玉米芯氨水预处理及酶解工艺研究

为有效提高木质纤维素酶解转化率,文中以玉米芯为研究对象,在常压中温下采用氨水浸泡工艺处理原料,考察了预处理条件对木质素脱除率和纤维素、半纤维素酶解转化率的影响规律。确定了最适预处理条件:氨水质量分数为15%、固液质量体积比为1∶6 g/mL、反应温度为60℃和预处理时间为12 h。该条件下纤维素、半纤维素回收率和木质素脱除率分别为94.5%,86.7%和48.1%;在每g葡聚糖加入30 FPU纤维素酶和60 CBUβ-葡萄糖苷酶条件下,酶解24 h后纤维素和半纤维素酶解转化率分别可达83.0%和81.6%。     

低共熔溶剂协同酸性二氧六环预处理杨木及其酶水解特性的探究

以杨木为原料,采用低共熔溶剂(DES)协同酸性二氧六环进行预处理,研究盐酸浓度、预处理时间和预处理温度对杨木酶水解特性的影响。结果表明,当盐酸质量分数为1%,反应温度为110℃,时间为70 min时,酶水解得率为69.75%,纤维素保留率为73.66%、半纤维素和木质素脱除率分别为72.61%和48.71%。协同预处理在保留纤维素的同时,可显著提高杨木中半纤维素和木质素的脱除率。同时,预处理能够大大提高杨木的结晶度,破坏杨木的致密结构,影响其热稳定性,进而有效提高纤维素酶水解得率。     

氧气辅助湿热预处理对玉米秸秆酒精发酵的影响

为了解氧气（O₂）在玉米秸秆湿热预处理中的作用,优化玉米秸秆酒精生产工艺,本文采用三种不同湿热预处理条件处理玉米秸秆,即条件1（195℃,15min）、条件2（195℃,15min,12bar O₂）和条件3（195℃,15min,12bar O₂,2g/L Na₂CO₃）,并利用酿酒酵母对预处理后的玉米秸秆同步糖化发酵酒精工艺（SSF）进行了研究。实验结果表明：经过预处理,玉米秸秆分为固体滤饼与水解液两部分,其中绝大部分纤维素以固体形式保留在滤饼中,而半纤维素和木质素由于不稳定则发生了部分水解或降解。三种预处理条件下纤维素总体收率分别为91.2%、94.6%和95.9%,半纤维素总体收率分别为74.5%、50.3%和68.2%,固体滤饼中木质素质量分数分别为25.2%、17.5%和13.7%,纤维素酶解葡萄糖率分别为64.8%、65.8%和67.6%。表明氧气对纤维素收率影响不大,能够促进半纤维素的溶出。氧气主要与木质素发生反应,尤其与碱性物质碳酸钠（Na₂CO₃）结合,能够促进木质素降解,从而获得了较高的纤维素收率和纤维素酶解葡萄糖率。因此在底物质量分数8%,经过酿酒酵母142h发酵,经条件3处理的玉米秸秆获得的酒精浓度最高,最终酒精浓度达到25.0g/L,并且整个发酵过程没有明显的抑制作用产生。     

醇酸体系分离木质素对酶解性能的影响

为提高生物质纤维素酶解性能,采用乙二醇耦合对甲基苯磺酸(EG-PTSA)法对玉米秸秆进行预处理,考察了温度、对甲基苯磺酸(PTSA)质量分数、反应时间对酶解性能的影响,并通过扫描电镜(SEM)、X射线衍射(XRD)和傅里叶变换红外光谱仪(FTIR)对预处理前后的样品进行表征分析。结果表明:在对甲基苯磺酸质量分数2.0%、100℃、60 min下,木质素脱除率为83.2%,纤维素保留率为83.5%;同时,酶解纤维素的葡聚糖产率从23.8%提高至71.4%(5 FPU/g),比原始玉米秸秆的酶解效率(23.8%)高出近3倍。SEM、XRD和FTIR分析表明,玉米秸秆经EG-PTSA预处理后,木质素、半纤维素大量脱除打破了秸秆纤维素致密结构,增加了纤维素酶的可及性,提高了酶解性能,是一种简单、高效且有前景的预处理方法。     

NaOH/AQ预处理对玉米秸秆脱木质素及酶解性能的影响

对玉米秸秆进行氢氧化钠/蒽醌（NaOH/AQ）去木质化预处理,考察了预处理温度、时间和NaOH用量对玉米秸秆脱木质素程度的影响,并探讨了脱木质素程度对提高预处理后物料酶解性能的影响。L₉（3⁴）正交试验得出较适宜预处理工艺条件为：温度160℃,时间60 min,NaOH用量（以绝干原料质量计）2.8%;其他条件为AQ用量0.05%,固液比1：5（g：mL）,此时木质素脱除率为75%,酶解后聚糖转化率达到73.79%。随着物料脱木质素程度的提高,其酶解效率相应增加;当木质素脱除率达到一定程度后,预处理后的聚糖转化率达到最大值,继续提高木质素脱除率,聚糖转化率反而降低。响应面优化的酶水解工艺条件为纤维素酶用量30 FPU/g,β-葡萄糖苷酶10 IU/g,反应时间72 h,温度50℃,底物质量分数2.5%,此时还原糖得率为85.62%。对酶解液进行HPLC分析,酶解液中的葡萄糖质量浓度为14.83 g/L,木糖质量浓度为4.83 g/L。XRD分析显示,预处理前后纤维素的晶型没有变化,而结晶度由31.40%提高至46.91%,表明物料中木质素和半纤维素发生了不同程度的溶出。     

碱性过氧化氢预处理小麦秸秆强化酶解产糖的研究

采用碱性过氧化氢对小麦秸秆进行预处理以提高其酶解效率。分别研究了过氧化氢浓度、预处理温度、预处理时间对麦秆化学成分及酶解产糖效率的影响,确定出最佳预处理条件为:Na OH质量分数为2.0%碱性环境,H_2O_2质量分数为2.0%,30℃处理24小时。经过处理的样品中纤维素含量为50.43%,纤维素保留率为89.52%,木质素脱除率为48.66%,半纤维素脱除率为41.81%,经预处理的样品酶解率达94.18%。此外,对预处理后的样品进行了SEM和FT-IR表征,分析预处理对原料形貌及官能团变化的影响。     

碱预处理糠醛渣性质及其纤维素酶解研究

以糠醛渣为原料进行碱法预处理,对比了处理前后的样品成分、结晶度、表面特性、红外谱图的变化以及对纤维素酶解的影响。研究结果表明:经NaOH处理样品,木质素脱除量随着温度升高而增加,120 ℃ 处理后的样品木质素脱除了 10.22 %,而碱性过氧化氢处理样品木质素脱除率达到 12.6 %。NaOH预处理后的样品酶解糖化率随处理温度的升高而降低。每克纤维素加入纤维素酶 12 FPU、纤维二糖酶 15 IU,120 ℃ 经NaOH预处理样品,酶解 72 h 后糖化率为38.6%,比原料糠醛渣低21.0个百分点,而经 60 ℃,6 h 碱性过氧化氢处理后的样品,酶解 72 h 糖化率可达到 86.6 %,比原料糠醛渣高27.0个百分点。NaOH预处理后样品红外谱图检测,证明生成了新的醚键。碱法预处理后的样品结晶度要比未处理的样品的稍高,且表面更加光滑。     

碱-氧-蒽醌蒸煮法制取麦草浆纤维素的酶解

用碱-氧-蒽醌蒸煮麦草所得纤维素为原料,研究了纤维素酶解的影响因素.结果表明:预处理后的麦草纤维素,其木质素含量较低,而酶解率和木质素脱除率均较高,在45～50℃、pH为4.4、底物与酶量之比为1:0.02、反应时间为30h、转速为100r/min时,可获得较理想的酶解率和木质素脱除率,二者分别可达74.5%和19.2%.     

水热预处理竹子促进酶解的效果及其影响因素

采用间歇式水热预处理装置,研究了水热预处理用于竹子的酶解规律,探讨了不同温度、处理时间、纤维素酶添加量及原料种类对促进竹子酶解的效果及其影响。结果表明水热预处理能显著提升竹子的酶解率,在优化条件190℃、10 min水热预处理,添加15 FPU·(g葡聚糖)^-1纤维素酶,72 h葡聚糖与木聚糖酶解率分别为74.3%、54.0%,提高到原来的3.5倍和4.7倍。过高的预处理温度与过长的预处理时间都将导致木糖大量降解和部分葡萄糖降解,使单糖总量下降。纤维素酶的添加量从15 FPU·(g 葡聚糖)^-1提高到60 FPU·(g 葡聚糖)^-1,可使未作预处理和水热预处理竹子的总糖回收率分别提高21.5%和9.9%,其促进酶解的作用远低于预处理的效果,通过预处理增大酶的可及性是提高酶解率的关键。水热预处理对于生物质原料具有选择性,不同的竹子原料具有显著不同的效果。     

碱性双氧水法预处理木质纤维素

在采用木质纤维素制备燃料乙醇工艺中,纤维素酶对纤维素物质的可及性对纤维素的酶解过程非常重要,木质纤维素物质的预处理过程就是通过溶解木质素、半纤维素以及破坏纤维素的结晶结构,以提高纤维素酶的可及性.采用碱性双氧水法处理木质纤维素,应用部分重复因子设计的实验方法考察了反应时间(tR)、反应温度(Te)、双氧水用量(ch)、液固比(Vr)和 NaOH浓度(cb)5个因素对预处理效果的影响,确定tR＝18 h、Te＝70℃、ch＝1%、Vr＝8 g·L-1、cb＝10 g·L-1为较优化的条件.     

Pretreatment of Corn Stover Using Supercritical CO2 with Water-Ethanol as Co-solvent

Supercritical carbon dioxide, with water-ethanol as co-solvent, was applied to pretreat corn stover to enhance its enzymatic hydrolysis. The efficiency of pretreatment was evaluated by the final reducing sugar yield obtained from the enzymatic hydrolysis of cellulose. Under the operation conditions of pretreatment pressure 15 MPa, temperature 180 ℃ and time 1 h, the optimal sugar yield of 77.8℅ was obtained. Scanning electron microscopy (SEM) and chemical composition analysis were applied to the pretreated corn stover. The results showed that the surface morphology and microscopic structure of pretreated corn stover were greatly changed. After the pretreatment, the contents of hemicellulose and lignin were reduced obviously. Thus more cellulose was exposed, increasing the sugar yield.     

Pretreatment Strategies to Enhance Enzymatic Hydrolysis and Cellulosic Ethanol Production for Biorefinery of Corn Stover

There is a rising interest in bioethanol production from lignocellulose such as corn stover to decrease the need for fossil fuels, but most research mainly focuses on how to improve ethanol yield and pays less attention to the biorefinery of corn stover. To realize the utilization of different components of corn stover in this study, different pretreatment strategies were used to fractionate corn stover while enhancing enzymatic digestibility and cellulosic ethanol production. It was found that the pretreatment process combining dilute acid (DA) and alkaline sodium sulfite (ASS) could effectively fractionate the three main components of corn stover, i.e., cellulose, hemicellulose, and lignin, that xylose recovery reached 93.0%, and that removal rate of lignin was 85.0%. After the joint pretreatment of DA and ASS, the conversion of cellulose at 72 h of enzymatic hydrolysis reached 85.4%, and ethanol concentration reached 48.5 g/L through fed-batch semi-simultaneous saccharification and fermentation (S-SSF) process when the final concentration of substrate was 18% (w/v). Pretreatment with ammonium sulfite resulted in 83.8% of lignin removal, and the conversion of cellulose and ethanol concentration reached 86.6% and 50 g/L after enzymatic hydrolysis of 72 h and fed-batch S-SSF, respectively. The results provided a reference for effectively separating hemicellulose and lignin from corn stover and producing cellulosic ethanol for the biorefinery of corn stover.     

电解水预处理对玉米秸秆和柳枝稷酶解产糖的研究

预处理是利用生物质原料制备燃料乙醇的工艺过程中至关重要的一步。以电解水为介质对玉米秸秆和柳枝稷进行预处理,考察了不同预处理条件对这两种生物质酶催化水解性能的影响。玉米秸秆预处理试验条件为:165、180和195℃;10、20和30 min。柳枝稷预处理试验条件为:170、185和200℃;5、15和25 min。结果表明,电解水预处理法针对不同的生物质有较好的处理效果,在玉米秸秆和柳枝稷的试验中,分别获得了83%和67%的纤维素转化率。同时,电解水预处理过程中,木糖只有在较高温度(195℃和200℃)时,才发生明显的降解。HPLC检测表明预处理过程中生成的发酵抑制物较少。     

不同预处理方式对玉米叶和玉米秆酶解率的影响

1 INTRODUCTION Enzymatic hydrolysis of the cellulose to glucose from inexpensive and abundant sources, followed by ethanol fermentation to produce alternative liquid transportation fuels is very attractive[1―4]. However, lignocellulosic biomass must first be pretreated to open up its structure, so that the high yields vital to economic success can be realized. Pretreatment is currently one of the most expensive steps in such bio- conversion routes, which account for one-third of the total…     

微波烘焙预处理降解玉米秸秆

用微波可高效对生物质烘焙预处理,考察了不同微波烘焙过程对玉米秸秆主要组分的降解作用及酸、碱、甘油催化剂对纤维素转化效率的影响,并对预处理的玉米秸秆进行酶解实验。结果表明,单纯的微波预处理对玉米秸秆中主要组分纤维素、半纤维素和木质素均有强烈的转化作用。无催化剂微波烘焙后,样品中纤维素含量降低了30%。在微波烘焙中添加酸、碱、甘油催化剂,可选择性降解玉米秸秆中的半纤维素或木质素,有效提高预处理后玉米秸秆中的纤维素含量,添加NaOH后纤维素含量增加最明显,由33%增至42%,纤维素最高转化率达65%。     

弱碱性过氧化预处理对稻草秸秆酶解糖化的影响

为了提高稻草秸秆的酶解糖化率,对稻草秸秆弱碱性过氧化预处理条件进行了优化。结果表明:弱碱性过氧化预处理降低了稻草秸秆中木质素的含量,提高了纤维素的含量。最优预处理条件为温度40 ℃,时间24 h,H₂O₂质量分数为2.0 %,在此条件下稻草秸秆的酶解糖化率达到了83.23 %,而在相同酶解条件下,预处理温度30 ℃、时间24 h、 2.0 % NaOH处理后稻草秸秆的酶解糖化率为70.38 %。弱碱性过氧化预处理稻草秸秆的糖化率明显高于碱性预处理稻草秸秆的糖化率。同时试验结果表明,木质素的除去率与H₂O₂质量分数有关。当H₂O₂质量分数大于2.0 %后,H₂O₂对木质素的除去选择性降低,木质素的除去率基本保持不变,却增加了半纤维素的损失。     

Enzymatic hydrolysis from carbohydrates of barley straw pretreated by ionic liquids

BACKGROUND: Lignocellulosic biomass offers many potential advantages in comparison with the traditionally used sugars or starchy biomass since it is very widely available and does not compete with food and feed production. The abundance and high carbohydrates content of barley straw make it a good candidate for bioethanol production in Europe. Since biomass must be pretreated before enzymatic hydrolysis to improve the digestibility of both the cellulose and the hemicellulose biomass, the use of ionic liquids (IL) has been proposed as an environment‐friendly pretreatment of biomass. RESULTS: Different pretreatment conditions were investigated to determine the effects of the experimental conditions (temperature and time) on the enzymatic digestibility of pretreated material. The pretreatment of barley straw with 1‐ethyl‐3‐methyl imidazolium acetate treatment resulted in up to a 9‐fold increase in the cellulose conversion and a 13‐fold increase in the xylan conversion when compared with the untreated barley straw. CONCLUSION: Ionic liquid pretreatment of barley straw at 110°C for 30 min, followed by enzymatic hydrolysis, leads to a sugar yield of 53.5 g per 100 g raw material. It is then ready available for conversion into ethanol and is equivalent to more than 86% from potential sugars. The increase in saccharification was possible due to rupture of the lignin–hemicellulose linkages by treatment with 1‐ethyl‐3‐methyl imidazolium acetate. © 2012 Society of Chemical Industry