Salt-assisted acid hydrolysis of chitosan to oligomers under microwave irradiation

The effect of inorganic salts such as sodium chloride on the hydrolysis of chitosan in a microwave field was investigated. While it is known that microwave heating is a convenient way to obtain a wide range of products of different molecular weights only by changing the reaction time and/or the radiation power, the addition of some inorganic salts was shown to effectively accelerate the degradation of chitosan under microwave irradiation. The molecular weight of the degraded chitosan obtained by microwave irradiation was considerably lower than that obtained by traditional heating. Moreover, the molecular weight of degraded chitosan obtained by microwave irradiation assisted under the conditions of added salt was considerably lower than that obtained by microwave irradiation without added salt. Furthermore, the effect of ionic strength of the added salts was not linked with the change of molecular weight. FTIR spectral analyses demonstrated that a significantly shorter time was required to obtain a satisfactory molecular weight by the microwave irradiation-assisted inorganic salt method than by microwave irradiation without inorganic salts and conventional technology. (C) 2005 Elsevier Ltd. All rights reserved.

Salt-assisted acid hydrolysis of starch to D-glucose under microwave irradiation

The effect of inorganic salts on the hydrolysis of starch in a microwave field was investigated and it was found that some inorganic salts can effectively accelerate the acid hydrolysis of starch. The yield of D-glucose reached 111 wt% (equal to the theoretical yield). (C) 2001 Published by Elsevier Science Ltd. All rights reserved.

一株丝状真菌对半纤维素利用的初步研究

本文筛选出一株能利用木糖产乙醇的丝状真菌Z7，对其利用木糖和半纤维素水解产物产乙醇的发酵条件进行了研究，并对Z7 利用玉米芯产木聚糖酶的条件进行了优化。全文分为三部分： 第一部分：目标微生物筛选、纯化及系统发育分析。以木糖为唯一碳源，采用梯度稀释和平板化线法从高温、中温酒曲中分离到16 株能利用木糖良好生长的丝状真菌；通过发酵试验复筛，获得一株能产乙醇的丝状真菌Z7；综合形态学和ITS 序列分析，初步鉴定为Aspergillus flavus。 第二部分：Z7 的乙醇发酵条件研究。以木糖为碳源，通过单因素试验确定最佳氮源和发酵温度；通过正交试验及SPSS 软件分析得到了不同N、P、K 成分对乙醇、残糖和菌体干重的影响。获得最佳的发酵条件为：（g/L）木糖50，尿素1, NH4NO3 1, K2HPO4 2 , KCl 0.5 , MgSO4.7H2O 0.5 , NaNO3 1 , pH 自然，培养温度33 ℃。以玉米芯半纤维素稀酸水解液为底物进行乙醇发酵，根据稀酸水解的单糖释放量和乙醇产量，确定115 ℃，1 h 为最佳玉米芯预处理条件；结合最佳发酵条件，添加1 g/L 的吐温20 能获得最大的乙醇浓度8.31 g/L。因此，Aspergillus flavus Z7 能利用半纤维素水解产物产乙醇，其中木糖的利用率80%以上。 第三部分：Z7 利用玉米芯产木聚糖酶条件优化。Aspergillus flavus Z7 在具有产乙醇能力的同时还具有产木聚糖酶的能力。本文通过单因素和正交试验得到最佳产酶培养基组分为：(g/L)玉米芯20，尿素2, 酵母膏2.5, K2HPO4 5，NaNO31, MgSO4.7H2O 1。单因素试验表明，用纱布代替塑料布密封摇瓶封口能显著提高产酶量；Z7 在碱性条件下具有更强的产酶性能。在最优条件下发酵，能产生最大木聚糖酶活122.23IU/mL。通过薄层分析，验证了Z7 产生的木聚糖酶具有水解木聚糖生成木糖及木寡糖的能力。 A strain of filamentous fungus which can produce ethanol by using the xylose was isolated in this research. The ethanol fermention conditions from xylose and dilute-acid hydrolyzate of the corn core were studied. The conditions of xylanase production by Z7 were also optimized. The paper involved three parts. Part1: Isolation, purification and phylogenetic analysis of the microbe. By using xylose as the single carbon source and the pla te streaking method, several filamentous fungi were isolated from the wine starter; through the fermentation test, a filamentous fungus Z7 which can produce ethanol was further recognized; furthermore, according to the morphologic observation and ITS seque nces analysis, Z7 was identified as Aspergillus flavus at the first step. Part2: Research on the condition of ethanol fermentation by Z7. By single factor experiment, the optional nitrogen resource and temperature of the fermentation were fixed; meanwhile, through the orthogonal array tests and the analysis of statistic software SPSS, the optional component of the culture medium and the fermentation condition were organized as follows: (g/L) xylose 50, urea 1, NH4NO3 1, K2HPO4 2, KCl 0.5 , MgSO4.7H2O 0.5, NaNO31, pH nature, temperature 33℃. Based on these optimal parameters, the fermentation of dilute-acid hydrolyzate of the corn core was carried on by Z7. According to the quantities of released sugar monomers and content of the ethanol, 115℃ in 1h is the best pretreatment condition; the maximal ethanol content can be obtained when 1g/L Tween 20 was added to. Therefore, the filamentous fungus Aspergillus flavus can use the hydrolysate of hemicellulose to produce ethanol, and the rate of xylose utilization was over 80%. Part3: Optimization of Z7’s xylanase producing condition from corn core. Aspergillus flavus Z7, which can utilize xylose or the hydrolysate of hemicellulose to produce ethanol, also had the ability of xylanase production. The optional component of the culture medium were fixed by the single factor experiment and the orthogonal array tests, and they were organized as follows: (g/L) corn core 20, Urea 2, Yeast extract 2.5, K2HPO4 5, NaNO31, MgSO4.7H2O 1; it was testified by the single factor experiment that sealing the shaking flasks with pledget other than plastic paper can obviously increase the xylanase activity; moreover, Z7 showed better xylanase production ability when in the alkali environment. Under the optional fermentation condition, the maximal xylanase activity 122.23IU/mL was proved. Through the analysis of thin- layer chromatography (TLC), the ability of xylanase from Z7, which can hydrolyze xylan to xylose monomer and oligomer, was vividly displayed.

羟基自由基降解琼胶及其产物的活性研究

琼胶是一种从石花菜等红藻中提取的，目前生产工艺和结构等方面研究比较成熟的海藻多糖，广泛应用于医药、仪器等行业。但是，海藻多糖因为具有分子量大，粘度大，溶解度较小的等特点，而使其应用范围受到限制。利用降解的手段对其进行修饰，降低分子量和粘度，改善溶解性，可以拓展其应用范围。并且根据文献报道，琼 胶寡糖具有一些特殊的生物活性，如抗氧化性，抗炎症等。因此，对琼胶降解的研究具有生要意义。本研究中，为了选择一种合适的降解方法，进行了几种水解方法的尝试，其中包括在不同湿度和酸度下盐酸水解，过氧化氢和醋酸催化水解，Fenton体系羟基自由基降解。对于酸水解和Fenton体系氧化还原降解方法，通过粘度法对反应的速度进行了比较，表明氧化还原降解反应中琼胶的粘度降低比较快，并且具有代表性和新意，确定为本实验的降解琼胶的方法并对氧化还原降解所得的产物进行了活性实验。通过模仿自然界普遍存在的氧化还原降解反应，利用Vc诱导的Fenton体系产生的羟基自由基氧化还原降解琼胶得到低分子量的琼胶。降解产物经过高速离心、60％乙醇沉淀，除去分子量比较大的降解产物和磷酸盐，得到可溶于60％乙醇的分子量估计小于3000的降争产物，其产率为85％。利用经Sephadex-G25凝胶色谱分离所香的不同分子量的级分进行分子量和α－葡萄糖苷酶抑制活性关系的实验。降解产物对α－葡萄糖苷酶的抑制率和各级分的浓度呈线性正相关，并且各级分的IC_(50)则随着分子量的降低而降低。另外，对所得的降解产物混合物进行了红外吸收光谱、质子去偶核磁共震碳谱和负离子基质辅助激光诱导－飞行时间质谱结构分析。结果表明，氧化还原降解反应的专一性差，在得到寡糖的同时，在光谱图中出现一些比较复杂的副产物的结构信息。最后，根据MTT法的原理，以有体皮肤成纤维细胞为材料，通过紫外线辐射产生自由基造成氧化损伤，研究降解产物对成纤维细胞的保护作用。当无紫外线辐射时，降解产物对成纤维细胞具有显著的促进生长增殖作用：当经UVa、UBb辐射时则可以显著地表现出对损伤的保护作用，并且这种促进生长和保护作用呈显著的量效关系，表明降解产物具有清除基自由基的作用。但是，因为氧化还原降解以应的机理尚不十分明的以及琼羟胶的特殊结构，使得反应的副产物很难预测，也就使得分离工作难以进行，所以，根据目前所得的信息，尚不能确定是降解产物的什么级分产生的以上两种生物活性。

Studies of polysaccharides from three edible species of Nostoc (cyanobacteria) with different colony morphologies: Structural characterization and effect on the complement system of polysaccharides from Nostoc commune

The cyanobacterium Nostoc commune Vaucher produces quite complex extracellular polysaccharides. The cyanobacterium is nitrogen fixing, and on growing the cyanobacterium in media with and without nitrogen, different types of extracellular polysaccharides were obtained. These were also different from the polysaccharides present in N. commune collected in the field. High pH anion exchange chromatography (HPAEC) of weak acid hydrolysates of the culture-grown material demonstrated that, in this case, HPAEC was useful for comparison of the different polymers. The main differences between the polymers from the field group and the culture-grown samples were the presence of substantial amounts of arabinose, 2-O-methylglucose, and glucuronic acid in the latter. Methylation studies also revealed a difference in the branching points on the glucose units between the field and cultured samples, being 1,4,6 for the first and 1,3,6 for the latter. The field acidic fraction gave, on weak acid hydrolysis and separation on BioGel P2 and HPAEC, 12 oligosaccharide fractions that were isolated and studied by different mass spectroscopy techniques. The structures of the oligosaccharides were determined, and two different series that can originate from two repeating pentamers were identified: GlcAl-4/6GlcM1-4Ga11-4Glc1-4Xyl and GlcAl-4/6Glc1-4Ga11-4Glc1-4Xyl. The difference between these oligosaccharides lies in the methyl substituent on carbon 2 of the glucose unit next to the nonreducing glucuronic acid unit. The polysaccharides from field material were shown to have a strong effect on the complement system.

两种银莲花属植物的化学成分研究

本学位论文由5 章组成。第1 章报道了两头尖中三萜皂苷类化合物的全扫描电喷雾多级质谱分析及银莲花素A 的电喷雾质谱裂解规律；第2 和3 章报道了两种银莲花属药用植物化学成分的研究结果；第4 章报道了银莲花素A 的化学结构修饰及其对一种蛋白酪氨酸磷酸酯酶（PTP-1B）的抑制活性；第5 章综述了电喷雾质谱在皂苷类化合物结构鉴定中的应用进展。 第1 章报道了运用全扫描电喷雾多级质谱对两头尖中三萜皂苷类化合物的快速定性检测，共检测出18 个准分子离子峰，根据多级质谱数据并结合文献报道，对其中的15 个准分子离子峰进行了归属，并区分了一些同分异构体；更有意思的是，发现了3 个未见文献报道的三萜皂苷类化合物。根据它们的多级质谱数据，对其结构分别进行了初步解析。本章同时对银莲花素A 特殊的质谱裂解途径通过衍生物制备及其质谱分析进行了确认。 第2 和3 章，分别报道了两头尖和打破碗花花中水溶性多糖苷的分离纯化和结构鉴定。采用D101 大孔树脂和反复硅胶柱层析等分离手段，从两头尖水溶性部分分离得到8 个三萜皂苷类化合物，通过红外、电喷雾质谱和核磁共振等现代谱学方法，并结合传统的化学手段鉴定了它们的结构，其中4 个化合物为新化合物，分别命名为多被银莲花皂苷19、多被银莲花皂苷20、多被银莲花皂苷21和多被银莲花皂苷22。从打破碗花花水溶性部位分离得到6 个三萜皂苷类化合物，通过现代谱学手段，并结合传统的化学方法对它们进行了鉴定，其中1 个为新化合物，命名为打破碗花花苷H。 第4 章报道了以银莲花素A 及其同系物为先导化合物，进行化学结构修饰并对修饰产物进行广泛的生物活性筛选，发现在银莲花素A 及其同系物的结构中引入一些酸性基团后，其生物活性发生了变化，一些修饰产物显示出很强的PTP-1B 抑制作用，提示这些化合物有可能用于治疗II 型糖尿病。 第5 章综述了电喷雾多级质谱用于皂苷类化合物结构鉴定的研究进展。 This dissertation composes of five chapters. The first chapter elaborates the detection and qualification of the triterpenoidal saponins in Anemone raddeana by positive and negative full scan ESI-MSn. This part also reports the special fragmentation pathway of Raddeanin A by ESI-MS/MS. The second and third chapters present the phytochemical investigation of two medicinal plants from Anemone. The fourth part dwells on the structure modification of Raddeanin A and their inhibitory activity against PTP-1B. The last part is a review on the progress in the application of ESI-MSn in the structure identification of saponins. The first chapter reports the application of full scan ESI-MSn for fast analysis of triterpenoid saponins in Anemone raddeana. Eighteen quasi- molecular ion peaks were detected in the positive full scan ESI-MS and fifteen of them were identified by analysis of their tandem mass spectral data in the negative ion mode. Several isomers were differentiated. More interesting, three unreported triterpenoid saponins in this medicinal plant were detected and their structures were deduced according to the dissociation pathway of the known triterpenoidal saponins. This chapter also confirms the special fragmentation pathway of Raddeanin A by its derivative and the mass spectral analysis. The second and third chapters expatiate on the isolation and identification of the chemical constituents from A. raddeana and A. hupehensis. Eight compounds were isolated from the roots and stems of A. raddeana by methanol extraction and repeated column chromatography (including D101 and silica gel), and their structures were determined on the basis of IR, ESI-MS, NMR and chemical methods (including acid hydrolysis and alkaline saponification). Among them, four are new triterpenoid saponins and named as Raddeanoside R19, Raddeanoside R20, Raddeanoside R21 and Raddeanoside R22. Six compounds were isolated from the whole plants of A. hupehensis by the same methods as above, and their structures were also determined with the same way. One of them was confirmed to be new triterpenoid saponins and named as hupehensis saponin H. In the fourth chapter, in order to look for new active compounds, the structure of Raddeanin A and its analogs were modified. It was found that the modified products exhibited obvious inhibitory activity against PTP-1B when several acid groups were introduced. The fifth chapter summarizes the progress on the application of ESI-MSn in the structure identification of saponins.

Preparation and in vitro antioxidant activity of kappa-carrageenan oligosaccharides and their oversulfated, acetylated, and phosphorylated derivatives

In order to study the relationship between chemical structure and properties of modified carrageenans versus antioxidant activity in vitro, K-carrageenan oligosaccharides were prepared through mild hydrochloric acid hydrolysis of the polysaccharide, and these were used as starting materials for the partial synthesis of their oversulfated, acetylated, and phosphorylated derivatives. The structure and substitution pattern of the oligosaccharides and their derivatives were Studied using FTIR and C-13 NMR spectroscopy, and their in vitro antioxidant activities were investigated. Certain derivatives of the carrageenan oligosaccharides exhibited higher antioxidant activity than the polysaccharides and oligosaccharides in certain antioxidant systems. The oversulfated and acetylated derivatives, which scavenge superoxide radicals, the phosphorylated and low-DS acetylated derivatives, which scavenge hydroxyl radicals, and the phosphorylated derivatives, which scavenge DPPH radicals, all exhibited significant antioxidant activities it, the systems examined. The effect of the molecular weight of the carrageenan on antioxidant activities, however, is not obvious from these studies. (c) 2005 Elsevier Ltd. All rights reserved.

Preparation, structural characterization and in vitro antitumor activity of kappa-carrageenan oligosaccharide fraction from Kappaphycus striatum

Oligosaccharides were prepared through mild hydrochloric acid hydrolysis of kappa-carrageenan from Kappaphycus striatum to compare the antitumor activity with carrageenan polysaccharides. Oligosaccharide fractions were isolated by gel permeation chromatography and the structure of fraction 1 (F1) was studied by using negative- ion electrospray ionization-mass spectrometry (ESI-MS), and H-1 and C-13-NMR spectrometry. The in vitro antitumor effects in three human neoplastic cell lines (KB, BGC, and Hela) of polysaccharides and F1 were investigated. The bioassay results showed that F1 exhibited relatively higher antitumor activity against the three cancer cells than polysaccharides.

Preparation of titania-based catalysts for formaldehyde photocatalytic oxidation from TiCl4 by the sol-gel method

Titania sols were prepared by acid hydrolysis of a TiCl4 precursor instead of titanium alkoxides. The effect of acid concentration on the particle size and stability of sol was investigated. Stable titania sols with mean particle size of 14 nm could be obtained when the H+/Ti molar ratio was 0.5. The titania sols were modified with Pt, SiO2, ZrO2, WO3 and MoO3 to prepare a series of modified catalysts, which were used for the photocatalytic oxidation of formaldehyde at 37 degreesC. They showed different photocatalytic activities due to the influence of the additives. Comparing with pure TiO2, the addition of silica or zirconia increased the photocatalytic activity, while the addition of Pt and MoO3 decreased the activity, and the addition Of WO3 had little effect on the activity. It is of great significance that the conversion of formaldehyde was increased up to 94% over the SiO2-TiO2 catalyst. The increased activity was partly due to higher surface area and porosity or smaller crystallite size. A comparison of our catalyst compositions with the literature in this field suggested that the difference in activity due to the addition of a second metal oxide maybe caused by the surface chemistry of the catalysts, particularly the acidity. (C) 2001 Elsevier Science B.V. All rights reserved.

SOLVENT AND SUBSTITUENT EFFECTS ON THE INTRAMOLECULAR AMIDE HYDROLYSIS OF N-METHYLMALEAMIC ACID

Intramolecular amide hydrolysis of N-methylmaleamic acid is revisited at the B3LYP/6-311G(2df,p)//B3LYP/6-31G(d,p)+ZVPE level, including solvent effects at the CPCM-B3LYP/6-311G(2df,p)//Onsager-B3LYP/6-31G(d,p)+ZPVE level. The concerted reaction mechanism is energetically favorable over stepwise reaction mechanisms in both the gas phase and solution. The calculated reaction barriers are significantly lower in solution than in the gas phase. In addition, it is concluded that the substituents of the four N-methylmaleamic acid derivatives considered herein have a significant effect on the gas-phase reaction barriers but a smaller, or little, effect on the barriers in solution.

Intramolecular amide hydrolysis in N-methylmaleamic acid revisited

The intramolecular amide hydrolysis of N-methylmaleamic acid have been revisited by use of density functional theory and inclusion of solvent effects. The results indicate that concerted reaction mechanism is favored over stepwise reaction mechanism. This is in agreement with the previous theoretical study. Sovlent effects have significant influence on the reaction barrier.

On the acid-base stability of Keggin Al-13 and Al-30 polymers in polyaluminum coagulants

The acid-base stabilities of Al-13 and Al-30 in polyaluminum coagulants during aging and after dosing into water were studied systematically using batch and flow-through acid-base titration experiments. The acid decomposition rates of both Al-13 and Al-30 increase rapidly with the decrease in solution pH. The acid decompositions of Al-13 and Al-30 with respect to H+ concentration are composed of two parallel first-order and second-order reactions, and the reaction orders are 1.169 and 1.005, respectively. The acid decomposition rates of Al-13 and Al-30 increase slightly when the temperature increases from 20 to ca. 35 A degrees C, but decrease when the temperature increases further. Al-30 is more stable than Al-13 in acidic solution, and the stability difference increases as the pH decreases. Al-30 is more possible to become the dominant species in polyaluminum coagulants than Al-13. The acid catalyzed decomposition and followed by recrystallization to form bayerite is one of the main processes that are responsible for the decrease of Al-13 and Al-30 in polyaluminum coagulants during storage. The deprotonation and polymerization of Al-13 and Al-30 depend on solution pH. The hydrolysis products are positively charged, and consist mainly of repeated Al-13 and Al-30 units rather than amorphous Al(OH)(3) precipitates. Al-30 is less stable than Al-13 upon alkaline hydrolysis. Al-13 is stable at pH < 5.9, while Al-30 lose one proton at the pH 4.6-5.75. Al-13 and Al-30 lose respective 5 and 10 protons and form [Al-13] (n) and [Al-30] (n) clusters within the pH region of 5.9-6.25 and 5.75-6.65, respectively. This indicates that Al-30 is easier to aggregate than Al-13 at the acidic side, but [Al-13] (n) is much easier to convert to Alsol-gel than [Al-30] (n) . Al-30 possesses better characteristics than Al-13 when used as coagulant because the hydrolysis products of Al-30 possess higher charges than that of Al-13, and [Al-30] (n) clusters exist within a wider pH range.

Direct synthesis of Al-SBA-15 mesoporous materials via hydrolysis-controlled approach

Aluminum-substituted mesoporous SBA-15 (Al-SBA-15) materials were directly synthesized by a hydrolysis-controlled approach in which the hydrolysis of the silicon precursor (tetraethyl orthosilicate, TEOS) is accelerated by fluoride or by using tetramethyl orthosilicate (TMOS) as silicon precursor rather than TEOS. These materials were characterized by powder X-ray diffraction (XRD), N-2 sorption isotherms, TEM, Al-27 MAS NMR, IR spectra of pyridine adsorption, and NH3-TPD. It is found that the matched hydrolysis and condensation rates of silicon and aluminum precursors are important factors to achieve highly ordered mesoporous materials. Al-27 MAS NMR spectra of Al-SBA-15 show that all aluminum species were incorporated into the silica framework for the samples prepared with the addition of fluoride. A two-step approach (sol-gel reaction at low pH followed by crystallization at high pH) was also employed for the synthesis of Al-SBA-15. Studies show that the two-step approach could efficiently avoid the leaching of aluminum from the framework of the material. The calcined Al-SBA-15 materials show highly ordered hexagonal mesostructure and have both Bronsted and Lewis acid sites with medium acidity.