Biology Structure And Lignin Distribution Of Pennisetum Sinese

Biomass fiber resource is a rich renewable resource,and can be used to produce pulp,fiber,biofuel,biomass based chemicals,etc.The complex chemical structure of the fiber cell wall impeded the efficient utilization of fiber resources.Pretreatment techniques are needed to disrupt the chemical structure of the fiber cell walls in order to obtain efficient conversion of fiber resources.Pennisetum Sinese is imported from abroad and is one kind fungus grass with top quality and high production.It is tall and resistant to stress,has high contents of crude protein and sugar.In the present work,Pennisetum Sinese was selected as the research object,the biological structure,cell wall ultrastructure and lignin distributions in cell walls of Pennisetum Sinese were investigated by using microscopic spectroscopy.Further effect of ionic liquid pretreatment on cell wall microstructure and lignin distribution changes was analyzed,which can provide a theoretical guide for the efficient conversion and rational utilization of Pennisetum Sinese.Light microscopy(LM)and transmission electron microscopy(TEM)were used to observe the anatomy and ultrastructure of the Pennisetum sinese,confocal Raman microscopy(CRM)method was performed to explore the local distribution of lignin chemistry.The results showed that there were many types of Pennisetum Sinese cells,and each type of cell had a specific size,shape,location,and property of the cell wall.The content of lignin in sclerenchyma cells of the vascular and epidermal cell was higher than that in parenchyma cells.Higher lignin concentration was observed in compound middle lamella(CML)and cell corner(CC).Quantitative analysis alkaline nitrobenzene oxidation revealed that lignin of Pennisetum Sinese was typical GSH-type lignin.It was observed that the highest content of hydroxyl groups was aliphatic OH(3.96 mmol/g),and non-condensed phenolic hydroxyl accounted for a large proportion content of the total phenolic hydroxyl(96.3%).In addition,2D-HSQC NMR analysis indicated that the alkyl aryl ether linkages was predominant(?-O-4',84.4% of total linkages),followed by resinols(?-?',9.9%)and phenylcomumarans(?-5',5.7%).The changes in delignification capacity of different plant cell walls,the morphological and chemical characteristics and enzymatic properties during pretreated with different proportions of cholinium lysine ionic liquid([Ch][Lys] IL)-water solution at 90°C were also investigated.Light microscopy(LM)observation revealed that thedynamic morphology changes,especially for the significantly swelling was observed in sclerenchyma cells,the parenchyma cells were apparently collapsed on the lumen side and many cells were crushed and the surface become rough and porous.CRM analysis indicated that the reduction of lignin intensity in CC and CML were more than that in the S2 layer after various contents IL pretreated for 10 min.The delignification decreased significantly when the IL content was decreased from 75% to 25%,corresponding with the reduction in the concentration of hydroxycinnamic acids(HCA)which plays an important role in cross-linking into cohesive network.With the addition of proportions of green and cheap water,lignin extractability were not diminished significantly,the viscosity of ionic liquids greatly reduced and convenient experiment operated as well.The polysaccharides efficiency(>80% for glucose and >60% for xylose)was enhanced significantly,which approximately 4-fold increase in sugar yield over the native samples(22.2% for glucose and 17.0% for xylose).Statistical analysis revealed that the content of glucose in the recovered residues increased gradually form40.6% to 56.0%,with the increment of IL content to 75%.The relative increase in glucose was ascribed to the removal of lignin and partly dissolution of xylan,since the acid-insoluble lignin content decreased from 16.4% to 10.3% and the xylan content changed slightly.Interestingly,approximately 50% of lignin was recovered from the extracted lignin with the increasing IL content from 25% to 75%.During the 25% [Ch][Lys]-water solution pretreatment process,the level of delignification in cell wall of Pennisetum sinese increased with pretreatment time.Sclerenchyma cell wall area increases slightly,while lumen area of cells decreased slightly,swelling of cell wall occurred,and the Raman signal was significantly decreased,which means that the delignification process was severe.Interestingly,there was a preferential delignification in the CC and CML than that in the S2.Further extension of the pretreatment time,swelling of the cell wall became weak;lignin concentration in each region of cell wall was more homogeneous,When prolonging residence time to 60 min,cell wall lignin in all regions of the Raman signal strength improved slightly,indicating that during delignification process,the lignin has been part of the migration and deposition.