The Study On Difference In Substrate Characteristics And Enzymatic Hydrolysis Performance Of Different Plant Biomass Under Pretreatment Of Fe³⁺Coupling With Dilute Sulfuric Acid

Nowadays,with the energy shortage and environment pollution problems exacerbating,developing new and sustainable energy is obviously pressing.Second generation bioethanol can effectively alleviate this worry,thus bioethanol study has received a lot of attention.For the naturally recalcitrant structure of lignocellulose,pretreatment becomes essential for lignocelluloses's utilization.Different biomass feedstock own different compositional contents and framework,they have various response to a same pretreatment,therefore,the selection of specific pretreatment method and corresponding conditions according to the properties of a specific feedstock has great significance in view of cost-effective utilization of resources.Diluted sulfuric acid pretreatment is considered as the most suitable pretreatment which is closest to practical production,and some studies have proved that several metal ions pretreatment can promote the final effect of pretreatment.Thus a combination of metal ions and sulfuric acid will favor pretreatment effect as well as the study for action mechanism of metal ions.This paper investigated the effect of ferric ion pretreatment coupling with sulfuric acid on three types of lignocellulose,i.e.Eichhornia crassipes(or water hyacinth),sugarcane bagasse and metasequoia sawdust.In the experiment,sulfuric acid pretreatment is set as comparison group with Fe3+ additive amount,acid concentration and temperature being independent variables.After analyzing the compositional contents,chemical structure and enzymatic hydrolysis properties of the feedstock before and after pretreatment,proper pretreatment parameters are determined.Through analysis of the differences in responce of three types of feedstock to this coupled pretreatment,function of Fe3+ is supposed to be determined.The main results are displayed as follow:(1)The best conditions of Fe3+ coupling with sulfuric acid pretreatment were Fe3+concentration of 0.1 mol/L,sulfuric acid of 2%(w/v)and temperature of 120?Under these conditions,1 g feedstock were soaked(pretreated)in 10 ml solution for 30 minutes.Then the pretreated feedstock was hydrolyzed with 30 FPU/g cellulase for 72 h,and the final sugar conversion was 78.11%.(2)Fe3+ coupling with dilute sulfuric acid pretreatment is suitable for Eichhornia crassipes,the pretreatment effect is not ideal for sugarcane bagasse and minimum for metasequoia sawdust.Under the optimal pretreatment conditions,the sugar yield of sugarcane bagasse was 29.18%,but it,s only 1.19%for Metasequoia sawdust.After pretreatment with Fe3+,the sugar conversion of Eichhornia crassipes and sugarcane bagasse after enzymatic hydrolysis for 72 h increased by 12.90%and 19.65%,respectively,compared with the single treatment of dilute sulfuric acid.(3)In the Fe3+ coupling with dilute sulfuric acid pretreatment,the main components removed from Eichhornia crassipes were hemicellulose and ash.The removal rate of the hemicellulose and ash were up to 92.89%and 82.70%,respectively,under the optimum pretreatment conditions.Lignin removal was less,and the removal rate of cellulose was almost zero.In terms of sugarcane bagasse,the removal rates of hemicelluloses,lignin and ash reached a high level,which were 94.99%,41.05%and 87.24%,respectively,under the optimal pretreatment conditions.And the removal rate of cellulose was 19.49%.Fe3+ has a different effect on Eichhornia crassipes and sugarcane bagasse.Ferc could increase the accessibility of enzyme to Eichhornia crassipes by promoting the removal of hemicellulose and ash.Fe3+ is synergistic with dilute sulfuric acid.For sugarcane bagasse,Fe3+ may act on the cellulose,destroying its chemical or physical structure,increasing the accessibility of enzyme to sugarcane bagasse.