Effect of several factors on peracetic acid pretreatment of sugarcane bagasse for enzymatic hydrolysis

BACKGROUND: Lignocellulose should undergo pretreatment to enhance its enzymatic digestibility before being saccharified. Peracetic acid (PAA) is a strong oxidant that can remove lignin under mild conditions. The sulfuric acid in the PAA solution also can cause degradation of hemicelluloses. The objective of the present work is to investigate the effect of several factors on peracetic acid pretreatment of sugarcane bagasse. RESULTS: It was found that PAA charge, liquid/solid (l/s) ratio, temperature, time, interactions between PAA charge and l/s ratio, temperature and time, all had a very significant effect on the enzymatic conversion ratio of cellulose. The relative optimum condition was obtained as follows: PAA charge 50%, l/s ratio 6:1, temperature 80 °C and time 2 h. More than 80% of the cellulose in bagasse treated under the above conditions was converted to glucose by cellulase of 20 FPU g^?1 cellulose. Compared with H₂SO₄ and NaOH pretreatments under the same mild conditions, PAA pretreatment was the most effective for enhancement of enzymatic digestibility. CONCLUSION: PAA pretreatment could greatly enhance the enzymatic digestibility of sugarcane bagasse by removing hemicelluloses and lignin, but removal of lignin was more helpful. This study can serve as a step to further optimization of PAA pretreatment and understanding the mechanism of enhancement of enzymatic digestibility. Copyright © 2007 Society of Chemical Industry     

过氧甲酸预处理对甘蔗渣酶解和发酵的影响

以甘蔗渣(SCB)为原料, 经过氧甲酸(PAP)预处理后加入酶进行水解, 并以水解液发酵产乙醇, 考察预处理时过氧化氢(HPP)浓度变化对甘蔗渣酶解和乙醇得率的影响。实验结果表明: 在甘蔗渣PAP预处理过程中, HPP与甲酸(FAP)体积比为1∶1时, 预处理甘蔗渣(PAP-SCB-1)的木质素脱除率达84.30%;在纤维素酶用量为10 FPIU/g(以预处理后的甘蔗渣质量计)时, PAP-SCB-1水解72 h葡萄糖得率为98.71%, 较单独过氧化氢预处理甘蔗渣(HPP-SCB, 葡萄糖得率9.11%)和单独甲酸预处理甘蔗渣(FAP-SCB, 葡萄糖得率7.06%), 分别提高了9.84和12.98倍; PAP-SCB-1水解液经24 h发酵后, 乙醇得率为84.06%, 比HPP-SCB(76.20%)和FAP-SCB(75.15%)均有增加。对预处理前后物料的化学成分变化、比表面积和结晶度进行测定, 结果显示: 经PAP预处理后可以显著脱除甘蔗渣中的木质素, 木质素的量由未经预处理的21.27%降低到10%以下; 比表面积和结晶度都有提高, PAP-SCB-1的比表面积和结晶度分别为13.01 m²/g和54.18%, 是HPP-SCB的10.66和1.11倍, FAP-SCB的11.39和1.15倍。     

Systematic Isolation and Utilization of Lignocellulosic Components from Sugarcane Bagasse

Lignocellulosic constituents as renewable feedstock can be utilized for various applications. A systematic procedure for separation of cellulose and lignin followed by hydrolysis of hemicelluloses was proposed in this study. Sugarcane bagasse was first subjected to alkaline hydrolysis to remove lignin and hemicelluloses. Then cellulose was separated from the alkali pretreatment residue and further purified. Meanwhile, the obtained pre-hydrolysis liquor (PHL) was acidified to precipitate lignin, and the filtrate was hydrolyzed with 1-methylimidazolium hydrogen sulfate ([Hmim]HSO₄) to prepare furfural. Response surface methodology (RSM) was employed to determine optimal conditions for isolation of cellulose. The sequential treatments resulted in a total release of over 77.3% of the original cellulose and 84.5% of the original lignin. In particular, 7.5% yield of furfural was obtained. The structures of the isolated cellulose and lignin were elucidated with Fourier transform infrared spectroscopy (FT-IR).     

Evaluation of the effects of operational parameters in the pretreatment of sugarcane bagasse with diluted sulfuric acid using analysis of variance

The pretreatment of lignocellulosic residues has been extensively studied as a method to disrupt the cellulose–hemicelluloses–lignin complex in biomass to access the sugars in their respective components. In this work, we carried out a study using sulfuric acid pretreatment of sugarcane bagasse by varying the following operational parameters: solid loading (10–30% of bagasse relative to the volume of the sulfuric acid solution), sulfuric acid concentration (0.5–2.5% relative to the dry mass of bagasse), reaction time (5–25?min), and temperature (135–195°C). The obtained solids from each pretreatment condition were submitted to enzymatic hydrolysis under the same process conditions: 0.232?g of Celluclast 1.5?L and 0.052?g of Novozym 188 per g of pretreated sugarcane bagasse, 72?h of hydrolysis, and 200?rpm of agitation at 50°C. Using central composite rotational design configuration in the experiments and analysis of variance, the results indicate that the conditions that produced larger quantities of glucose by enzymatic hydrolysis (0.35?g glucose/g pulp) with minimum amounts of degradation products were as follows: 20% solids loading, 15?min of reaction time, 1.5% sulfuric acid, and a minimum temperature of reaction of 170°C.     

氢氧化钠预处理对甘蔗渣酶解和发酵性能的影响

采用氢氧化钠预处理甘蔗渣,通过单因素和正交试验考察了不同预处理条件对甘蔗渣酶解和发酵性能的影响,并进一步分析了比表面积和木质素含量对酶解性能的影响。结果表明：预处理温度、氢氧化钠质量分数及预处理时间对酶解和发酵效率影响较为显著,最佳的预处理条件为：温度85℃、时间11 h、NaOH质量分数4.5%,在此优化条件下预处理的甘蔗渣,含纤维素56.46%,与原料相比提高了46.16%;半纤维素20.30%、Klason木质素5.79%,与原料相比分别降低了15.77%和72.87%,酶解36 h的还原糖得率为0.69 g/g（以甘蔗渣质量计）。经过氢氧化钠预处理后的甘蔗渣比表面积显著增加（由原料的0.07 m²/g最大可增加到1.07 m²/g）,木质素显著降低,有利于提高酶解和发酵效率。当比表面积超过0.30 m²/g时,酶解初始速率和酶解效率达到平衡;当木质素低于11%时,酶解效率达到平衡。     

Treatment of Harakeke fiber for biocomposites

The use of fiber from Harakeke (or New Zealand Flax plant) for the reinforcement of composites should be explored since Harakeke has similar properties to Sisal fiber. To maximize the cellulose content in the fiber, Harakeke fibers were prepared by thermal, combinative alkaline‐thermal, and a novel combinative thermal‐enzymatic‐thermal treatments and characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, and wide‐angle X‐ray spectroscopy. The characterization method provided an efficient and systematic method to evaluate the removal of amorphous components such as lignin and hemicelluloses. In particular, a sequential thermal‐enzymatic‐thermal fiber treatment produced fine discontinuous whiskers that could be useful for short fiber composites, whereas a combinative thermal‐alkaline treatment resulted in thorough extraction of lignin and hemicelluloses. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

甘蔗渣在高温液态水中的超微结构与组分变化

木质纤维素类物质中天然纤维素与半纤维素、木质素等组分交联形成了坚固的细胞壁,对纤维素酶水解和微生物消化表现出一定的抗性,原料预处理可以克服细胞壁抗性,提高木质纤维多糖生化转化效率.从细胞壁超微结构层次入手,对甘蔗渣细胞壁在高温液态水预处理过程中的解构机理进行了深入研究.未处理甘蔗渣细胞壁分层现象明显,由外至内分别为胞间层(ML)、初生壁(P)及次生壁(S),高温液态水预处理后各层界线变得模糊.SEM-EDXA分析表明细胞壁各层木质素分布发生了迁移,水解液中的木聚糖和木质素衍生物在细胞壁表面凝集生成类木质素滴状沉淀物.拉曼光谱分析结果显示预处理后纤维素在细胞壁各层分布趋于均质化.     

水热预处理工艺参数对玉米秸秆组分与酶解效率的影响

采用间歇式水热预处理方法,考察了不同水热预处理温度和处理时间对玉米秸秆主要成分变化的影响以及水热预处理后的纤维素酶解效率。在180～220℃,10～25 min范围内,随温度升高和时间延长预处理后半纤维素移除率和纤维素损失率也随之增大,但木质素质量并未减少反而有所增加。在210℃,25 min时得到最大半纤维素移除率为86.0%。以半纤维素移除率、木质素移除率和纤维素损失率为因变量,处理温度和处理时间为自变量通过多元线性回归分析或二次方程(多元线性回归方程拟合度不佳时)拟合分别获得回归模型。模型显示处理温度和处理时间对三者均具有显著影响。分析敏感性显示处理温度对三种因变量的影响均大于处理时间。经210℃,20 min处理后,纤维素酶解率最高为76.2%,继续提高处理温度和延长处理时间半纤维素移除率提高,但纤维素酶解率下降。     

New lignocellulose pretreatments using cellulose solvents: a review

Non‐food lignocellulosic biomass is the most abundant renewable bioresource as a collectable, transportable, and storable chemical energy that is far from fully utilized. The goal of biomass pretreatment is to improve the enzymatic digestibility of pretreated lignocellulosic biomass. Many substrate factors, such as substrate accessibility, lignin content, particle size and so on, contribute to its recalcitrance. Cellulose accessibility to hydrolytic enzymes is believed to be the most important substrate characteristic limiting enzymatic hydrolysis. Cellulose solvents effectively break linkages among cellulose, hemicellulose and lignin, and also dissolve highly‐ordered hydrogen bonds in cellulose fibers accompanied with great increases in substrate accessibility. Here the history and recent advances in cellulose solvent‐based biomass pretreatment are reviewed and perspectives provided for addressing remaining challenges. The use of cellulose solvents, new and existing, provides opportunities for emerging biorefineries to produce a few precursors (e.g. monosaccharides, oligosaccharides, and lignin) for the production of low‐value biofuels and value‐added biochemicals. © 2012 Society of Chemical Industry     

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。     

Long‐term lime pretreatment of poplar wood

Long‐term lime pretreatment has proven to increase digestibility of many herbaceous lignocellulose sources; but until this work, its effects had not been evaluated on wood, whose lignin content is higher, and therefore, more recalcitrant to enzymatic hydrolysis. In this study, the mild conditions of long‐term lime pretreatment (1‐atm pressure, temperatures ranging from 25 to 75°C, and reaction times between 1 and 12 weeks, with and without air) were systematically applied to poplar wood available in two batches with different lignin contents. These batches were designated as low‐lignin biomass (LLB) with lignin content of 21.4% and high‐lignin biomass (HLB) with lignin content of 29.1%. Full factorial designs resulted in 79 samples of pretreated poplar that were analyzed for lignin and carbohydrates pretreatment yields, and enzymatic digestibility (15 FPU/g glucan in raw biomass cellulose loading). After aerated lime pretreatment at 65°C for 4 weeks, and subsequent enzymatic hydrolysis, an overall yield of 0.76 g glucan + xylan recovered per gram glucan + xylan in raw biomass was obtained. This is equivalent to an increased poplar wood digestibility of 7.5‐fold compared with untreated biomass. Different batches of the feedstock resulted in different lignin and carbohydrates pretreatment yields; however, overall yields of carbohydrates (combining pretreatment and enzymatic hydrolysis) were similar. © 2010 American Institute of Chemical Engineers AIChE J, 2011     

蔗渣纤维组分的常压一步分离

蔗渣纤维组分的分离是实现其综合利用的关键,对蔗渣纤维组分进行了常压一步分离研究。采用溶剂-酸-水体系分离工艺,响应面法优化最佳工艺条件。结果表明,溶剂浓度69.63%(体积分数)、酸浓度(体积分数)6.41%、反应时间4h,蔗渣半纤维素分离率为98.07%、木质素分离率为66.72%、纤维素得率为92.49%,验证试验半纤维素分离率99%、木质素分离率67.06%、纤维素得率92.08%,分离条件可靠、分离结果较理想。最佳分离工艺条件下木糖得率90.01%,木质素回收率62.15%、分离的生物质总的可利用率71.53%。     

木薯酒精渣的预处理及补料同步糖化发酵制取乙醇

木薯酒精渣的处置是制约木薯燃料乙醇大规模产业化的问题之一。本文立足于探索木薯酒精渣利用途径,分析了木薯酒精渣的主要成分,对比了氨水、氢氧化钠、氨水组合稀硫酸3种预处理方式对于木薯酒精渣纤维素和木素含量及纤维素酶水解效率的影响,分析了处理前后木薯酒精渣的表面结构及纤维素结晶度,并以氨水处理后的木薯酒精渣为底物,进行了同步糖化发酵。结果表明,3种预处理方法中组合预处理能更好地增加纤维素含量和提高纤维素酶水解效率,与未处理原料相比,组合预处理后纤维素含量增加了111.26%,木素下降了35.05%,酶水解72h纤维素转化率从42.10%增加到61.71%。氨水预处理后,原料的木素含量降低,处理后木薯酒精渣的表面变得更加粗糙,纤维素结晶度有所增加,以氨水处理后的木薯酒精渣为底物进行分批补料同步糖化发酵,当初始底物浓度为100.0g/L,分别在20h、40h、60h进行补料至最终底物浓度为400.0g/L时,发酵120h乙醇浓度达到51.0g/L。     

Comparison of atmospheric aqueous glycerol and steam explosion pretreatments of wheat straw for enhanced enzymatic hydrolysis

BACKGROUND: The oversupply of cheap glycerol by the oleochemicals industry together with problems occurring in low‐boiling‐point organosolv pretreatments, has generated an interest in the use of glycerol in the organosolv pretreatment of lignocellulosic biomass. Atmospheric aqueous glycerol autocatalytic organosolv pretreatment (AAGAOP) is a promising strategy that can effectively enhance enzymatic hydrolysis of lignocellulosic biomass. As a cost‐effective technique, steam explosion pretreatment (SEP) is being adopted in industrial applications. Accordingly, work has been carried out to investigate how AAGAOP enhanced enzymatic hydrolysis of lignocellulosic biomass compares with the SEP method. RESULTS: Under controlled laboratory conditions, based on ≥ 90% cellulose recovery, AAGAOP removed ≥ 60% hemicellulose and ≥ 60% lignin from wheat straw while SEP led to ～80% hemicellulose and 10% lignin removal. Enzymatic hydrolysis yields of AAGAOP and SEP reached ～90% and ～70%, respectively. Physical‐chemical structural characterization by scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FT‐IR), helped explain the above results. The two methods gave priority to dissociating the guaiacyl lignin and had a relatively small effect on syringyl units. However, AAGAOP exhibited a superior performance. CONCLUSION: The two methods enhanced the enzymatic hydrolysis of lignocellulosic biomass by removing and/or altering physical‐chemical structural impediments. The AAGAOP technique, with some special advantages, was more effective than SEP in enhancing the recovery and enzymatic digestibility of cellulose. Copyright © 2008 Society of Chemical Industry     

木质素对蔗渣酶水解的影响

采用机械活化方法对蔗渣进行处理,研究在原料可及性变化时木质素对蔗渣酶解的影响,用牛血清蛋白（BSA）预先使原料中木质素吸附饱和的方法来测定木质素对酶的吸附情况、用X-射线衍射和扫描电镜来测定蔗渣结晶结构、表面形态来表征原料可及性,从而分析影响的可能机制。结果表明木质素对蔗渣酶水解的影响与蔗渣可及性有关,原料可及性越高,影响越小。当蔗渣可及性相对较低时,此时木质素影响蔗渣酶水解转化率的两种方式（木质素与纤维素、半纤维素组成的致密结构限制纤维素对酶的可及性及木质素对纤维素酶的无效吸附作用）同时存在。当原料的可及性增加到一定程度后（如机械活化2h的蔗渣）,木质素对纤维素酶的吸附作用几乎消除,木质素对蔗渣酶水解的影响主要表现为对酶的可及性的限制。     

Wet oxidation pretreatment of lignocellulosic residues of sugarcane,rice, cassava and peanuts for ethanol production

Wet oxidation (WO) pretreatment of sugarcane bagasse, rice hulls, cassava stalks and peanut shells was investigated. WO was performed at 195 °C for 10 min, with 2 g kg^?1 of Na₂CO₃ and under either 3 or 12 bar of oxygen. Oxygen pressure and the type of raw material used had a major effect on the fractionation of the materials, formation of sugars and by‐products, and cellulose enzymatic convertibility. Cellulose content in the solid fraction increased after pretreatment of all materials, except rice hulls. The greatest increase, from 361 g kg^?1 to almost 600 g kg^?1, occurred for bagasse. The solubilisation of individual components was different for each material. Bagasse xylan was solubilised to a large extent, and 45.2% of it was recovered as xylose and xylo‐oligosaccharides in the liquid fraction. In the prehydrolysates of rice hulls around 40% of the original glucan was recovered as gluco‐oligosaccharides, due to hydrolysis of starch contained in grain remains. The formation of by‐products was modest for all the materials, but increased with increasing oxygen pressure. The highest yield of acetic acid (34–36 g kg^?1 of raw material) and furfural (0.7–1.8 g kg^?1) occurred for bagasse. The pretreatment enhanced the enzymatic convertibility of cellulose giving the best result (670.2 g kg^?1) for bagasse pretreated at the highest oxygen pressure. However, for the other materials the pretreatment conditions were not effective in achieving cellulose conversions above 450 g kg^?1. Some enzymatic conversion of xylan was observed. Copyright © 2007 Society of Chemical Industry     

吐温-80及碱预处理对饲用稻草木质素含量和纤维素酶解产糖的影响

探讨了添加1‰吐温-80非离子表面活性剂和不同浓度碱预处理对稻草秸秆木质素及纤维素的影响,并对预处理前后的稻草进行了X射线衍射光谱(XRD)分析,从结晶度的变化综合分析了预处理对纤维素酶解的影响。实验结果表明:在30℃下添加1‰吐温-80非离子表面活性剂时,用4%NaOH预处理稻草秸秆,木质素含量降至6.5%(较未处理稻草下降了41.9%),灰分值仅占6.9%,具有较好的粗饲料价值;在121℃(0.1 MPa)下添加1‰吐温-80非离子表面活性剂时,用4%NaOH预处理稻草秸秆,木质素含量降至2.8%(较未处理稻草下降了74.5%),酶解还原糖达到393.9 mg/g,纤维素糖化率为59.3%(较未处理稻草提高了2.4倍)。XRD分析显示,在较温和的条件下,低浓度碱预处理稻草秸秆,对纤维素结晶区带来的影响相对于无定形区弱,不足以引起纤维素结晶度的降低。     

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%。     

Ethanosolv pretreatment of barley straw with iron(III) chloride for enzymatic saccharification

BACKGROUND: Barley straw is a potential lignocellulosic biomass for the production of bioethanol because of its high cellulose and hemicelluloses content. Ethanosolv pretreatment catalyzed with inorganic acids has some undesirable effects, and thus, inorganic salts, such as FeCl₃, were studied as the catalyst in order to enhance enzymatic digestibility. RESULTS: The addition of 0.1 mol L^?1 FeCl₃ (Iron(III) chloride) had a particularly strong effect on the enzymatic digestibility, reaching a value as high as 89%, with cellulose recovery as high as 90% after the ethanosolv pretreatment. The enzymatic digestibility was 89% and 55% after the addition of 0.1 mol L^?1 FeCl₃ and H₂SO₄ (adjusted to the same pH), respectively. The enzymatic hydrolysis rate was significantly accelerated as the ethanosolv temperature increased, reaching the highest enzymatic digestibility of 89% after 72 h at 170 °C. The concentrations of HMF(5‐hydroxy‐2‐ methyl furfural) and furfural were 0.011 and 0.148 g L^?1 in the hydrolysate during FeCl₃‐ethanosolv treatment, which were lower than the concentrations quantified during H₂SO₄‐ethanosolv treatment. After the pretreatment, 88.5% of FeCl₃ was removed through the filtration process. CONCLUSION: The addition of several inorganic salts significantly accelerated enzymatic digestibility in the ethanosolv. FeCl₃ had a particularly strong effect on enzymatic digestibility and cellulose recovery. The formation of HMF and furfural and the remaining amount of FeCl₃ were investigated, and FeCl₃ had no effect on the subsequent processes after pretreatment. Copyright © 2010 Society of Chemical Industry     

皇竹草稀硫酸预处理研究

研究了中低温稀酸预处理对皇竹草化学组成变化、纤维素酶水解得率与总糖得率的影响,并采用扫描电镜(SEM)对皇竹草纤维结构变化进行了分析.结果表明,随着硫酸浓度的增大、温度的升高和时间的延长,半纤维素含量大幅度降低,且预处理后纤维素酶水解得率也逐渐增大.较好的预处理条件为100 g皇竹草原料,在固液比1:5(g:mL)条件下,用质量分数4.0%硫酸在温度110 ℃下,经过8 h预处理后,纤维素保留率为87.48%,半纤维素水解率为93.68%,所得固体渣经纤维素酶水解72 h后得率为86.3%(纤维素酶用量40 FPIU/g,以纤维素质量计),100 g原料可得到总糖量为54.53 g.预处理后皇竹草纤维表面和细胞壁受到破坏,表面积增大,有利于纤维素酶水解作用的进行.