氢氧化钠/尿素法和硫酸法测定烟草木质素的对比分析

为了对比氢氧化钠/尿素法(NU法)和硫酸法在测定烟草中木质素含量(质量分数,下同)的差异性,采用NU法和硫酸法测定广东、四川、湖南、云南和贵州5个产区烟梗和烟叶的木质素含量,分析了两种方法在预处理过程的干扰物质去除率及酸解过程木质素含量和结构变化。结果表明:1与硫酸法相比,NU法预处理对干扰物质的去除率更高。2NU法采用稀酸酸解,减少了烟草中木质素的降解;选择在325 nm处测定酸溶木质素(ASL)的紫外吸光度,避免了蛋白质和糠醛对ASL的干扰,提高了烟草木质素测定结果的准确度和重现性。3与硫酸法相比,NU法分离得到的酸不溶木质素(AIL)的氧化程度低、结构变化小,因而更能反映烟草木质素的结构特征。NU法比硫酸法更加适用于烟草木质素的含量测定。     

竹溶解浆的碱预处理及其溶解性能研究

选用聚合度为1228的商品竹溶解浆为原料,通过偏光显微镜、纤维素溶液紫外-可见光（UV-Vis）光谱、动态光散射（DLS）和透射电镜（TEM）分析及溶解率测定研究了经不同浓度NaOH（质量分数1%～12%）预处理后的竹溶解浆在7%NaOH/12%尿素水溶液溶剂体系中的低温溶解行为。结果表明,适宜浓度碱液的预处理提高了纤维素的反应活性及7%NaOH/12%尿素水溶液溶剂对竹溶解浆纤维素的可及度,其中,9% NaOH预处理后的竹溶解浆表现出最佳的溶解效果。     

NaOH/尿素溶液中纤维素稳态流变性的浓度依赖性

为优化纤维素的纺丝条件,研究了纤维素在NaOH/尿素水溶液中的稳态流变性能。结果表明,不同质量浓度的纤维素在NaOH/尿素水溶液中都表现出假塑性流体的性质,非牛顿指数随着纤维素质量浓度的增加而下降,表观黏度和稠度系数则随其质量浓度的增加而增加。此外,纤维素在NaOH/尿素水溶液中的质量浓度变化对溶液的结构黏度影响较大,纺丝适宜质量浓度为4%-5%。     

蒸汽爆破技术在烟梗加工中的应用

为了提高烟梗的利用率,在梗丝生产线的不同工序顺序取样进行蒸汽爆破试验,研究了爆破前后各工序梗丝中的木质素、纤维素含量变化及添加爆破梗丝对卷烟的感官品质影响。结果表明:①原梗丝生产线对烟梗中的纤维素、半纤维素和木质素含量无显著影响,但蒸汽爆破后烟梗中的纤维素、半纤维素和木质素含量显著降低。半纤维素的含量降低最多,切梗后含量降低了49.5%。纤维素和木质素的含量变化没有半纤维素明显,但其最大降幅也分别达到了26.5%(润梗后)和26.0%(闪蒸后)。②蒸汽爆破梗丝在卷烟中的添加量从5%增加到30%时,试验卷烟样品仍保持较好的感官品质。     

利用微生物降解烟梗中细胞壁物质的响应曲面优化

细胞壁物质对烟梗抽吸品质有不利影响,为研究微生物发酵液对降解烟梗中细胞壁物质的作用效果,采用二因素三水平的响应曲面法优化了微生物发酵液添加量和处理时间对降解烟梗中纤维素、果胶、木质素较佳工艺条件。结果表明,微生物发酵液能有效降低烟梗中的细胞壁物质,发酵液添加量比处理时间作用效果更加显著,建立的二次回归模型均达到了显著性水平,能客观地描述发酵液添加量、处理时间与各响应值之间的关系。经优化,利用微生物降解烟梗中细胞壁物质的较佳工艺条件为发酵液添加量66.7 m L/kg、处理时间180 min,在优化条件下烟梗中纤维素、果胶、木质素含量较未处理烟梗分别降低了12.78%,8.77%和33.55%。     

低温NaOH溶液中低聚合度纤维素的溶解与析出

采用浓度为9%的NaOH溶液在低温条件下对木浆纤维素进行润胀溶解,分别测定原料和不溶纤维素的R-10值、聚合度,并采用红外光谱(FTIR)、扫描电镜(SEM)、热重(TG)以及X-射线衍射(XRD)方法对原料、不溶纤维素和水析出纤维素进行表征。结果表明低温有利于纤维素在NaOH溶液中的溶解,且在实验设计的范围内温度越低,低聚合度纤维素溶解得越多。与原料和不溶纤维素相比,水析出纤维素的热稳定性稍差。低温条件下,纤维素I晶型易转变为纤维素II晶型,同时析出纤维素也表现出纤维素II晶型。析出纤维素表面孔隙多、表面积大,有可能制备成吸附、隔音或保温材料。     

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。     

饲用稻草预处理的研究

采用高温高压、稀碱液、液氨对稻草粉进行预处理,并模拟猪胃环境对预处理效果进行了比较。结果表明,预处理能提高稻草纤维素的糖化率,其中稀碱处理较其它处理效果要好。同时稀碱处理使稻草中半纤维素和木质素大量溶出,随着碱液浓度的增大,半纤维素损失显著上升。通过稀碱处理正交实验发现,固液比对酶解率影响最大,NaOH浓度对半纤维素的溶出影响最大,初步确定最佳处理碱质量分数为1.5%,以低温处理效果较好,最终酶解率达73.5%,半纤维素损失率33.1%。     

超临界CO_2处理玉米秸秆残留木质素形态及脱除研究

基于玉米秸秆纤维素酒精的原料预处理中残留木质素阻碍纤维素酶解的难题。本研究以超临界CO_2流体的预处理过程难以脱除的残留木质素为研究对象,采用SEM、ATR-FTIR、XPS等手段对残留木质素存在形式进行了考察,分析残留木质素难以脱除的原因,在此基础上,探讨了不同洗涤方法对于残留木质素的脱除效果。预处理后难以脱除的残留木质素以球状颗粒形式不均匀分布在纤维素表面,颗粒直径在0.1~0.9μm。同时分别采用乙醇水和氢氧化钠等洗脱方法对残留木质素进行脱除,研究发现两种洗脱方法均能有效脱除纤维素表面的残留木质素,但与乙醇水溶液相比,NaOH溶液的洗脱效果更好。     

高沸醇溶剂法提取烟梗中木质素的研究

以1,4-丁二醇水溶液为溶剂,采用高沸醇溶剂法从烟梗中提取木质素.其最佳提取条件为:烟梗原料50 g(干质量),采用1,4-丁二醇水溶液(V(醇)∶V(水)=9∶1),固液比(g∶mL)为1∶10,加入少量浓H2SO4作为催化剂,在220℃下对烟梗进行蒸煮2 h,木质素收率最高.采用紫外光谱和红外光谱对其结构进行表征,结果表明,高沸醇溶剂法提取的烟梗木质素具有木质素类化合物的典型结构特征.     

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%。     

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。     

乙酸脱除天然竹纤维木质素的研究

以慈竹为研究对象,对常压下乙酸脱除天然竹纤维中的木质素进行了探讨。以反应温度、乙酸体积分数、催化剂硫酸体积分数和反应时间为单因子,考察这些因素对天然竹纤维木质素脱除率的影响。结果表明:影响因素从大到小依次为反应温度、催化剂硫酸体积分数、乙酸体积分数和反应时间。正交试验结果表明,乙酸在脱除天然竹纤维木质素的过程中也脱除了部分半纤维素和纤维素。结合木质素脱除率、半纤维脱除率和纤维素脱除率,得到了最佳工艺条件,即90℃,乙酸体积分数88%,硫酸体积分数0.3%,反应时间3 h,在该条件下木质素的脱除率达到55.84%。     

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.     

Inter-relationships between acidic and alkali treatments of cotton straw and wheat straw and their fibre chemical properties

The amount of lignin in the cell walls of cotton straw (CS) and wheat straw (WS) was found to be the same, but the ratio between lignin and hemicellulose was considerably lower in CS than in WS. In CS the amount of soluble acid lignin was less than 1% of the total lignin, whereas in WS it was 20%. The amount of phenolics in concentrated sulphuric acid (72%) hydrolysates of the cell wall was reduced drastically in WS compared with the amount released by diluted (1 N) sulphuric acid; this may have been due to polymerisation of low-molecular-size lignin. The amount of alkali-soluble lignin in WS was 3–7 times greater than in CS. Following acid treatment the amount of alkali-soluble lignin was reduced from 20% of the total content to 5% in WS, and from 5% to 1% in CS. Enzymic hydrolysis was 49% higher in WS cell wall than in CS cell wall. In WS, acidic and alkali pretreatments followed by cellulase treatment increased glucose yield from cellulose by 260% and 280%, respectively. In CS, acidic pretreatment did not affect the glucose yield from cellulose, whereas alkali treatment increased it by 35%.     

Dietary Fiber in Spanish Fruits

The dietary fiber, cellulose, hemicellulose, lignin and pectic substances of 21 fruits have been determined. For some of these fruits several varieties and different degrees of ripeness have been considered. The contents of these compounds ranged between 0.2– 2.75% for dietary fiber, 0.06–1.8% for cellulose, 0.00–0.86% for hemicellulose, 0.06–0.5% for lignin and 0.12–1.28% for pectic substances. In some cases the dietary fiber can be affected by the fruit variety. Plantain increased in dietary fiber, hemicellulose and pectic substances content with increased ripening, while no change in cellulose and a decrease of lignin content were observed.     

Agriculture group symposium agriculture and pollution

The digestion of carbohydrates in straw and their substituent acetic and phenolic acids was studied using a slaughter technique. Two goats received non-alkali-treated and alkali-treated straws. The latter treatment increased the total apparent digestibility of cellulose by 56% and of hemicellulose by 110%. The ratio of cellulose to hemicellulose was altered in the rumen. For the non-alkali-treated straw the ratio decreased compared with the feed, whereas it increased for the alkali-treated straw. The ratio was kept almost constant post-rumen for both diets. The composition of the hemicellulose was also altered in the rumen compared with the straws fed. In particular the arabinose content decreased in both diets. Most of the polysaccharide digestion and absorption took place in the rumen. For the alkali-treated straw a hindgut fermentation could also be noted, especially for cellulose. Klason lignin was lost in the rumen but was recovered in the small intestine. Ferulic acid was more readily lost in the rumen than p-coumaric acid. Although acetyl groups were almost absent in the alkali-treated straw, they could still be found in the digesta of the animal. The slaughter technique appears to be a useful method when working with partitioning of digesta in ruminant animals.     

制取可降解纤维地膜的秸秆纤维特性研究

原料的特性在很大程度上决定了产品的特性及加工工艺,因此对制成可降解纤维地膜的原料秸秆纤维进行物理化学及机械打浆特性研究具有重要意义。本研究采用Leica显微镜测定秸秆纤维形态,SPSS17．0统计分析纤维长宽比,Design-expert6．0．10区组对比分析两种秸秆、纤维间理化及机械打浆特性差异和经机械加工后纤维成...     

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。