The Effect Of Aqueous Ammonia Pretreatment On Components And Structure Of Cell Wall From Sugar Beet Pulp

Cellulosic ethanol is a clean and renewable energy.Sugar beet pulp(SBP)is an ideal biomass for the ethanol production,but the low efficiency in enzymatic hydrolysis of cellulose restricts its industrial utilization.Hence,pretreatment is the key element in the ethanol production from SBP to destroy the recalcitrance of cell wall for improved enzymatic hydrolysis.In our previous study,aqueous ammonia has been used to pretreat SBP,yet the synergetic mechanism of the pretreatment on SBP should be studied further.In this paper,the effects of aqueous ammonia pretreatment on chemical composition and physical structure of SBP were analyzed by various chemical analysis and micro-imaging techniques at cell wall level.The relationship between physicochemical variation and enzymatic hydrolysis of cellulose was also discussed.This research will provide theory and technical support for ethanol production from SBP.The main results are as follows:Aqueous ammonia pretreatment changed the chemical composition of the cell wall of SBP.The contents of hemicellulose lipid wax,lignin and pectin were reduced,yet cellulose content was increased.The distribution of lignin was changed.Thecellulose was exposed and its degree of polymerization was decreased.Aqueous ammonia pretreatment changed the macroscopic morphology and structural characteristics,such as the increase in pore size and volume.The changes of macroscopic morphology and composition leaded to the changes of microscopic morphology such as the cell wall breakage,reduced sediments,irregular cell morphology,and vascular bundle fracture.The variation of physicochemical structure of cell wall improved the adsorption of substrate with cellulase,and increased the yield of reducing sugar.The yield of reducing sugar was as high as 481.02 mg/g after treatment at 80°C,which was 2.24 times higher than that of the control.Aqueous ammonia pretreatment could change the content and distribution of chemical components of cell wall of SBP residue under mild conditions,destroy the cell wall structure,and significantly increase the enzymatic hydrolysis efficiency of cellulose,which is an ideal pretreatment process.