title: Multilevel composition fractionation process for high-value utilization of wheat straw cellulose.
abstract: BACKGROUND
  Biomass refining into multiple products has gained considerable momentum due to its potential benefits for economic and environmental sustainability. However, the recalcitrance of biomass is a major challenge in bio-based product production. Multilevel composition fractionation processes should be beneficial in overcoming biomass recalcitrance and achieving effective conversion of multiple compositions of biomass. The present study concerns the fractionation of wheat straw using steam explosion, coupled with ethanol extraction, and that this facilitates the establishment of sugars and lignin platform and enables the production of regenerated cellulose films.
  
  
  RESULTS
  The results showed that the hemicellulose fractionation yield was 73% under steam explosion at 1.6 MPa for 5.2 minutes, while the lignin fractionation yield was 90% by ethanol extraction at 160°C for 2 hours and with 60% ethanol (v/v). The cellulose yield reached up to 93% after steam explosion coupled with ethanol extraction. Therefore, cellulose sugar, hemicellulose sugar, and lignin platform were established effectively in the present study. Long fibers (retained by a 40-mesh screening) accounted for 90% of the total cellulose fibers, and the glucan conversion of short fibers was 90% at 9.0 hours with a cellulase loading of 25 filter paper units/g cellulose in enzymatic hydrolysis. Regenerated cellulose film was prepared from long fibers using [bmim]Cl, and the tensile strength and breaking elongation was 120 MPa and 4.8%, respectively. The cross-section of regenerated cellulose film prepared by [bmim]Cl displayed homogeneous structure, which indicated a dense architecture and a better mechanical performance.
  
  
  CONCLUSIONS
  Multilevel composition fractionation process using steam explosion followed by ethanol extraction was shown to be an effective process by which wheat straw could be fractionated into different polymeric fractions with high yields. High-value utilization of wheat straw cellulose was achieved by preparing regenerated cellulose film using [bmim]Cl.
authors.affiliation: State Key Laboratory of Biochemical Engineering, Institute of Process Engineering, Chinese Academy of Sciences, No.1 Zhongguancun North Second Street, Haidian District Beijing, 100190 PR China.
authors.forename: Hong-Zhang
authors.initials: HZ
authors.lastname: Chen
authors.affiliation: State Key Laboratory of Biochemical Engineering, Institute of Process Engineering, Chinese Academy of Sciences, No.1 Zhongguancun North Second Street, Haidian District Beijing, 100190 PR China ; University of Chinese Academy of Sciences, No.19A Yuquan Road, Shijingshan District Beijing, 100049 PR China.
authors.forename: Zhi-Hua
authors.initials: ZH
authors.lastname: Liu
keywords: Ethanol extraction; High-value utilization; Ionic liquid; Long fibers; Multilevel composition fractionation process; Regenerated cellulose film; Short fibers; Steam explosion; Wheat straw biomass