低聚合度木聚糖对木聚糖酶合成的影响

研究了木聚糖的聚合度和添加黄豆粉对里氏木霉合成木聚糖酶的影响,并以纯化木聚糖酶水解木聚糖。研究结果表明:木聚糖经酶水解后平均聚合度降低54%,戊聚糖含量为75.4%。采用低聚合度木聚糖为底物碳源和添加黄豆粉都可提高产酶效果。以12g/L低聚合度木聚糖添加2g/L黄豆粉,培养3d后木聚糖酶活力可达到113IU/mL,提高49.3%。通过对木聚糖酶进行纯化处理可以有效除去β 木糖苷酶。以体积分数10%的木聚糖酶水解35g/L木聚糖3h后,低聚木糖得率达到35.5%,而木糖得率仅为1.5%,低聚木糖与总糖的比值达到95.8%,随着酶解时间的延长,低聚木糖不会被降解。     

低聚木糖生产用木聚糖酶的选择性合成

以里氏木霉(Trichoderma reesei)Rut C-30为产酶菌,研究了碳源、碳氮比对木聚糖酶酶系组成的影响.低分子量组分较多的木聚糖有利于促进内切-β-木聚糖酶的合成,酶解产物中低聚木糖的含量较高(80.70%).低碳氮比有利于促进内切-β-木聚糖酶的合成,抑制外切-β-木糖苷酶的合成.以低分子量较多的木聚糖(7g/L)为碳源,降低培养基的碳氮比为4.0,调控培养60h,用该木聚糖酶酶解粗木聚糖,产物中低聚木糖占总糖的86.32%.     

低聚合度木聚糖对木聚糖酶合成的影响

研究了木聚糖的聚合度和添加黄豆粉对里氏木霉合成木聚糖酶的影响，并以纯化木聚糖酶水解木聚糖。研究结果表明：木聚糖经酶水解后平均聚合度降低54％，戊聚糖含量为75．4％。采用低聚合度木聚糖为底物碳源和添加黄豆粉都可提高产酶效果。以12g／L低聚合度木聚糖添加2g／L黄豆粉，培养3d后木聚糖酶活力可达到113IU／mL，提高49．3％。通过对木聚糖酶进行纯化处理可以有效除去β-木糖苷酶。以体积分数10％的木聚糖酶水解35g／L木聚糖3h后，低聚木糖得率达到35．5％，而木糖得率仅为1．5％，低聚木糖与总糖的比值达到95．8％，随着酶解时间的延长，低聚木糖不会被降解。     

超声-酶法水解小麦麸皮制备低聚木糖的研究

小麦麸皮是小麦加工处理后副产物,仍保有大量的营养成分,但并未得到良好的利用。以小麦麸皮为原料,通过超声辅助提取-酶法制备低聚木糖,考察了超声功率和超声时间对小麦麸皮木聚糖组分提取的影响,通过加酶量、底物质量分数和水解时间等3个因素考察了酶法制备低聚木糖的条件。当超声功率为1200W、超声时间为30 min、木聚糖添加量(质量分数)为8%、加酶量为10 U/g和酶解时间为6 h时,低聚木糖产量为14.13 g/L。     

Thermoanaerobacterium saccharolyticum JW/SL-YS485来源的GH11家族木聚糖酶的克隆表达及其应用

对Thermoanaerobacterium saccharolyticum JW/SL-YS485来源的GH11家族木聚糖酶基因xyn11进行了克隆表达研究。xyn11基因全长636bp,编码211氨基酸。通过构建重组质粒,使其在大肠杆菌中实现了活性表达,酶活达到13.8U/mL。重组酶通过热处理和Ni亲和层析达到电泳纯,SDS-PAGE显示其分子量为20000,与理论分子量吻合。重组酶的最适反应温度为65℃,最适反应pH为4.5,在pH 3.5~6.0范围内保持较高的稳定性,60℃保温1h,酶活还残存60%,Cu²⁺对该酶有激活作用。重组酶底物特异性强,且不能降解木二糖和木三糖。重组酶以榉木木聚糖为底物,其V_max和K_m分别为9809U/mg和5.9mg/mL。榉木木聚糖质量浓度为25g/L,重组木聚糖酶用量为20U/g,在50℃、pH 4.5条件下水解12h低聚木糖的得率为27.8%,水解产物主要由木二糖和木三糖组成,且不产生任何木糖。结果表明,该木聚糖酶催化特性优异,可用于低聚木糖的制备。     

-木糖苷酶的分离纯化、酶学性质及水解机理研究

通过硫酸铵沉淀、超滤脱盐、离子交换层析、凝胶过滤层析等手段,从里氏木霉(Trichoderma reesei)Rut C-30木聚糖酶粗酶液中分离纯化得到分子质量110.8 ku、比活力为61.99 IU/mg的电泳纯β-木糖苷酶。酶学性质研究结果表明:该酶反应以温度60 ℃、pH值3.5为宜,在60 ℃以下、pH值3.0～8.0酶活性稳定,且该酶作用于对硝基苯基-β-D-木糖苷的K_m值和V_max值分别为0.29 μmol/mL和169.99 IU/mg。酶水解机理研究结果表明,该酶从低聚木糖的非还原性末端切断β-1,4-糖苷键释放出木糖,其最适作用底物是短链的低聚木糖,随着低聚木糖碳链的增长,酶作用效率逐渐下降,而对木聚糖几乎不降解。     

以秸秆为原料制备低聚木糖工艺研究

研究了稻草粉经氯化钠预处理后加氧氧化钠高温蒸煮提取木聚糖,然后再加酶水解生产低聚木糖的工艺路线.稻草粉在质量分数为2.5%的NaCl溶液中浸泡12 h后,滤去浸泡液,然后采用固液比1∶10、120℃、120 min的蒸煮条件进行蒸煮.结果表明,木聚糖的提取得率达29.05%(按稻草粉中木聚糖计),用底物质量分数为3%的木聚糖,加入木聚糖酶液,水解温度80℃,反应时间5 h,最后测得还原糖总质量浓度可达3.54g/L.     

木聚糖酶在制备低聚木糖中的应用进展

低聚木糖(Xylo-oligosaccharide,XOS)是一类由木糖分子连接而成的益生元化合物,具有促进双歧杆菌的生长、改善肠道菌群的组成结构、提高人体免疫力以及预防疾病等功能特性.酶法是较适合的XOS制备方法.简要阐述了木聚糖和XOS的结构,并对XOS降解酶系中木聚糖酶的结构、作用位点和酶系分类以及在制备低聚木糖中的应用进行详细介绍.重点探讨了木聚糖酶GH10和GH11家族对XOS产物的影响,以及重组和固定化木聚糖酶及复合酶法中不同类型木聚糖酶的结合使用在XOS制备中的应用,对XOS产物的影响进行了阐述.旨在为XOS的制备及应用提供理论依据,并为XOS构效关系的深入研究奠定基础.     

木聚糖生物转化药物、能源和化工中间体

介绍了木聚糖的结构与酶糖化机理,综述了国内外对木聚糖生物转化方面的研究.详细介绍了木聚糖转化为低聚木糖和木糖醇等医药食品、燃料乙醇和2,3-丁二醇等能源物质、乳酸和糠醛等化工中间体的研究进展.     

低聚壳聚糖的复合酶法制备研究

通过对黏均分子量、酶活力、水解率和还原糖浓度的测定,研究了由商业α-淀粉酶、纤维素酶和果胶酶1∶1∶1(m/m/m)组成的复合酶降解壳聚糖的最佳工艺条件,结果表明:复合酶在酶底物比为1∶5(m/m)、pH 5.3、温度56℃的条件下,酶解2 h可得到分子量为1 000～4 000的低聚壳聚糖,且通过傅里叶红外光谱分析酶解后的产物结构无明显变化。     

18C型肺炎球菌荚膜多糖的水解及水解片段的特性

目的探索不同乙酸水解条件对18C型肺炎球菌多糖的水解效果。方法选择60℃和92℃2种温度,以不同乙酸浓度和不同时间对多糖进行水解,用层析法检测相对分子质量,免疫双扩散法和ELISA抑制法分别检测活性。结果0.2mol/L乙酸92℃水解16h,水解程度趋于稳定,相对分子质量可达57000;1.0mol/L乙酸60℃水解40h,水解程度趋于稳定,相对分子质量可达235000;用1.0mol/L乙酸在不同温度下水解时,随着温度升高,水解程度增加,而在92℃不同乙酸浓度对水解程度几乎无影响。上述条件所得水解片段均保留了抗原性,但随着相对分子质量的降低,抗原性有所减弱。结论在不同条件下,乙酸能将18C型肺炎球菌荚膜多糖水解为不同大小的片段,且未破坏抗原决定簇的基本结构。     

Optimization of glutamine Peptide production from soybean meal and analysis of molecular weight distribution of hydrolysates

The process parameters of enzymatic hydrolysis and molecular weight distribution of glutamine (Gln) peptides from soybean meal were investigated. The Protamex^® hydrolysis pH of 6.10, temperature of 56.78 °C, enzyme to substrate ratio (E/S) of 1.90 and hydrolysis time of 10.72 h were found to be the optimal conditions by response surface methodology (RSM) for a maximal degree of hydrolysis (DH) value of 16.63% and Gln peptides content at 5.95 mmol/L. The soybean meal was hydrolyzed by a combination of Protamex^® and trypsinase so that DH and Gln peptides would reach 22.02% and 6.05 mmol/mL, respectively. The results of size exclusion chromatography indicated that the relative proportion of the molecular weight <1000 Da fraction increased with DH values from 6.76%, 11.13%, 17.89% to 22.02%, most notably the 132–500 Da fractions of hydrolysates were 42.14%, 46.57%, 58.44% and 69.65%. High DH values did not lead to high Gln peptides content of the hydrolysate but to the low molecular weight Gln peptides.     

低分子量聚N-乙烯基甲酰胺-co-乙烯胺的合成

以N-乙烯基甲酰胺为单体,N,N-二甲基甲酰胺和乙酸乙酯为混合溶剂,偶氮二异丁腈为引发剂,十二硫醇为链转移剂,通过沉淀聚合法制备了低分子量的聚N-乙烯基甲酰胺。详细研究了单体质量分数、混合溶剂配比、引发剂用量、链转移剂用量、反应温度及反应时间对聚合反应的影响。在最佳聚合条件下,聚合物收率可达93.1%、聚合物的数均分子量(Mn)为2 975.2,PDI=2.64,且聚合残液可循环利用。然后将所得聚合物在酸性条件下水解,制备了不同胺化度的聚N-乙烯基甲酰胺-co-乙烯胺,产品的数均分子量为1 000~1 400,PDI为1.34~1.40。     

Analysis by mass spectrometry of the hydrolysis/condensation reaction of a trialkoxysilane in various dental monomer solutions

3‐Methacryloxypropyltrimethoxysilane (MPTMS) was converted to silsesquioxane oligomers by hydrolysis/condensation in three dental monomer solutions. The molecular mass distribution and molecular structures of these oligomers was studied by matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry. Each dental monomer imparted distinct characteristics on the oligomeric silsesquioxane produced. Ethoxylated bisphenol A dimethacrylate (EBPADMA) produced low‐mass oligomer silsesquioxanes that showed complete hydrolysis and a very high degree of intramolecular condensation (i.e., there were no methoxy and few silanol groups remaining on the oligomers). 1,6‐Bis(methacryloxy‐2‐ethoxycarbonylamino) 2,4,4‐trimethylhexane also produced fully hydrolyzed oligomeric silsesquioxanes but with twice the average molecular mass as the EBPADMA. Finally, triethylene glycol dimethacrylate produced higher mass oligomeric silsesquioxanes than EBPADMA even though it showed incomplete hydrolysis. The degree of hydrolysis increased with increasing mass, as did the degree of intramolecular condensation. Oligomers with degrees of polymerization below 8 were poorly hydrolyzed and showed little if any intramolecular condensation. Those with degrees of polymerization of 9 or greater were almost completely hydrolyzed with a high level of intramolecular condensation. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 1842–1847, 2006     

Alkaline extraction of xylan from wood using microwave and conventional heating

This study aims to investigate the effect of microwave heating versus conventional heating for the alkaline hydrolysis of xylan from birch wood to understand the effect of the heating process on the dissolution of wood, the yield of xylan, and the degree of polymerization of the isolated xylan. The results indicate that the rate of wood dissolution is significantly higher (0.020/s) during microwave extraction than the conventional extraction (0.001/s). Wood solubilization, after an initial rapid removal of damaged fibers, is linear with time for both conventional and microwave extraction, with microwave showing a rate 20 times faster. The yield of xylan reaches a limit of about 60% for both processes but then declines slowly as thermal degradation become significant. Microwave heating provides 60% yield in 1/10th the time of the conventional process. This is found to be associated with the rapid temperature rise, and also with local “hot spots” generated during microwave treatment. The results indicated that xylan degradation was significant above 95°C. The nature of the isolated xylan was different for the two heating methods: the xylan isolated using microwave extraction for 20 min exhibits higher molecular weight (i.e., a greater degree of polymerization, about 150) than the xylan isolated using conventional extraction for the same duration (degree of polymerization, about 124) demonstrating the effectiveness of microwave heating for extraction of xylan from wood. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41330.     

碳酸钠―蒸汽爆破预处理对麦草化学成分及酶水解效率的影响

研究了碳酸钠―蒸汽爆破预处理对麦草化学成分及后续酶水解的影响。结果表明,预处理麦草浆料中木质素含量随预处理中碳酸钠用量的增大而下降,木聚糖和阿拉伯聚糖含量随碳酸钠用量的增大而上升。当碳酸钠用量增加到8%以后,继续增加碳酸钠用量,预处理麦草浆料中的葡聚糖、木聚糖、阿拉伯聚糖和木质素含量基本保持稳定。酶用量较低时,不添加碳酸钠的预处理麦草浆料酶水解葡聚糖得率最大。除不添加碳酸钠的预处理外,酶水解葡聚糖和总糖得率随木质素含量下降而提高。提高酶用量后木质素含量对预处理麦草浆料酶水解葡聚糖得率的影响变缓。     

The heterogeneous character of the dilute acid hydrolysis of crystalline cellulose

The end-attack model proposed by Sharples [Trans. Faraday Soc., 53 , 1003 (1957)] for the dilute acid hydrolysis of crystalline cellulose was tested using the results from the size-exclusion chromatographic analysis of samples of crystalline cellulose I and cellulose II hydrolyzed in 6.1N HCl at 107°C. The differential number distribution of the molecular weight of hydrolyzed cellulose was found to be approximately exponential, a result which is consistent with the end-attack model. Differences in the rates of hydrolysis of cellulosic materials appear to arise from differences in both the degree of polymerization and the microstructure of hydrolyzed cellulose. Evidence is also presented which suggests that the recrystallization upon hydrolysis results in part from the lateral accretion of chains which are cleaved during the hydrolysis of amorphous regions in the cellulose microfibrils.     

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。