Assessing the molecular structure basis for biomass recalcitrance during dilute acid and hydrothermal pretreatments

These results suggest that there could be a balance between lignin removal and a need to retain some lignin and remain cell wall architecture with minimum alteration/ degradation of polysaccharides to provide an optimal pretreated biomass for subsequent enzymatic deconstruction

Yunqiao Pu; Fan Hu; Fang Huang; Brian H Davison; Arthur J Ragauskas


Scholarcy highlights

  • With the increasing concerns on diminishing fossil fuel resources, climate change and energy security, the utilization of renewable and sustainable resources for the production of fuels, chemicals and materials has become a global research theme and in the future will play an important role in our energy portfolio
  • Summary and conclusions In summary, dilute acid and hydrothermal pretreatments lead to substantial structural changes of lignin, hemicellulose and cellulose in lignocellulosic biomass
  • Β-O-4 cleavage, shift of S/G ratio, hemicellulose removal, changes in cellulose degree of polymerization and crystallinity, as well as porosity are among the most significant structural alterations observed in pretreated biomass
  • Given the rigid and complex spatial cell wall structure constructed by intimate linking of its chemical compositions, interactive effects naturally exist between these factors and altering one structural feature is accompanied by change of additional ones during dilute acid and hydrothermal pretreatments
  • It appears that there is no signal, independent chemical or structural factor that exclusively controls biomass recalcitrance. This observation may well be due to the fact that biomass accessibility to deconstruction enzymes is a key controlling factor which in turn can be influenced by the chemical compositional components described above
  • Samuel et al observed a ~20% lower number-average molecular weight in lignin in the dilute acid pretreated switchgrass at 190°C, which was attributed to the short pretreatment time and limited opportunities for recondensation
  • This issue needs to be further explored and defined in the upcoming years to provide a firm foundation by which pretreatment and biological deconstruction can be rationally optimized from first principles

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