Bioconversion of lignocellulosic biomass to ethanol is significantly hindered by the structural and chemical complexity of biomass,which makes these materials a challenge to be used as feedstocks for cellulosic ethano...Bioconversion of lignocellulosic biomass to ethanol is significantly hindered by the structural and chemical complexity of biomass,which makes these materials a challenge to be used as feedstocks for cellulosic ethanol production.Cellulose and hemicellulose,when hydrolyzed into their component sugars,can be converted into ethanol through well established fermentation technologies.However,sugars necessary for fermentation are trapped inside the crosslinking structure of the lignocellulose.Hence,pretreatment of biomass is always necessary to remove and/or modify the surrounding matrix of lignin and hemicellulose prior to the enzymatic hydrolysis of the polysaccharides(cellulose and hemicellulose)in the biomass.Pretreatment refers to a process that converts lignocellulosic biomass from its native form,in which it is recalcitrant to cellulase enzyme systems,into a form for which cellulose hydrolysis is much more effective.In general,pretreatment methods can be classified into three categories,including physical,chemical,and biological pretreatment.The subject of this paper emphasizes the biomass pretreatment in preparation for enzymatic hydrolysis and microbial fermentation for cellulosic ethanol production.It primarily covers the impact of biomass structural and compositional features on the pretreatment,the characteristics of different pretreatment methods,the pretreatment study status,challenges,and future research targets.展开更多
Pretreatment is one of the most important unit operations for ethanol production from biomass feedstocks.In this study,corn stover was used as a feedstock to examine the effectiveness of two pretreatments:electrolyzed...Pretreatment is one of the most important unit operations for ethanol production from biomass feedstocks.In this study,corn stover was used as a feedstock to examine the effectiveness of two pretreatments:electrolyzed water pretreatment and a two-step pretreatment.Electrolyzed water was employed as a catalyst to conduct one-step pretreatment of corn stover at three temperatures(165,180 and 195°C) and three treatment times(10,20 and 30 min).During the two-step pretreatment process,an organic alkaline solution of 1%(w/w) NaOH in 70%(w/w) ethanol was used for lignin removal in the first step,followed by a second step using hot water.No furfural or 5-hydroxymethyl furfural was detected in the hydrolysates from both pretreatment methods when the detection limit of the HPLC was 0.2 g/L.The highest glucan conversion yields were 83% obtained at 195°C for 30 min with acidic electrolyzed water and 83% by the two-step process,where the second step of the pretreatment was at 135°C for 30 min.The hydrolyzates from the two pretreatment methods showed good performance in Saccharomyces cerevisiae fermentation tests.The two new methods may provide promising alternatives for the pretreatment of biomass for ethanol production.展开更多
The aim of the study was to evaluate,from an economic standpoint,the feasibility of using sugar beet pulp(SBP)as the feedstock in an existing sugar processing plant to ethanol.Two base cases were studied.Case 1 incorp...The aim of the study was to evaluate,from an economic standpoint,the feasibility of using sugar beet pulp(SBP)as the feedstock in an existing sugar processing plant to ethanol.Two base cases were studied.Case 1 incorporated dilute sulfuric acid pretreatment,enzymatic hydrolysis,and fermentation using S.cervisiae.Case 2 neglected the pretreatment step and used a series of enzymes in Simultaneous Saccharification and Fermentation(SSF)with S.cervisiae yeast followed by E.coli K011 fermentation.The ethanol production cost for each case was estimated to be$1.50 and$1.10 per gallon of ethanol for case 1 and case 2,respectively.Assuming a 10%discount rate,a minimum selling price of$2.35 per gallon was obtained for case 1 and$1.53 per gallon for case 2.These prices can be competitive with the increasing gasoline prices.However,base case 2 has higher potential to be feasible with the discovery of efficient microbial species.展开更多
文摘Bioconversion of lignocellulosic biomass to ethanol is significantly hindered by the structural and chemical complexity of biomass,which makes these materials a challenge to be used as feedstocks for cellulosic ethanol production.Cellulose and hemicellulose,when hydrolyzed into their component sugars,can be converted into ethanol through well established fermentation technologies.However,sugars necessary for fermentation are trapped inside the crosslinking structure of the lignocellulose.Hence,pretreatment of biomass is always necessary to remove and/or modify the surrounding matrix of lignin and hemicellulose prior to the enzymatic hydrolysis of the polysaccharides(cellulose and hemicellulose)in the biomass.Pretreatment refers to a process that converts lignocellulosic biomass from its native form,in which it is recalcitrant to cellulase enzyme systems,into a form for which cellulose hydrolysis is much more effective.In general,pretreatment methods can be classified into three categories,including physical,chemical,and biological pretreatment.The subject of this paper emphasizes the biomass pretreatment in preparation for enzymatic hydrolysis and microbial fermentation for cellulosic ethanol production.It primarily covers the impact of biomass structural and compositional features on the pretreatment,the characteristics of different pretreatment methods,the pretreatment study status,challenges,and future research targets.
基金supported by China Scholarship Council with a two-year fellowship to study in University of Illinois at Urbana & Champaign
文摘Pretreatment is one of the most important unit operations for ethanol production from biomass feedstocks.In this study,corn stover was used as a feedstock to examine the effectiveness of two pretreatments:electrolyzed water pretreatment and a two-step pretreatment.Electrolyzed water was employed as a catalyst to conduct one-step pretreatment of corn stover at three temperatures(165,180 and 195°C) and three treatment times(10,20 and 30 min).During the two-step pretreatment process,an organic alkaline solution of 1%(w/w) NaOH in 70%(w/w) ethanol was used for lignin removal in the first step,followed by a second step using hot water.No furfural or 5-hydroxymethyl furfural was detected in the hydrolysates from both pretreatment methods when the detection limit of the HPLC was 0.2 g/L.The highest glucan conversion yields were 83% obtained at 195°C for 30 min with acidic electrolyzed water and 83% by the two-step process,where the second step of the pretreatment was at 135°C for 30 min.The hydrolyzates from the two pretreatment methods showed good performance in Saccharomyces cerevisiae fermentation tests.The two new methods may provide promising alternatives for the pretreatment of biomass for ethanol production.
基金We thank Dr.Scott Pryor and Rachel Rorick at the North Dakota State University for allowing us to use their results in this work.We thank Dr.Mike Mann and Dr.Robert Wills at the University of North Dakota for their help in reviewing this paper.We also thank the American Crystal Sugar Company(East Grand Forks,MN 56721)for providing us with the SBPand Genencor(Palo Alto,CA 94304)for providing us all the enzymes.Lastly,we acknowledge North Dakota EPSCoR for funding the project.
文摘The aim of the study was to evaluate,from an economic standpoint,the feasibility of using sugar beet pulp(SBP)as the feedstock in an existing sugar processing plant to ethanol.Two base cases were studied.Case 1 incorporated dilute sulfuric acid pretreatment,enzymatic hydrolysis,and fermentation using S.cervisiae.Case 2 neglected the pretreatment step and used a series of enzymes in Simultaneous Saccharification and Fermentation(SSF)with S.cervisiae yeast followed by E.coli K011 fermentation.The ethanol production cost for each case was estimated to be$1.50 and$1.10 per gallon of ethanol for case 1 and case 2,respectively.Assuming a 10%discount rate,a minimum selling price of$2.35 per gallon was obtained for case 1 and$1.53 per gallon for case 2.These prices can be competitive with the increasing gasoline prices.However,base case 2 has higher potential to be feasible with the discovery of efficient microbial species.
