title: Biomass digestibility is predominantly affected by three factors of wall polymer features distinctive in wheat accessions and rice mutants.
abstract: BACKGROUND
  Wheat and rice are important food crops with enormous biomass residues for biofuels. However, lignocellulosic recalcitrance becomes a crucial factor on biomass process. Plant cell walls greatly determine biomass recalcitrance, thus it is essential to identify their key factors on lignocellulose saccharification. Despite it has been reported about cell wall factors on biomass digestions, little is known in wheat and rice. In this study, we analyzed nine typical pairs of wheat and rice samples that exhibited distinct cell wall compositions, and identified three major factors of wall polymer features that affected biomass digestibility.
  
  
  RESULTS
  Based on cell wall compositions, ten wheat accessions and three rice mutants were classified into three distinct groups each with three typical pairs. In terms of group I that displayed single wall polymer alternations in wheat, we found that three wall polymer levels (cellulose, hemicelluloses and lignin) each had a negative effect on biomass digestibility at similar rates under pretreatments of NaOH and H2SO4 with three concentrations. However, analysis of six pairs of wheat and rice samples in groups II and III that each exhibited a similar cell wall composition, indicated that three wall polymer levels were not the major factors on biomass saccharification. Furthermore, in-depth detection of the wall polymer features distinctive in rice mutants, demonstrated that biomass digestibility was remarkably affected either negatively by cellulose crystallinity (CrI) of raw biomass materials, or positively by both Ara substitution degree of non-KOH-extractable hemicelluloses (reverse Xyl/Ara) and p-coumaryl alcohol relative proportion of KOH-extractable lignin (H/G). Correlation analysis indicated that Ara substitution degree and H/G ratio negatively affected cellulose crystallinity for high biomass enzymatic digestion. It was also suggested to determine whether Ara and H monomer have an interlinking with cellulose chains in the future.
  
  
  CONCLUSIONS
  Using nine typical pairs of wheat and rice samples having distinct cell wall compositions and wide biomass saccharification, Ara substitution degree and monolignin H proportion have been revealed to be the dominant factors positively determining biomass digestibility upon various chemical pretreatments. The results demonstrated the potential of genetic modification of plant cell walls for high biomass saccharification in bioenergy crops.
authors.affiliation: National Key Laboratory of Crop Genetic Improvement, Huazhong Agricultural University, Wuhan 430070, China.|Biomass and Bioenergy Research Centre, Huazhong Agricultural University, Wuhan 430070, China.|College of Plant Sciences and Technology, Huazhong Agricultural University, Wuhan 430070, China.
authors.forename: Zhiliang
authors.initials: Z
authors.lastname: Wu
authors.affiliation: National Key Laboratory of Crop Genetic Improvement, Huazhong Agricultural University, Wuhan 430070, China.|Biomass and Bioenergy Research Centre, Huazhong Agricultural University, Wuhan 430070, China.|College of Plant Sciences and Technology, Huazhong Agricultural University, Wuhan 430070, China.
authors.forename: Mingliang
authors.initials: M
authors.lastname: Zhang
authors.affiliation: National Key Laboratory of Crop Genetic Improvement, Huazhong Agricultural University, Wuhan 430070, China.|Biomass and Bioenergy Research Centre, Huazhong Agricultural University, Wuhan 430070, China.|College of Plant Sciences and Technology, Huazhong Agricultural University, Wuhan 430070, China.
authors.forename: Lingqiang
authors.initials: L
authors.lastname: Wang
authors.affiliation: National Key Laboratory of Crop Genetic Improvement, Huazhong Agricultural University, Wuhan 430070, China.|Biomass and Bioenergy Research Centre, Huazhong Agricultural University, Wuhan 430070, China.|College of Plant Sciences and Technology, Huazhong Agricultural University, Wuhan 430070, China.
authors.forename: Yuanyuan
authors.initials: Y
authors.lastname: Tu
authors.affiliation: National Key Laboratory of Crop Genetic Improvement, Huazhong Agricultural University, Wuhan 430070, China.|Biomass and Bioenergy Research Centre, Huazhong Agricultural University, Wuhan 430070, China.|College of Plant Sciences and Technology, Huazhong Agricultural University, Wuhan 430070, China.
authors.forename: Jing
authors.initials: J
authors.lastname: Zhang
authors.affiliation: National Key Laboratory of Crop Genetic Improvement, Huazhong Agricultural University, Wuhan 430070, China.|Biomass and Bioenergy Research Centre, Huazhong Agricultural University, Wuhan 430070, China.|College of Plant Sciences and Technology, Huazhong Agricultural University, Wuhan 430070, China.
authors.forename: Guosheng
authors.initials: G
authors.lastname: Xie
authors.affiliation: National Key Laboratory of Crop Genetic Improvement, Huazhong Agricultural University, Wuhan 430070, China.|Biomass and Bioenergy Research Centre, Huazhong Agricultural University, Wuhan 430070, China.|College of Plant Sciences and Technology, Huazhong Agricultural University, Wuhan 430070, China.
authors.forename: Weihua
authors.initials: W
authors.lastname: Zou
authors.affiliation: National Key Laboratory of Crop Genetic Improvement, Huazhong Agricultural University, Wuhan 430070, China.|Biomass and Bioenergy Research Centre, Huazhong Agricultural University, Wuhan 430070, China.|College of Plant Sciences and Technology, Huazhong Agricultural University, Wuhan 430070, China.
authors.forename: Fengcheng
authors.initials: F
authors.lastname: Li
authors.affiliation: National Key Laboratory of Crop Genetic Improvement, Huazhong Agricultural University, Wuhan 430070, China.|Biomass and Bioenergy Research Centre, Huazhong Agricultural University, Wuhan 430070, China.|College of Life Sciences and Technology, Huazhong Agricultural University, Wuhan 430070, China.
authors.forename: Kai
authors.initials: K
authors.lastname: Guo
authors.affiliation: National Key Laboratory of Crop Genetic Improvement, Huazhong Agricultural University, Wuhan 430070, China.|Biomass and Bioenergy Research Centre, Huazhong Agricultural University, Wuhan 430070, China.|College of Sciences, Huazhong Agricultural University, Wuhan 430070, China.
authors.forename: Qing
authors.initials: Q
authors.lastname: Li
authors.affiliation: Institute of Food Crops, Hubei Academy of Agricultural Sciences, Wuhan 430064, China.
authors.forename: Chunbao
authors.initials: C
authors.lastname: Gao
authors.affiliation: National Key Laboratory of Crop Genetic Improvement, Huazhong Agricultural University, Wuhan 430070, China.|Biomass and Bioenergy Research Centre, Huazhong Agricultural University, Wuhan 430070, China.|College of Plant Sciences and Technology, Huazhong Agricultural University, Wuhan 430070, China.
authors.forename: Liangcai
authors.initials: L
authors.lastname: Peng