title: Facile isothermal solid acid catalyzed ionic liquid pretreatments to enhance the combined sugars production from Arundo donax Linn.
abstract: BACKGROUND
  Solid 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.
  
  
  RESULTS
  The 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.
  
  
  CONCLUSIONS
  Isothermal [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.
authors: Beijing Key Laboratory of Lignocellulosic Chemistry, Beijing Forestry University, Beijing, 100083 China.
authors: Tingting
authors: T
authors: You
authors: Beijing Key Laboratory of Lignocellulosic Chemistry, Beijing Forestry University, Beijing, 100083 China.
authors: Lupeng
authors: L
authors: Shao
authors: Beijing Key Laboratory of Lignocellulosic Chemistry, Beijing Forestry University, Beijing, 100083 China.
authors: Ruizhen
authors: R
authors: Wang
authors: Beijing Key Laboratory of Lignocellulosic Chemistry, Beijing Forestry University, Beijing, 100083 China.
authors: Liming
authors: L
authors: Zhang
authors: Beijing Key Laboratory of Lignocellulosic Chemistry, Beijing Forestry University, Beijing, 100083 China.
authors: Feng
authors: F
authors: Xu
keywords: Acid enhanced ionic liquid pretreatment; Arundo donax Linn.; Enzymatic hydrolysis; Total reducing sugars