液氨和过氧化氢预处理对稻草酶解效果的影响机制
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摘要
稻草是一种重要的木质纤维素资源,可以作为纤维素乙醇转化的原料。该试验通过高温过氧化氢(高温HP)、低温过氧化氢(低温HP)和液氨预处理(liquid ammonia treatment,LAT)3种预处理方式来克服生物质原料的酶解顽抗性,促进稻草酶解转化为可发酵单糖。对预处理后的稻草进行酶解试验,利用高效液相色谱法(highperformanceliquid chromatography,HPLC)定量测定了酶解液中的单糖含量,通过酶解转化率和单糖产量对预处理效果进行了分析比较。试验结果表明高温HP、低温HP和LAT 3种预处理方式均有效提升酶解率,其中LAT预处理的酶解促进作用效果最佳,高温HP预处理次之。稻草在120℃、预处理时间为60 min、30%H2O2水溶液与原料质量比为0.75∶1的高温HP预处理下,在纤维素酶添加量为15U/g时葡聚糖和木聚糖的酶解率分别为61.55%和47.82%,每千克干基稻草原料经144h酶解可生产单糖334.5 g。稻草在90℃、含水率60%、驻留时间为5 min、液氨与原料比例为1∶1的LAT预处理下,在纤维素酶添加量为15 U/g时,葡聚糖和木聚糖的72 h酶解率分别为88.62%和79.29%,每千克干基稻草原料经144 h酶解可生产单糖554.1 g,是未处理原料的2.9倍,总糖回收率达到90%。综上所述,LAT预处理稻草的酶解率显著高于其他单一预处理方法,该研究结果可为稻草制取燃料乙醇提供基础数据。
Biomass is a promising, eco-friendly, and renewable source for generating energy, fuels, and bio-chemicals that could partially replace fossil fuels to reduce the pressure of environmental pollution problems. Rice straw is one of the most important lignocellulosic biomass in China, which is a potential feedstock to produce bio-ethanol by enzyme hydrolysis method. The production process of bio-ethanol is composed of three stages, namely pretreatment, enzymatic hydrolysis, and fermentation. The pretreatment process is important step to overcome biomass recalcitrance, and improve the performance of enzymatic hydrolysis. In this study, three types of pretreated method, namely high-temperature hydrogen peroxide pretreatment(HTHP), low-temperature hydrogen peroxide pretreatment(LTHP), and liquid ammonia pretreatment(LAT), were used to overcome biomass recalcitrance and improve the performance of enzymatic hydrolysis. Then, a caparison of the performance of enzymatic hydrolysis and the yield of monosaccharides were carried out by using three pretreatment methods. The contents of monosaccharide(glucose, xylose, and arabinose) of the enzymatic hydrolysate were quantitative determined by high performance liquid chromatography(HPLC). Results showed that three pretreatment methods were effective to enhance the performance of enzymatic hydrolysis, and ordered as LAT > HTHP > LTHP. Based on the chemical component analysis before and after pretreatment, the content of glucan decreased from 35.54% of control sample to 33.76% of HTHP pretreatment, 35.12% of LTHP pretreatment, and 35.86% of LAT pretreatment. The content of xylan decreased from 19.06% of control sample to 14.69% of HTHP pretreatment, 17.53% of LTHP pretreatment, while increase to 19.07% of LAT pretreatment. The optimal pretreatment conditions of HTHP were 120 ℃, mass ratio of 0.75:1(w/w) between 30% H_2O_2 solution and biomass ratio, and 60 minutes' residence time. The conversion rates of glucan and xylan were 61.55% and 47.82%, respectively, after 72 hours enzymatic hydrolysis at 1% glucan loading using 15 FPU/(g of glucan) of cellulase. The sugar yield was 334.5 g per kg of rice straw(dry basis) after 144 hours enzymatic hydrolysis. The effect of H_2O_2 addition on the enzymatic hydrolysis effect was significant, and the excessive addition amount(more than 1.0:1) led to a rapid decrease in the enzymatic hydrolysis rate. The optimal pretreatment conditions of LAT were 90 ℃, mass ratio of 1:1(w/w) between liquid ammonia and biomass ratio, 60% moisture content(drybasis) and 5 minutes' residence time. The conversion rates of glucan and xylan were 88.62% and 79.29%, respectively, after 72 hours enzymatic hydrolysis at 1% glucan loading using 15 FPU/(g of glucan) of cellulase. The sugar yield was 554.1 g per kg of dry rice straw after 144 hours enzymatic hydrolysis, which is 2.9-fold of producing from untreated straw. The total sugar recovery rate was almost 90%. In conclusion, the performance of LAT pretreatment was more effective than other two pretreatment methods(HTHP and LTHP). This study would be useful to supply scientific and basic data for industrial application of rice straw.
Biomass is a promising, eco-friendly, and renewable source for generating energy, fuels, and bio-chemicals that could partially replace fossil fuels to reduce the pressure of environmental pollution problems. Rice straw is one of the most important lignocellulosic biomass in China, which is a potential feedstock to produce bio-ethanol by enzyme hydrolysis method. The production process of bio-ethanol is composed of three stages, namely pretreatment, enzymatic hydrolysis, and fermentation. The pretreatment process is important step to overcome biomass recalcitrance, and improve the performance of enzymatic hydrolysis. In this study, three types of pretreated method, namely high-temperature hydrogen peroxide pretreatment(HTHP), low-temperature hydrogen peroxide pretreatment(LTHP), and liquid ammonia pretreatment(LAT), were used to overcome biomass recalcitrance and improve the performance of enzymatic hydrolysis. Then, a caparison of the performance of enzymatic hydrolysis and the yield of monosaccharides were carried out by using three pretreatment methods. The contents of monosaccharide(glucose, xylose, and arabinose) of the enzymatic hydrolysate were quantitative determined by high performance liquid chromatography(HPLC). Results showed that three pretreatment methods were effective to enhance the performance of enzymatic hydrolysis, and ordered as LAT > HTHP > LTHP. Based on the chemical component analysis before and after pretreatment, the content of glucan decreased from 35.54% of control sample to 33.76% of HTHP pretreatment, 35.12% of LTHP pretreatment, and 35.86% of LAT pretreatment. The content of xylan decreased from 19.06% of control sample to 14.69% of HTHP pretreatment, 17.53% of LTHP pretreatment, while increase to 19.07% of LAT pretreatment. The optimal pretreatment conditions of HTHP were 120 ℃, mass ratio of 0.75:1(w/w) between 30% H_2O_2 solution and biomass ratio, and 60 minutes' residence time. The conversion rates of glucan and xylan were 61.55% and 47.82%, respectively, after 72 hours enzymatic hydrolysis at 1% glucan loading using 15 FPU/(g of glucan) of cellulase. The sugar yield was 334.5 g per kg of rice straw(dry basis) after 144 hours enzymatic hydrolysis. The effect of H_2O_2 addition on the enzymatic hydrolysis effect was significant, and the excessive addition amount(more than 1.0:1) led to a rapid decrease in the enzymatic hydrolysis rate. The optimal pretreatment conditions of LAT were 90 ℃, mass ratio of 1:1(w/w) between liquid ammonia and biomass ratio, 60% moisture content(drybasis) and 5 minutes' residence time. The conversion rates of glucan and xylan were 88.62% and 79.29%, respectively, after 72 hours enzymatic hydrolysis at 1% glucan loading using 15 FPU/(g of glucan) of cellulase. The sugar yield was 554.1 g per kg of dry rice straw after 144 hours enzymatic hydrolysis, which is 2.9-fold of producing from untreated straw. The total sugar recovery rate was almost 90%. In conclusion, the performance of LAT pretreatment was more effective than other two pretreatment methods(HTHP and LTHP). This study would be useful to supply scientific and basic data for industrial application of rice straw.
引文
[1]Zhao C,Shao Q J,Ma Z Q,et al.Physical and chemical characterizations of corn stalk resulting from hydrogen peroxide presoaking prior to ammonia fiber expansion pretreatment[J].Industrial Crops and Products,2016,83:86-93.
[2]吴丹焱,辛善志,刘标,等.基于木质素部分脱除及其含量对生物质热解特性的影响[J].农业工程学报,2018,34(1):193-197.Wu Danyan,Xin Shanzhi,Liu Biao,et al.Influence of lignin content on pyrolysis characteristics ofbiomass based on part of lignin removal[J].Transactions of the Chinese Society of Agricultural Engineering(Transactions of the CSAE),2018,34(1):193-197.(in Chinese with English abstract)
[3]Blummel M,Teymouri F,Moore J,et al.Ammonia fiber expansion(AFEX)as spin off technology from 2nd generation biofuel for upgrading cereal straws and stovers for livestock feed[J].Animal Feed Science and Technology,2018,236:178-186.
[4]Yu H,Guo J,Chen Y F,et al.Efficient utilization of hemicellulose and cellulose in alkali liquor-pretreated corncob for bioethanol production at high solid loading by Spathaspora passalidarum U1-58[J].Bioresource Technology2017,232:168-175.
[5]Amiri H,Karimi K,Zilouei H.Organosolv pretreatment of rice straw for efficient acetone,butanol,and ethanol production[J].Bioresource Technology,2014,152:450-456.
[6]刘晓永,李书田.中国秸秆养分资源及还田的时空分布特征[J].农业工程学报,2017,33(21):1-19.Liu Xiaoyong,Li Shutian.Temporal and spatial distribution characteristics of crop straw nutrient resources and returning to farmland in China[J].Transactions of the Chinese Society for Agricultural Engineering(Transactions of the CSAE),2017,33(21):1-19.(in Chinese with English abstract)
[7]Zhu S D,Huang W J,Huang W X,et al.Pretreatment of rice straw for ethanol production by a two-step process using dilute sulfuric acid and sulfomethylation reagent[J].Applied Energy,2015,145:190-196.
[8]Kim I,Lee B,Song D S,et al.Effects of ammonium carbonate pretreatment on the enzymatic digestibility and structural features of rice straw[J].Bioresource Technology2014,166:353-357.
[9]Domanski J,Borowski S,Marchut-Mikolajczyk O,et al Pretreatment of rye straw with aqueous ammonia for conversion to fermentable sugars as a potential substrates in biotechnological processes[J].Biomass&Bioenergy,2016,91:91-97.
[10]Antonopoulou G,Jonuzaj S,Gavala H N,et al.The effect of aqueous ammonia soaking pretreatment on methane generation uing different lignocellulosic feedstocks[J].Waste&Biomass Valorization,2015,6(3):281-291.
[11]Ngamprasertsith S,Sunphorka S,Kuchonthara P,et al.Pretreatment of rice straw by hot-compressed water for enzymatic saccharification[J].Korean Journal of Chemical Engineering,2015,32(10):2007-2013.
[12]刘翀,张瑞婷,刘本国,等.蒸汽爆破处理对麦麸的酚酸组成及其抗氧化活性的影响[J].农业工程学报,201632(6):308-314.Liu Chong,Zhang Ruiting,Liu Benguo,et al.Effect of steam explosion treatment on phenolic acid compositionof wheat bran and its antioxidant capacity[J].Transactions of the Chinese Society of Agricultural Engineering(Transactions of the CSAE),2016,32(6):308-314.(in Chinese with English abstract)
[13]马欢,刘伟伟,刘萍,等.微波预处理对水稻秸秆糖化率与成分和结构的影响[J].农业机械学报,2014,45(10):180-186.MaHuan,LiuWeiwei,Liu Ping,et al.Effects of microwave pretreatment on enzymatic saccharification and lignocellulosic structure of rice straw[J].Transactions of the Chinese Society of Agricultural Machinery,2014,45(10):180-186.(in Chinese with English abstract)
[14]Zhong C,Lau M W,Balan V,et al.Optimization of enzymatic hydrolysis and ethanol fermentation from AFEX-treated rice straw[J].Applied Microbiology and Biotechnology,2009,84(4):667-676.
[15]Hou X D,Smith T J,Li N,et al.Novel renewable ionic liquids as highly effective solvents for pretreatment of rice straw biomass by selective removal of lignin[J].Biotechnology and Bioengineering,2012,109(10):2484-2493.
[16]Yang L F,Cao J,Mao J Y,et al.Sodium carbonate-sodium sulfite pretreatment for improving the enzymatic hydrolysis of rice straw[J].Industrial Crops and Products,2013,43:711-717.
[17]Garlock R J,Balan V,Dale B E,et al.Comparative material balances around pretreatment technologies for the conversion of switchgrass to soluble sugars[J].Bioresource Technology2011,102(24):11063-11071.
[18]Nguyen T A,Kim K R,Han S J,et al.Pretreatment of rice straw with ammonia and ionic liquid for lignocellulose conversion to fermentable sugars[J].Bioresource Technology2010,101(19):7432-7438.
[19]Kumar R,Mago G,Balan V,et al.Physical and chemical characterizations of corn stover and poplar solids resulting from leading pretreatment technologies[J].Bioresource Technology,2009,100(17):3948-3962.
[20]Nissila M E,Lay C,Puhakka J A,et al.Dark fermentative hydrogen production from lignocellulosic hydrolyzates-Areview[J].Biomass&Bioenergy,2014,67:145-159.
[21]Zhao C,Ma Z Q,Shao Q J,et al.Enzymatic hydrolysis and physiochemical characterization of corn leaf after H-AFEXpretreatment[J].Energy&Fuels,2016,30(2):1154-1161.
[22]Umagiliyage A L,Choudhary R,Liang Y,et al.Laboratory scale optimization of alkali pretreatment for improving enzymatic hydrolysis of sweet sorghum bagasse[J].Industrial Crops and Products,2015,74:977-986.
[23]Shao Q,Chundawat S P,Krishnan C,et al.Enzymatic digestibility and ethanol fermentability of AFEX-treated starch-rich lignocellulosics such as corn silage and whole corn plant[J].Biotechnology for Biofuels,2010,3(1):12.
[24]Li Q M,Li X J,Jiang Y L,et al.Analysis of degradation products and structural characterization of giant reed and Chinese silvergrass pretreated by 60Co-γirradiation[J].Industrial Crops and Products,2016,83:307-315.
[25]Garlock R J,Balan V,Dale B E.Optimization of AFEX?pretreatment conditions and enzyme mixtures to maximize sugar release from upland and lowland switchgrass[J].Bioresource Technology,2012,104:757-768.
[26]Rabelo S C,Andrade R R,Maciel Filho R,et al.Alkaline hydrogen peroxide pretreatment,enzymatic hydrolysis and fermentation of sugarcane bagasse to ethanol[J].Fuel,2014,136:349-357.
[27]Gao M T,Yano S,Inoue H,et al.Combination of wet disk milling and hydrogen peroxide treatments for enhancing saccharification of sugarcane bagasse[J].Biochemical Engineering Journal,2012,68:152-158.
[28]赵相君.农作物秸秆液氨-过氧化氢预处理参数优化及酶解效果研究[D].杭州:浙江农林大学,2013.
[29]Singh R,Tiwari S,Srivastava M,et al.Experimental study on the performance of microwave assisted Hydrogen peroxide(H2O2)pretreatment of rice straw[J].Agricultural Engineering International:The CIGR Journal,2014,16(1):173-181.
[30]Zhao C,Cao Y,Ma Z Q,et al.Optimization of liquid ammonia pretreatment conditions for maximizing sugar release from giant reed(Arundo donax L.)[J].Biomass&Bioenergy,2017,98(2):61-69.
[2]吴丹焱,辛善志,刘标,等.基于木质素部分脱除及其含量对生物质热解特性的影响[J].农业工程学报,2018,34(1):193-197.Wu Danyan,Xin Shanzhi,Liu Biao,et al.Influence of lignin content on pyrolysis characteristics ofbiomass based on part of lignin removal[J].Transactions of the Chinese Society of Agricultural Engineering(Transactions of the CSAE),2018,34(1):193-197.(in Chinese with English abstract)
[3]Blummel M,Teymouri F,Moore J,et al.Ammonia fiber expansion(AFEX)as spin off technology from 2nd generation biofuel for upgrading cereal straws and stovers for livestock feed[J].Animal Feed Science and Technology,2018,236:178-186.
[4]Yu H,Guo J,Chen Y F,et al.Efficient utilization of hemicellulose and cellulose in alkali liquor-pretreated corncob for bioethanol production at high solid loading by Spathaspora passalidarum U1-58[J].Bioresource Technology2017,232:168-175.
[5]Amiri H,Karimi K,Zilouei H.Organosolv pretreatment of rice straw for efficient acetone,butanol,and ethanol production[J].Bioresource Technology,2014,152:450-456.
[6]刘晓永,李书田.中国秸秆养分资源及还田的时空分布特征[J].农业工程学报,2017,33(21):1-19.Liu Xiaoyong,Li Shutian.Temporal and spatial distribution characteristics of crop straw nutrient resources and returning to farmland in China[J].Transactions of the Chinese Society for Agricultural Engineering(Transactions of the CSAE),2017,33(21):1-19.(in Chinese with English abstract)
[7]Zhu S D,Huang W J,Huang W X,et al.Pretreatment of rice straw for ethanol production by a two-step process using dilute sulfuric acid and sulfomethylation reagent[J].Applied Energy,2015,145:190-196.
[8]Kim I,Lee B,Song D S,et al.Effects of ammonium carbonate pretreatment on the enzymatic digestibility and structural features of rice straw[J].Bioresource Technology2014,166:353-357.
[9]Domanski J,Borowski S,Marchut-Mikolajczyk O,et al Pretreatment of rye straw with aqueous ammonia for conversion to fermentable sugars as a potential substrates in biotechnological processes[J].Biomass&Bioenergy,2016,91:91-97.
[10]Antonopoulou G,Jonuzaj S,Gavala H N,et al.The effect of aqueous ammonia soaking pretreatment on methane generation uing different lignocellulosic feedstocks[J].Waste&Biomass Valorization,2015,6(3):281-291.
[11]Ngamprasertsith S,Sunphorka S,Kuchonthara P,et al.Pretreatment of rice straw by hot-compressed water for enzymatic saccharification[J].Korean Journal of Chemical Engineering,2015,32(10):2007-2013.
[12]刘翀,张瑞婷,刘本国,等.蒸汽爆破处理对麦麸的酚酸组成及其抗氧化活性的影响[J].农业工程学报,201632(6):308-314.Liu Chong,Zhang Ruiting,Liu Benguo,et al.Effect of steam explosion treatment on phenolic acid compositionof wheat bran and its antioxidant capacity[J].Transactions of the Chinese Society of Agricultural Engineering(Transactions of the CSAE),2016,32(6):308-314.(in Chinese with English abstract)
[13]马欢,刘伟伟,刘萍,等.微波预处理对水稻秸秆糖化率与成分和结构的影响[J].农业机械学报,2014,45(10):180-186.MaHuan,LiuWeiwei,Liu Ping,et al.Effects of microwave pretreatment on enzymatic saccharification and lignocellulosic structure of rice straw[J].Transactions of the Chinese Society of Agricultural Machinery,2014,45(10):180-186.(in Chinese with English abstract)
[14]Zhong C,Lau M W,Balan V,et al.Optimization of enzymatic hydrolysis and ethanol fermentation from AFEX-treated rice straw[J].Applied Microbiology and Biotechnology,2009,84(4):667-676.
[15]Hou X D,Smith T J,Li N,et al.Novel renewable ionic liquids as highly effective solvents for pretreatment of rice straw biomass by selective removal of lignin[J].Biotechnology and Bioengineering,2012,109(10):2484-2493.
[16]Yang L F,Cao J,Mao J Y,et al.Sodium carbonate-sodium sulfite pretreatment for improving the enzymatic hydrolysis of rice straw[J].Industrial Crops and Products,2013,43:711-717.
[17]Garlock R J,Balan V,Dale B E,et al.Comparative material balances around pretreatment technologies for the conversion of switchgrass to soluble sugars[J].Bioresource Technology2011,102(24):11063-11071.
[18]Nguyen T A,Kim K R,Han S J,et al.Pretreatment of rice straw with ammonia and ionic liquid for lignocellulose conversion to fermentable sugars[J].Bioresource Technology2010,101(19):7432-7438.
[19]Kumar R,Mago G,Balan V,et al.Physical and chemical characterizations of corn stover and poplar solids resulting from leading pretreatment technologies[J].Bioresource Technology,2009,100(17):3948-3962.
[20]Nissila M E,Lay C,Puhakka J A,et al.Dark fermentative hydrogen production from lignocellulosic hydrolyzates-Areview[J].Biomass&Bioenergy,2014,67:145-159.
[21]Zhao C,Ma Z Q,Shao Q J,et al.Enzymatic hydrolysis and physiochemical characterization of corn leaf after H-AFEXpretreatment[J].Energy&Fuels,2016,30(2):1154-1161.
[22]Umagiliyage A L,Choudhary R,Liang Y,et al.Laboratory scale optimization of alkali pretreatment for improving enzymatic hydrolysis of sweet sorghum bagasse[J].Industrial Crops and Products,2015,74:977-986.
[23]Shao Q,Chundawat S P,Krishnan C,et al.Enzymatic digestibility and ethanol fermentability of AFEX-treated starch-rich lignocellulosics such as corn silage and whole corn plant[J].Biotechnology for Biofuels,2010,3(1):12.
[24]Li Q M,Li X J,Jiang Y L,et al.Analysis of degradation products and structural characterization of giant reed and Chinese silvergrass pretreated by 60Co-γirradiation[J].Industrial Crops and Products,2016,83:307-315.
[25]Garlock R J,Balan V,Dale B E.Optimization of AFEX?pretreatment conditions and enzyme mixtures to maximize sugar release from upland and lowland switchgrass[J].Bioresource Technology,2012,104:757-768.
[26]Rabelo S C,Andrade R R,Maciel Filho R,et al.Alkaline hydrogen peroxide pretreatment,enzymatic hydrolysis and fermentation of sugarcane bagasse to ethanol[J].Fuel,2014,136:349-357.
[27]Gao M T,Yano S,Inoue H,et al.Combination of wet disk milling and hydrogen peroxide treatments for enhancing saccharification of sugarcane bagasse[J].Biochemical Engineering Journal,2012,68:152-158.
[28]赵相君.农作物秸秆液氨-过氧化氢预处理参数优化及酶解效果研究[D].杭州:浙江农林大学,2013.
[29]Singh R,Tiwari S,Srivastava M,et al.Experimental study on the performance of microwave assisted Hydrogen peroxide(H2O2)pretreatment of rice straw[J].Agricultural Engineering International:The CIGR Journal,2014,16(1):173-181.
[30]Zhao C,Cao Y,Ma Z Q,et al.Optimization of liquid ammonia pretreatment conditions for maximizing sugar release from giant reed(Arundo donax L.)[J].Biomass&Bioenergy,2017,98(2):61-69.