蒸汽爆破预处理对橡子壳酶水解效果的影响

将橡子壳作为原料,考察蒸汽爆破预处理对其化学组成变化以及纤维素酶水解得率的影响,并采用电子扫描电镜、X-射线衍射分析、红外光谱分析对橡子壳纤维结构特征进行表征。结果表明:蒸汽爆破预处理后,纤维素含量达到43.0%,较处理前提高24.6%,半纤维素含量降低28.9%,同时也去除部分木质素;预处理后酶水解得率达到98.8%,较处理前提高130%;总体葡萄糖产率达到84.8%,较处理前提高了98%。经蒸汽爆破预处理后,橡子壳纤维比表面积增大、表面孔洞增加,纤维结构的结晶度下降,有利于纤维素酶水解作用的进行。     

蒸汽爆破预处理对玉米芯酶水解的影响

采用不同的蒸汽爆破条件对玉米芯进行预处理,研究蒸汽爆破对玉米芯理化性质和酶水解的影响。结果表明:蒸汽爆破条件为1.4 MPa,300 s时,玉米芯酶水解液中总糖浓度最高为58.17 g/L。蒸汽爆破预处理主要引起半纤维素大量降解,但过高的压力或过长的保压时间会使木糖进一步降解,从而使玉米芯水解糖得率降低。X-衍射结果表明:经1.4 MPa,300 s蒸汽爆破的玉米芯结晶度由对照的24.49%提高到43.09%。由扫描电镜可知,蒸汽爆破可提高玉米芯的孔隙度和表面积,从而提高酶水解效率。     

稀碱法预处理对橡子壳酶水解效果的影响

首次将橡子壳作为原料,考察了碱法预处理对其化学组成变化以及纤维素酶水解得率的影响,并采用电子扫描电镜、X-射线衍射分析、红外光谱分析对橡子壳纤维结构特征进行了表征。结果表明:利用2%氢氧化钠溶液室温处理48 h时,半纤维素和木素去除率分别为29.9%和15.6%,纤维素含量达到47.0%,较处理前提高了36.2%;酶水解得率从42.8%增加至76.0%,提高了77.6%;总体葡萄糖产率达到73.5%,提高了71.7%。经过在121℃(0.15 MPa)下处理1 h,纤维素损失率较高,导致总体葡萄糖产率增幅不大。经过碱处理后,橡子壳纤维比表面积增大、表面孔洞增加,纤维结构的结晶度下降,有利于纤维素酶水解作用的进行。该试验为橡子壳酶水解工艺的进一步研究提供了依据。     

浓H_3PO_4联合H_2O_2预处理能源植物地肤的性能研究

采用H_3PO_4联合H_2O_2(简称PHP)预处理地肤,基于木质素、半纤维素去除率、纤维素回收率、酶水解率等,研究温度、时间、H_3PO_4与H_2O_2浓度配比对预处理效果的影响。结果表明:提升预处理温度、时间和H_3PO_4浓度配比对半纤维素和木质素去除率有明显的促进作用,半纤维素和木质素去除率最大可达100.0%和90.7%,但也会加剧纤维素的损失。过高的H_3PO_4浓度配比(≥70%)不利于半纤维素和木质素去除。除10℃外,其他条件下,酶水解率差异不显著(90%),但过高强度会导致一定程度的水解速率下降。     

木屑纤维素酶水解条件的试验研究

采用正交试验法研究了稀盐酸预处理木屑的最优条件:反应温度为105℃,反应时间为3 h,用质量分数为2%的HCl预处理后,半纤维素质量分数降低了78.4%,木质素降低了29.3%.用纤维素酶水解预处理过的木屑,考察了pH值、温度、时间对酶水解率的影响,结果表明:酶解温度为50℃,pH值为4.8,纤维素酶液用量为2 ml/g,水解时间为48 h时,酶水解率达到76%,纤维素质量分数降低了65.4%.     

水热和碱醇联合预处理麦草结构解析及酶解性能研究

采用水热(高温液态水)和碱醇联合预处理麦草秸秆,对处理后的物料进行组成分析和酶解研究,并对碱醇预处理液中的木质素进行回收提纯及结构表征。结果表明:水热预处理对半纤维素和酸溶木质素有较好的溶出作用,溶出率随水热温度的升高而增加。190℃为较优的水热处理温度,此温度下半纤维素和酸溶木质素的溶出率分别为76.56%和83.52%。碱醇预处理可将酸不溶的木质素从物料中有效分离,最终得到富含纤维素的物料(纤维素含量为89.71%)。X射线衍射(XRD)检测结果表明,由于半纤维素和木质素的溶出,物料的结晶度指数有所增大,从原料的28.80%增至预处理后的32.29%～33.59%。水热和碱醇联合预处理物料经30 FPU/g(以纤维素质量计)纤维素酶和30 IU/g的β-葡萄糖苷酶酶解72 h,物料的纤维素酶解率明显提高,达到94.97%,是麦草原料直接酶解的6.1倍。采用傅里叶红外光谱(FT-IR)对回收木素进行结构表征,结果表明与原料磨木木素相比,回收木质素中除部分C■O和C—O—C发生断裂外,其他基团得到较好的保留,回收木质素作为预处理副产物具有较大的应用价值。     

碱和双氧水预处理玉米秸秆的试验研究

研究了在5%NaOH中加入不同质量分数的双氧水时,对玉米秸秆的预处理效果;在预处理后的玉米秸秆中加入纤维素酶,考察此时酶解还原糖得率随预处理程度的变化;对浸泡时间、双氧水浓度、固液比3个因素进行单因素试验。试验结果表明,质量分数为2.5%的浓度下,糖得率最大;在2.5%H2O2浸泡24 h,固液比对酶解糖化几乎没有影响;当浸泡时间为24,72,96 h时,糖得率相差甚微。设计正交试验对预处理的条件进行优化,分析预处理玉米秸秆的各因素,以木质素去除率为基准参数,得到水解木质纤维素的适宜预处理条件:5%NaOH下加入质量分数为2.5%的双氧水,浸泡时间为72 h,固液比为1∶20。预处理后木质素的去除率为61.52%;加入纤维素酶酶解,还原糖得率为39.30%。     

竹材碱性过氧化氢预处理及其酶水解性能研究

采用碱性过氧化氢（AHP）体系对慈竹进行预处理,研究过氧化氢（H₂O₂）用量对竹材化学组分及酶水解得率的影响。利用X射线衍射（XRD）和傅里叶变换红外光谱仪（FTIR）分析预处理前后物料的物理和化学结构变化,采用二维核磁共振技术研究预处理物料中剩余木质素的化学结构。结果表明：AHP预处理过程中,随着H₂O₂用量（质量分数）的增加,竹材的葡聚糖含量（相对质量百分比）先增加后减少,木聚糖含量基本不变,而木质素含量整体呈减少趋势。AHP预处理能显著提升竹材的酶解效率,在纤维素酶用量为15 FPU/g葡聚糖,H₂O₂用量为7.0%时,预处理竹材的酶水解性能最高,葡聚糖和木聚糖酶水解得率分别为93.9%和100%。研究发现,慈竹木质素脱除率在H₂O₂用量达到2.0%后趋于稳定,为68.8%,继续增加H₂O₂用量,木质素脱除率无明显提升,对预处理竹材中剩余木质素进行2D-HSQC核磁分析,这部分难以脱除的木质素的化学结构为：64%的S单元、33.7%的G单元和61.6%的β——O——4键,其中S/G值为1.90。     

玉米秸秆预处理对厌氧发酵制氢影响的研究

为提高玉米秸秆的产氢能力,实验研究了蒸汽爆破预处理、硫酸预处理、氢氧化钠预处理、盐酸预处理和酸化(碱化)气爆预处理5种预处理方法对玉米秸秆发酵产氢能力的影响。结果表明,预处理可以将秸秆中相当一部分纤维素和半纤维素水解生成还原糖,其中质量分数为0.8%的H2SO4酸化汽爆预处理对秸秆的水解效果最好。在固-液比1∶10、H2SO4质量分数0.8%、保持微沸状态30min的处理条件下,秸秆的糖含量达到最大值24.57%,最大氢气产量为141mL/g。     

蒸汽爆破预处理玉米芯及其酶解工艺研究

以蒸汽爆破预处理后的玉米芯为原料,进行了玉米芯酶解工艺条件的研究。粉碎后的玉米芯在压力2.8 MPa、保压时间240 s条件下蒸汽爆破预处理,在初始固形物含量为14%(w/v),pH 5.0的条件下,分别添加纤维素酶15 FPA/g(底物)、木聚糖酶225 IU/g(底物),同时添加环境因子MgSO40.005 g/g(底物)、Tween-800.001 g/g(底物),糖化48 h后,还原糖浓度达到71.81 g/L,糖化率达到80.85%。试验结果表明,蒸汽爆破预处理及添加适量环境因子对玉米芯的糖化效果影响显著。     

Pretreatment and fractionation of barley straw using steam explosion at low severity factor

Agricultural residues represent an abundant, readily available, and inexpensive source of renewable lignocellulosic biomass. However, biomass has complex structural formation that binds cellulose and hemicellulose. This necessitates the initial breakdown of the lignocellulosic matrix. Steam explosion pretreatment was performed on barley straw grind to assist in the deconstruction and disaggregation of the matrix, so as to have access to the cellulose and hemicellulose. The following process and material variables were used: temperature (140–180 °C), corresponding saturated pressure (500–1100 kPa), retention time (5–10 min), and mass fraction of water 8–50%. The effect of the pretreatment was assessed through chemical composition analysis. The severity factor R_o, which combines the temperature and time of the hydrolytic process into a single reaction ordinate was determined. To further provide detailed chemical composition of the steam exploded and non-treated biomass, ultimate analysis was performed to quantify the elemental components. Data show that steam explosion resulted in the breakdown of biomass matrix with increase in acid soluble lignin. However, there was a considerable thermal degradation of cellulose and hemicellulose with increase in acid insoluble lignin content. The high degradation of the hemicellulose can be accounted for by its amorphous nature which is easily disrupted by external influences unlike the well-arranged crystalline cellulose. The carbon content of the solid steam exploded product increased at higher temperature and longer residence time, while the hydrogen and oxygen content decreased, and the higher heating value (HHV) increased.     

The effect of temperature and hemicellulose-lignin,cellulose-lignin,and cellulose-hemicellulose on char yield from the slow pyrolysis of rice husk

In this work, the effect of temperature on the char yield of untreated rice husk, cellulose removed (hemicellulose + lignin), hemicellulose removed (cellulose + lignin), and lignin removed (cellulose + hemicellulose) is investigated. The work compares the performance of acid and alkaline hydrolysis in the context of lignin removal as well. The effect of hemicellulose-lignin, cellulose-lignin, and cellulose-hemicellulose on char yield during slow pyrolysis of rice husk is also studied. The study reveals that only low temperatures favor char yield. Alkaline hydrolysis effects better lignin removal than acid hydrolysis. The effect of hemicellulose-lignin on char yield is more than cellulose-lignin and cellulose-lignin.     

四氢糠醇-稀酸体系预处理杂交狼尾草的试验研究

以杂交狼尾草为研究对象,采用四氢糠醇-硫酸体系在常压较低温度下进行预处理研究,优化该预处理体系得到最佳预处理条件为0.1 mol/L硫酸、反应温度120℃、反应时间2 h、固液比为1∶12,在此条件下残渣中纤维素、半纤维素的保留率分别为86.17%、9.01%,木质素脱除率为98.16%;对预处理残渣进行酶解,72 h时酶解率可达99.01%,比未处理原料的酶解率高2.6倍。通过使用扫描电镜、X射线衍射、红外光谱、热重分析等方法对预处理后残渣及原料的组成及结构进行分析测试,表明四氢糠醇-硫酸预处理能有效脱除木质素及半纤维素,破坏平整的原料表面结构,提高原料的酶解率。     

Evaluation of wet air oxidation as a pretreatment strategy for bioethanol production from rice husk and process optimization

The pretreatment of rice husk by the wet air oxidation (WAO) technique was investigated by means of a statistically designed set of experiments. Reaction temperature, air pressure, and reaction time were the process parameters considered. WAO pretreatment of rice husk increased the cellulose content of the solid fraction by virtue of lignin removal and hemicellulose solubilization. The cellulose recovery was around 92%, while lignin recovery was in the tune of 8–20%, indicating oxidation of a bulk quantity of lignin. The liquid fraction was found to be rich in hexose and pentose sugars, which could be directly utilized as substrate for ethanol fermentation. The WAO process was optimized by multi-objective numerical optimization with the help of MINITAB 14 suite of statistical software, and an optimum WAO condition of 185 °C, 0.5 MPa, and 15 min was predicted and experimentally validated to give 67% (w/w) cellulose content in the solid fraction, along with 89% lignin removal, and 70% hemicellulose solubilization; 13.1 gl^?1 glucose and 3.4 gl^?1 xylose were detected in the liquid fraction. The high cellulose content and negligible residual lignin in the solid fraction would greatly facilitate subsequent enzymatic hydrolysis, and result in improved ethanol yields from rice husk.     

改进的柳枝稷预处理方法及乙醇发酵研究

为了提高柳枝稷中纤维素和半纤维素糖的转化率,降低水解液中抑制剂的浓度,首先,用稀酸在温和条件下对柳枝稷进行水解,然后用碱对酸水解后的固体物进行预处理,接着用纤维素酶酶解并分别对稀酸水解液和酶解液进行乙醇发酵.结果表明:纤维素转化率达到94.26%,半纤维素转化率为60.93%,稀酸水解液乙醇发酵的乙醇产率为0.441g乙醇/g糖,达到最高理论值的86.47%.酶解液乙醇发酵的乙醇产率为0.486g乙醇/g葡萄糖,达到最高理论值的95.29%.     

Bioethanol production from pretreated Miscanthus floridulus biomass by simultaneous saccharification and fermentation

The production of ethanol from the fast-growing perennial C4 grass Miscanthus floridulus by simultaneous saccharification and fermentation (SSF) was investigated. M. floridulus biomass was composed of 36.3% glucan, 22.8% hemicellulose, and 21.3% lignin (based on dried mass). Prior to SSF, harvested stems of M. floridulus were pretreated separately by alkali treatment at room temperature, alkali treatment at 90 °C, steam explosion, and acid-catalyzed steam explosion. The delignification rates were determined to be 73.7%, 61.5%, 42.7%, and 63.5%, respectively, by these four methods, and the hemicellulose removal rates were 51.5%, 85.1%, 70.5%, and 97.3%, respectively. SSF of residual solids after various pretreatments was performed with dried yeast (Saccharomyces cerevisiae) and cellulases (Accellerase 1000) by using 10% water-insoluble solids (WIS) of the pretreated M. floridulus as the substrate. The ethanol yields from 72-h SSF of M. floridulus biomass after these pretreatments were 48.9 ± 3.5, 78.4 ± 1.0, 46.4 ± 0.1, and 69.0 ± 0.1% (w/w), respectively, while the ethanol concentrations after 72-h SSF were determined to be 15.4 ± 1.1, 27.5 ± 0.3, 13.9 ± 0.1, and 30.8 ± 0.1 g/L, respectively. Overall, the highest amount of ethanol (0.124 g/g-dried raw material) was generated from dried raw material of M. floridulus after alkaline pretreatment at 90 °C. The acid-catalyzed steam explosion pretreatment also resulted in a high ethanol yield (0.122 g/g-dried raw material). Pretreatment resulting in high lignin and hemicellulose removal rates could make biomass more accessible to enzyme hydrolysis and lead to higher ethanol production.     

New process of maize stalk amination treatment by steam explosion

Amination treatment of straw proceeds slowly at the low environmental temperatures. Although the aqueous ammonia has a relatively good effect, it has high volatility and an irritant odor. Steam explosion has the advantage of short reaction time, but it cannot improve the nitrogen content of the straw for animal feed. A new process combined with the two methods for maize stalk pretreatment was studied to improve its nutritive value. The results showed that nitrogen sources coupled with steam explosion modified the treated materials. Except for urea, other nitrogen sources promoted the degradation of hemicellulose and the increase of the soluble sugars content. Decrease of hemicellulose treated with 5% (NH₄)₂SO₃ was highest (58.0%), but no significant changes were detected in cellulose and lignin content using chemical methods after nitrogen source addition. Compared with steam explosion pretreatment, amination by steam explosion increased the nitrogen content of maize stalk. The highest total nitrogen content (2.30%) was obtained by adding urea. The treatment of 5% (NH₄)₂SO₃ led to the highest retention of added nitrogen (84.0%) and 15% NH₄OH led to the lowest percentage of retention (18.1%). Amination by steam explosion effectively increased the potential digestibility of DM, and the maximum digestibility value (71.2%) was obtained when 5% (NH₄)₂SO₃ was added. Amination by steam explosion shortened the amination time and was a rapid and effective method of improving the nutritive value of straw.     

Combined ethanol and methane production from switchgrass (Panicum virgatum L.) impregnated with lime prior to steam explosion

Pretreatments are crucial to achieve efficient conversion of lignocellulosic biomass to soluble sugars. In this light, switchgrass was subjected to 13 pretreatments including steam explosion alone (195 °C for 5, 10 and 15 min) and after impregnation with the following catalysts: Ca(OH)₂ at low (0.4%) and high (0.7%) concentration; Ca(OH)₂ at high concentration and higher temperature (205 °C for 5, 10 and 15 min); H₂SO₄ (0.2% at 195 °C for 10 min) as reference acid catalyst before steam explosion. Enzymatic hydrolysis was carried out to assess pretreatment efficiency in both solid and liquid fraction. Thereafter, in selected pretreatments the solid fraction was subjected to simultaneous saccharification and fermentation (SSF), while the liquid fraction underwent anaerobic digestion (AD). Lignin removal was lowest (12%) and highest (35%) with steam alone and 0.7% lime, respectively. In general, higher cellulose degradation and lower hemicellulose hydrolysis were observed in this study compared to others, depending on lower biomass hydration during steam explosion. Mild lime addition (0.4% at 195 °C) enhanced ethanol in SSF (+28% than steam alone), while H₂SO₄ boosted methane in AD (+110%). However, methane represented a lesser component in combined energy yield (ethanol, methane and energy content of residual solid). Mild lime addition was also shown less aggressive and secured more residual solid after SSF, resulting in higher energy yield per unit raw biomass. Decreased water consumption, avoidance of toxic compounds in downstream effluents, and post process recovery of Ca(OH)₂ as CaCO₃ represent further advantages of pretreatments involving mild lime addition before steam explosion.     

N2 explosive decompression pretreatment of biomass for lignocellulosic ethanol production

This paper presents a novel biomass pretreatment method that uses high pressured N₂ and temperature to break the hemicellulose and lignin seal around the cellulose macro fibrils in the cell walls of the lignocellulosic biomass in order to open up the biomass structure for more efficient enzymatic hydrolysis. In this method the biomass is exposed to a high pressure using N₂ gas, and temperature. Under pressure, cells of the lignocellulosic biomass are filled with a solution saturated with nitrogen. When the pressure is then suddenly released, the feedstock is exposed to an explosive decompression and the dissolved nitrogen is released from the solution. Sudden change in the volume breaks the cell walls and opens the biomass structure resulting in increased surface area of the substrate for enzymatic hydrolysis. No catalysts or chemicals were added in the process thereby, making it economically and environmentally attractive. In this research, a range of different pressures (1–60 bar) and temperatures (25–175 °C) were applied to barley straw to evaluate the efficiency of the pretreatment. The pretreatment was followed by enzymatic hydrolysis and fermentation. Resulting glucose and ethanol concentrations were measured and the yields were considered as an estimate for the most suitable set of pretreatment conditions. The results indicate that the highest glucose yield and hydrolysis efficiency were gained at 150 °C and 10–30 bars. The fermentation efficiency was lower at higher temperatures. Nonetheless, the highest ethanol yield was still gained at the same conditions.     

Two-step steam pretreatment of softwood by dilute H2SO4 impregnation for ethanol production

Fuel ethanol can be produced from softwood through hydrolysis in an enzymatic process. Prior to enzymatic hydrolysis of the softwood, pretreatment is necessary. In this study two-step steam pretreatment by dilute H₂SO₄ impregnation to improve the overall sugar and ethanol yield has been investigated. The first pretreatment step was performed under conditions of low severity (180°C, 10 min, 0.5% H₂SO₄) to optimise the amount of hydrolysed hemicellulose. In the second step the washed solid material from the first pretreatment step was impregnated again with H₂SO₄ and pretreated under conditions of higher severity to hydrolyse a portion of the cellulose, and to make the cellulose more accessible to enzymatic attack. A wide range of conditions was used to determine the most favourable combination. The temperatures investigated were between 180°C and 220°C, the residence times were 2, 5 and 10 min and the concentrations of H₂SO₄ were 1% and 2%.

The effects of pretreatment were assessed by both enzymatic hydrolysis of the solids and with simultaneous saccharification and fermentation (SSF) of the whole slurry, after the second pretreatment step. For each set of pretreatment conditions the liquid fraction was fermented to determine any inhibiting effects. The ethanol yield using the SSF configuration reached 65% of the theoretical value while the sugar yield using the SHF configuration reached 77%. Maximum yields were obtained when the second pretreatment step was performed at 200°C for 2 min with 2% H₂SO₄. This form of two-step steam pretreatment is a promising method of increasing the overall yield in the wood-to-ethanol process.