory in the recovery of the hemicellulose and lignin. Although current studies on pretreatment systems for removing lignin or breaking the biomass recalcitrance has focused on the ionic liquids (ILs) [23][24][25][26][27] and deep eutectic solvents (DESs) pretreatments [28][29][30][31][32], the challenge of the cellulose valorization without compromises of lignin and hemicellulose fractions is still unresolved.…”

Reconstruction of lignin and hemicelluloses by aqueous ethanol anti‐solvents to improve the ionic liquid‐acid pretreatment performance of Arundo donax Linn

“…The pretreatment was conducted in a three‐neck flask (total volume of 100 ml). 1.5 g of raw A. donax was pretreated with 28.5g of IL at 120°C with mechanical stirring at 175 rpm for 3 hr, and then 0.3 g of Amberlyst 35DRY was added and kept at temperature for 1 hr (You, Shao, Wang, Zhang, & Xu, ). After the reaction, different anti‐solvents were applied for cellulose regeneration to obtain pretreated samples with different structure.…”

“…Recently, ionic liquid (IL) based pretreatment that involved acid in less expensive IL 1‐n‐butyl‐3‐methylimidazolium chloride ([C 4 mim]Cl) was developed to boost the yield of sugars from lignocellulose (Groff et al, ; You, Shao, Wang, Zhang, & Xu, ). In a typical IL‐acid pretreatment process, the lignocellulose is partially dissolved in IL, following by acid catalysis to form a biomass slurry.…”

“…Typically, water is the most widely used anti‐solvent for cellulose regeneration due to its low cost. However, the coalesced polymers such as lignin and pseudo lignin droplets were apt to deposit on the surface of cellulose during an acidic pretreatment when using water as the precipitation or reaction media (Sannigrahi, Kim, Jung, & Ragauskas, ; You et al, ). It has been demonstrated that high surface coverage by lignin can act as physical barriers to block enzyme accessibility to the substrate for sugar production (Kumagai, Lee, & Endo, ; Kumar et al, ).…”