Investigation of the Effects of Ionic Liquid 1-Butyl-3-methylimidazolium Acetate Pretreatment and Enzymatic Hydrolysis of Typha capensis

摘要

Pretreatment of Typha capensis (TC) with ionic liquid (EL) 1-butyl-3-methylimidazolium acetate [BMIM(OAc)] shows that the structural integrity-like degree of polymerization, polydispersity index, and lignin were altered, providing easy access to enzymes, and improved its digestibility to fermentable sugars. Hydrolysis of pretreated samples by a pre-optimized mixture of cellulose enzymes achieved an optimal reducing sugar yield (RSY) of 82.4 g/100 g after 6 h of pretreatment incubation. Because the costs of ILs are high, pre-hydrorysis and recycling are used to improve the economics. Pre-hydrolysis steps using sodium hydroxide followed by IL treatment were found to be better than sulfuric acid pre-hydrolysis followed by EL. Pre-hydrorysis treatment with alkali reduced pretreatment time from 6 h to 15 min, and total solid (TS) was increased from 5 to 10% without significant reduction in the glucose and RSYs. During solvent recycling, about 10% of initial lignin at each cycle was being accumulated into the liquid stream containing the IL, with minimal traces of carbohydrates. Treatment of the recycled IL at 10th and 15th cycles enabled recovery of about 93% of the IL-soluble lignin released into the liquid stream and improved the effectiveness of pretreatment The investigation reveals the possibility of improving EL pretreatment outcome by increasing the TS through NaOH pre-hydrolysis. With the possible recycling of the IL up to 15 cycles, the overall costs of using this procedure are considerably reduced.