Non-thermal plasma as an innovative pretreatment technology in delignification of brewery by-product

Non-thermal plasma was applied as an innovative pretreatment for the delignification of brewery by-products. The influence of different plasma gases (pure air or air/argon), time and solids concentration (7.5, 10 and 12.5%) was evaluated during the delignification tests. The levels of cellulose, hemicellulose and lignin were monitored before and after treatment. The reduction in lignin content was approximately 50% after 5 min using pure air in all tested solids concentrations. Longer pretreatment times (60 min) influenced the removal of hemicellulose (50%) and cellulose (12%), also indicated by morphological changes. After 5 and 60 min of plasma application, the physical-chemical characteristics showed minor changes in its chemical composition, mainly affected by the losses of lignocellulosic compounds. Non-thermal plasma is considered an attractive alternative for the pretreatment of brewery by-products, resulting mainly in removing lignin, assisting in subsequent processes such as the enzymatic hydrolysis of the spent solid.     

NaOH/尿素低温溶解法测定烟梗木质素含量的研究

建立了一种准确测定烟梗木质素含量的新方法。用低温NaOH/尿素水溶液抽提烟梗,采用优化的酸处理条件（硫酸浓度17.5 %、液固比80 mL?g-1、酸解温度100 ℃、酸解时间30 min）打断烟梗中木质素与纤维素等组份之间的化学键,残渣用低温NaOH/尿素水溶液进一步溶解纤维素、半纤维素等天然高分子物质,得到酸不溶木质素。酸溶木质素采用分光光度法在325 nm处测定,酸不溶木质素采用灼烧法测定。本方法RSD小于3%,准确度良好,且减少了有机溶剂预处理和浓硫酸处理,提高了测试的安全性。      

液氨爆破对稻草秸秆稀硫酸降解工艺影响

为给制取生物质乙醇提供参考,该实验对木质纤维原料进行液氨爆破预处理后稀硫酸降解工艺进行研究。以农产秸秆为原料,自制爆破装置,采用化学分析与扫描电镜、X射线衍射相结合方法,分别研究液氨爆破在温度60℃～80℃、维压时间10～30 min、压力1.0～4.0 MPa条件下,液氨爆破预处理对秸秆主要成分与稀硫酸水解还原糖得率影响。结果表明,当液氨爆破条件为温度70℃、时间20 min、压力2.5 MPa时,处理后物料纤维素含量35.99%、半纤维素含量16.71%、稀硫酸水解还原糖得率最高达38.83%;SEM与XRD显示,液氨爆破后稻草秸秆纤维形态结构受到不同程度破坏,表面断裂、空隙增加、纤维素结晶度降低,有利于稀酸水解作用。     

氨纤维爆破法预处理木质纤维生物质原料

生物质预处理的目的是使紧密的原料组织变得疏松,以增加酶催化作用的表面积。氨纤维爆破(AFEX)是一种应用物理(高温高压)化学(氨水)工艺实现高效处理的方法。木质纤维素经AFEX预处理后,其纤维素结晶度降低,部分半纤维素解聚,木质素部分分解游离,原料表面水解特性增加。AFEX预处理和稀酸预处理相比减少了中和、脱毒等工艺,还可以减少发酵工艺中氮源的添加,因而作为一种新技术越来越受到重视。     

蒸汽与液氨爆破对白酒丢糟稀硫酸降解工艺的影响研究

以白酒厂丟糟为原料,自制爆破装置,采用化学分析与扫描电镜、X射线衍射相结合的方法,分别研究了蒸汽爆破在温度200℃～220℃,维压时间5min～20min,压力1.0MPa～4.0MPa;液氨爆破在温度60℃～80℃,维压时间10min～30min,压力1.0MPa～4.0MPa的条件下,蒸汽与液氨爆破预处理对丢糟的主要成分与稀硫酸水解还原糖得率的影响。结果表明,当蒸汽爆破条件为温度210℃,时间10min,压力2.5MPa时,处理后物料纤维素含量33.42%,半纤维素19.03%,稀硫酸水解还原糖得率最高51.92%;当液氨爆破条件为温度70℃,时间30min,压力2.5MPa时,处理后物料纤维素含量19.01%,半纤维素32.45%,稀硫酸水解还原糖得率最高48.09%。SEM与XRD显示,蒸汽与液氨爆破后白酒丢糟纤维形态结构受到不同程度的破坏,表面断裂、空隙增加,纤维素的结晶度降低,有利于稀酸水解作用的进行。     

木质素与半纤维素对稻草秸秆酶解的影响

分别采用稀酸和酸碱顺序两种方法处理稻草秸秆,20 FPU/g(底物干重)的纤维素酶、底物质量浓度为80 g/L,45℃酶解72 h。结果表明,木质素与半纤维素对纤维素转化为葡萄糖都有较大影响,稀酸处理的秸秆酶解纤维素转化率(43.4%,葡萄糖质量浓度24.1 g/L)是未处理秸秆(16.8%,葡萄糖质量浓度6.2 g/L)的2.6倍,而酸碱顺序处理的秸秆(60.6%,葡萄糖质量浓度47.7 g/L)则是未处理秸秆的3.6倍。采用上述两种方法处理秸秆后,秸秆木质素和半纤维素被移去,秸秆结构发生改变,从而秸秆纤维更易受纤维素酶的攻击,并且秸秆木质素和半纤维素质量分数越低,纤维素的酶解得率就越高。     

Lignin Interaction with Cellulase during Enzymatic Hydrolysis

The conversion of lignocellulosic biomass into biofuels or biochemicals typically involves a pretreatment process followed by the enzyme-catalyzed hydrolysis of cellulose and hemicellulose components to fermentable sugars. Many factors can contribute to the recalcitrance of biomass, e.g., the lignin content and structure, crystallinity of cellulose, degree of fiber polymerization, and hemicellulose content, among others. However, nonproductive binding between cellulase and lignin is the factor with the greatest impact on enzymatic hydrolysis. To reduce the nonproductive adsorption of enzymes on lignin and improve the efficiency of enzymatic hydrolysis, this review comprehensively summarized the progress that has been made in understanding the interactions between lignin and enzymes. Firstly, the effects of pretreatment techniques on lignin content and enzymatic hydrolysis were reviewed. The effects of lignin content and functional groups on enzymatic hydrolysis were then summarized. Methods for the preparation and characterization of lignin films were assessed. Finally, the methods applied to characterize the interactions between lignin and cellulase were reviewed, and methods for decreasing the nonproductive binding of enzymes to lignin were discussed. This review provides an overview of the current understanding of how lignin hinders the enzymatic hydrolysis of lignocellulosic biomass, and provides a theoretical basis for the development of more economical and effective methods and additives to reduce the interaction of lignin and enzymes to improve the efficiency of enzymatic hydrolysis.     

Hydrothermal Pretreatment of Lignocellulosic Materials for Improving Bioethanol Production

With the continued depletion of non-renewable energy resources,it is essential to seek new methods of harnessing clean and renewable energy.In this regard,second-generation bioethanol derived from lignocellulosic biomass has attracted increasing attention in recent years.The choice of the pretreatment method of lignocellulose is critical to the subsequent bioconversion processes.Compared with other conventional chemical pretreatment methods,hydrothermal pretreatment is a simple,low-cost,and economically feasible process that requires water as the only reagent.This paper reviews the research efforts that have been made toward hydrothermal pretreatment of lignocellulosic biomass and focuses on the transformations involving cellulose,hemicellulose,and lignin during this process.     

无机金属盐和过氧化物对酸处理玉米秸秆纤维素和半纤维素降解的影响

纤维质物料的预处理是木质纤维素原料发酵生产燃料乙醇的关键步骤。使用加入无机盐和H2O2的稀酸溶液处理玉米秸秆,并考察其对纤维素和半纤维素降解的影响,同时测定了相应的降解速率和处理强度（R）。结果表明,无机盐和H2O2的存在提高了玉米秸秆半纤维素的降解程度和降解速率,促进了半纤维素的单糖转化率,但对纤维素的降解影响不大。通过条件优化,当R值为0．2时,木糖回收率最高达85％,而纤维素得到了有效的保留,损失率不超过10％。     

从木素物理性质比较AP及AS预处理对红麻秆芯部的作用

以红麻秆芯及经过碱性过氧化氢预处理（ＡＰ）和碱性亚硫酸钠预处理（ＡＳ）后的红麻秆芯为研究对象,分离出磨木木素,并从相对分子质量及其分布、玻璃化转移温度等方面研究了３种磨木木素的物理性质的差异。同时研究了３种料片的弹性模量同温度的关系。研究认为,在本实验条件下,ＡＳ预处理对红麻秆芯的性质有显著的作用,是制备化学机械浆较好的预处理方法;而ＡＰ预处理,对红麻秆芯的作用程度较弱。     

Physicochemical and Morphological Variation of Bamboo Cell Wall During Hydrothermal Pretreatment

Pretreatment is important for achieving high-value utilization of biomass. This study is conducted to evaluate the destruction of the Moso bamboo cell wall via hydrothermal pretreatment at different temperatures and pH values. Compositional and morphological analyses and subsequent enzymatic hydrolysis of the solid fractions indicate that the destruction of the cell wall, instead of the degradation or removal of hemicellulose and lignin, or the configuration transition of the cellulose crystal structure, is the most critical aspect for improving bioconversion efficiency. Although only an 8%-10% weight loss is incurred and similar crystalline indexes are achieved after mild hydrothermal treatments, the recovery of glucose is doubled, whereas the recovery of xylose from pretreated samples is approximately 35%.     

硬毛粗盖孔菌预处理对玉米秸秆酶水解及组分变化的影响

以硬毛粗盖孔菌（Funalia trogii）为研究对象,比较其在不同预处理时间的产酶特征、预处理前后玉米秸秆酶解产糖量及其组分变化。结果表明,硬毛粗盖孔菌对木质素的降解以漆酶和锰过氧化物酶的协同作用为主导,漆酶和锰过氧化物酶活最高分别为341 IU/g和33 IU/g。经生物预处理14 d后的玉米秸秆酶解产糖量可达到350.74 mg/g秸秆,较原料提升184%。玉米秸秆组分的变化与其酶解增效密切相关,F. trogii预处理14 d后木质素和半纤维素含量分别降低了33.99%和36.61%,而纤维素仅降解8.77%,木质素和半纤维素的选择性降解,可显著降低玉米秸秆酶解抗性屏障,提升其酶解糖化效率。硬毛粗盖孔菌预处理玉米秸秆可实现木质纤维素的高效转化,缩短预处理时间,降低处理成本。     

Chemical composition of some forages and various residues from feeding value determinations

NDF, ADF, ‘cellulose’ and IVOMD residues, from feeding value determinations, were prepared from some forages, including straw, alkali-treated straw, grass and lucerne samples. The crude protein, cellulose, hemicellulose, uronic acid, Klason lignin, lignin and ash contents of these residues and the corresponding original forage samples were determined together with the relative composition of the neutral sugar constituents after acid hydrolysis. Cellulose, hemicellulose and Klason lignin were the main components in the NDF fractions but substantial amounts of crude protein (1–6%) also remained. Cellulose and Klason lignin were the main components in the ADF fractions, but 7–14% of the fractions was hemicellulose and 1–4% crude protein. Cellulose was the main component in the ‘cellulose’ fractions, but they also contained 8–13% hemicellulose, 2–7% Klason lignin and 2–11% ash. The composition of the IVOMD residues showed that cellulose and hemicellulose had been dissolved to about the same amounts (70–80%) and that most of the Klason lignin remained.     

Influence of various retting methods on properties of kenaf fiber

Gum, as the important noncellulosic tissue present in kenaf fiber, has a close relation with downstream processing and product properties, so the predominant task in pretreatment of kenaf fiber for textile application, retting, is to remove gum including pectin, hemicellulose, lignin, and other impurities without damage to cellulose fiber. The traditional retting method is water retting; that is, the harvested kenaf bast is soaked in natural water (rivers or tanks) in which indigenous bacteria attack the gum in an anaerobic process, yielding much water pollution. Currently, much interest has been focused on various retting methods in order to seek one environmentally-friendly method. Therefore, microbe, chemical, water, and microbe–chemical rettings are performed in this experiment. Retted kenaf fibers at optimal conditions of various retting methods are then characterized and compared by light microscopy and indices consisting of residual gum content, fineness, tenacity, elongation, and softness. In addition, chemical oxygen demand (COD) is also tested. The results indicate that microbe retting induces higher residual gum content and lower elongation but better tenacity and softness and finer fiber; chemical retting gives lower tenacity and thicker fiber; water retting produces weak, poor quality fiber; and microbe–chemical retting produces moderate indices.     

稀酸预处理对玉米秸秆纤维组分及结构的影响

研究了稀硫酸预处理对玉米秸秆化学组成变化及纤维素酶水解得率的影响,并采用扫描电镜(SEM)、X射线衍射仪(XRD)、红外光谱(IR)和热重分析(TG)对玉米秸秆纤维结构特性进行了分析。结果表明随着硫酸浓度的增大、温度的升高和时间的延长,纤维素和木质素含量有所增加,而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。当处理条件为硫酸质量分数0.75%、温度150℃、时间80 min时,半纤维素降解率为98.02%,所得固体渣纤维素酶水解得率为66.95%(纤维素酶用量20 FPUI/g纤维素)。稀酸预处理后玉米秸秆纤维表面和细胞壁受到不同程度的破坏,表面积增大,孔洞增加,纤维素的结晶度降低,有利于纤维素酶水解作用的进行。     

Degradation of wood surfaces by water

Weight losses and ultrastructural and chemical changes in pine and lime following exposure to deionised water in the temperature range 60° C–90° C are examined. Similar weight losses of 10% occur in pine and lime strips after 100 days exposure to water at 60 and 70° C but at 80 and 90° C lime shows greater weight losses (30%) than pine (15%). Observations of transverse surfaces exposed to water at 90° C for 50 days revealed separation of the secondary wall from the compound middle lamella region and some separation of individual cells. Chemical analysis of pine and lime wood flour exposed to deionised water at 65° C for 50 days revealed losses of hemicelluloses and lignin with little loss in cellulose. Changes in hemicellulose composition are thought to result primarily from degradation of pectinacious polysaccharides. Losses in lignin and hemicellulose were higher and lower respectively in lime than in pine. Viscometry measurements on cuprammonium dispersions of holocellulose isolated from hot water exposed pine strips indicate that little depolymerisation of cellulose occurs. It is suggested that the chemical and ultrastructural changes noted here accord with the losses in wet tensile strength and toughness of hot water exposed thin wood strips and failure of these particularly in lime by inter-fibre shear.     

Evaluation of pretreatment with Pleurotus ostreatus for enzymatic hydrolysis of rice straw

The effects of biological pretreatment of rice straw using four white-rot fungi (Phanerochaete chrysosporium, Trametes versicolor, Ceriporiopsis subvermispora, and Pleurotus ostreatus) were evaluated on the basis of quantitative and structural changes in the components of the pretreated rice straw as well as susceptibility to enzymatic hydrolysis. Of these white-rot fungi, P. ostreatus selectively degraded the lignin fraction of rice straw rather than the holocellulose component. When rice straw (water content of 60%) was pretreated with P. ostreatus for 60 d, the total weight loss and the degree of Klason lignin degraded were 25% and 41%, respectively. After the pretreatment, the residual amounts of cellulose and hemicellulose were 83% and 52% of those in untreated rice straw, respectively. By enzymatic hydrolysis with a commercial cellulase preparation for 48 h, 52% holocellulose and 44% cellulose in the pretreated rice straw were solubilized. The net sugar yields based on the amounts of holocellulose and cellulose of untreated rice straw were 33% for total soluble sugar from holocellulose and 32% for glucose from cellulose. The SEM observations showed that the increase in susceptibility of rice straw to enzymatic hydrolysis by pretreatment with P. ostreatus is caused by partial degradation of the lignin seal. When the content of Klason lignin was less than 15% of the total weight of the pretreated straw, enhanced degrees of enzymatic solubilization of holocellulose and cellulose fractions were observed as the content of Klason lignin decreased.     

嗜碱性木素降解菌降解能力的初步研究

通过比较不同嗜碱细菌对麦草中木素、纤维素和半纤维素的降解率, 并比较不同菌株的产酶及酶活情况, 筛选出了木素降解能力较强, 而纤维素和半纤维素降解能力相对较弱的嗜碱性木素降解菌。在ｐＨ≈１０－４的条件下培养８ｄ 后, 菌株６ 降解了３２－３７％ 的麦草木素, 而纤维素和半纤维素分别降解了２１－４８％ 和２２－６９％ 。这与其产酶情况基本一致, 该菌株的酶活最高, 分别为ＭｎＰ２７１－３０Ｕ／Ｌ和ＬｉＰ４１－９４Ｕ／Ｌ。     

稻草酸水解制还原糖的工艺条件

研究了用稀H2SO4直接酸解稻草制还原糖的最佳条件,探讨了酸浓度、酸解温度和酸解时间等因素对还原糖含量的影响。实验表明,用稀H2SO4直接酸解稻草省去了预处理步骤,能获得较大的还原糖收率。采用正交实验法,以总还原糖浓度为考察指标,对实验结果进行方差分析,得出稀H2SO4酸解稻草的最适宜工艺条件为:硫酸质量分数20%,水解温度60℃,水解时间36h,稻草与硫酸量比为1∶10,可获得还原糖浓度为23.835g/L。对于稻草水解过程,认为4h前主要为半纤维素水解,16～36h主要为纤维素水解,36h后水解基本完成。     

Box-Behnken法优化玉米秸秆预处理工艺对酶解糖化的影响

为促进生物炼制产业发展,提高玉米秸秆酶解糖化效率,运用Box-Behnken试验设计优化预处理工艺,研究硫酸质量分数、反应时间、反应温度和固液比四个因素对半纤维素水解率的影响规律,并结合扫描电子显微镜、红外光谱仪、X-射线衍射仪分析玉米秸秆微观形貌、结构等指标。结果表明：玉米秸秆预处理最佳工艺为反应温度100℃、硫酸质量分数1.2%、反应时间120 min、固液比1∶9（g∶mL）,在此条件下半纤维素水解率为84.93%,木质素脱除率为46.15%,预处理水解液还原糖质量浓度为2.04 g/100mL,木糖产率为74.22%,87.89%纤维素保留在固体部分,经72 h酶解反应酶解率达到85.79%,未处理玉米秸秆酶解率仅为32.25%。