Silylation of Cellulose and Starch – Selectivity, Structure Analysis, and Subsequent Reactions

The silylation of cellulose and starch under different starting conditions is reviewed. The control of the degree of substitution (DS) and regioselectivity in dependence of the reaction pathway are discussed in detail. The synthesis of trimethylsilyl cellulose (TMSC) in the system hexamethyldisilazane (HMDS)/ammonia leads to partially and completely silylated products controlled by the amount of the components. Hydrolytic desilylation of TMSC in tetrahydrofuran (THF)/ammonia gives the partially desilylated products. The desilylation proceeds statistically along the polymer chains. The reaction of cellulose dissolved in N,N-dimethylacetamide (DMA)/LiCl with bulky thexyldimethylchlorosilane (TDSCl) in the presence of imidazole leads to 2,6-di-O-TDS cellulose. The silylation of starch dissolved in dimethylsulfoxide (DMSO) with TDSCl/pyridine results in the formation of regioselectively 2-O and 6-O functionalized silyl ethers with DS values up to 1.8. 6-O Silyl ethers of cellulose and starch were synthesized with TDSCl highly activated in the reaction system N-methylpyrrolidone (NMP)/ammonia. Two- dimensional NMR techniques after subsequent modifications of the remaining OH groups have been established as important methods for the characterization of the substitution pattern of the described silyl ethers. In the case of starch, the distribution of the substituents could be detected not only in the anhydroglucose units (AGU) but also in the non-reducing end groups (NEG).     

A new potentiometric sensor for the determination of α-amylase activity

A platinum redox sensor for the direct potentiometric determination of α-amylase concentration has been described. The sensor measured the amount of triiodide released from a starch-triiodide complex, which was correlated with the α-amylase activity after biocatalytic starch degradation. The composition and stability of the potassium triiodide solution was optimized. The starch-triiodide complex was characterized potentiometrically at variable starch and triiodide concentrations. The response mechanism of the platinum redox sensor towards α-amylase was proposed and the appropriate theoretical model was elaborated. The results obtained using the redox sensor exhibited satisfactory accuracy and precision and good agreement with a standard spectrophotometric method and high-sensitive fully automated descret analyser method. The sensor was tested on pure α-amylase (EC 3.2.1.1, Fluka, Switzerland), industrial granulated α-amylase Duramyl 120 T and an industrial cogranulate of protease and α-amylase Everlase/Duramyl 8.0 T/60 T. The detection limit was found to be 1.944 mU for α-amylase in the range of 0-0.54 U (0-15 μg), 0.030 mKNU for Duramyl 120 T in the range of 0-9.6 mKNU (0-80 μg) and 0.032 mKNU for Everlase/Duramyl 8.0 T/60 T in the range of 0-9.24 mKNU (0-140 μg).     

毛细管电泳法快速测定淀粉中可乐定

提出了毛细管电泳快速测定淀粉中可乐定含量的方法。以pH 2.2的磷酸-25 mmol.L-1磷酸二氢钠缓冲溶液为电解质溶液,分离电压20 kV,于214 nm波长处进行紫外检测。在优化的试验条件下,可乐定的质量浓度在0.3~200 mg.L-1范围内与其对应的校正峰面积呈线性关系。检出限(3S/N)为0.1 mg.L-1,测定下限(10S/N)为0.3 mg.L-1。采用该方法对淀粉样品中可乐定含量进行测定,所得加标回收率在97.1%~98.4%之间,相对标准偏差(n=5)小于2.0%。     

Critical review on alterations in physiochemical properties and molecular structure of natural polysaccharides upon ultrasonication

Natural polymers, such as polysaccharides, cellulose, and starch, have been widely used in the chemical engineering, medicine, food, and cosmetics industries, which had a great many of biological activities. Natural polysaccharides origin from algae, fungi and plants were components of human diet since antique times. Ultrasonication achieved the breakage the polysaccharides reticulum in an ordered fashion. The factors of temperature, ratio of water/material, sonication frequency, time of exposure, pH of the sonication medium influenced the polysaccharide digestion. Sonication improved the enzyme catalysis over its substrate molecule. Positive health promoting slow digestive starch and resistant starch can be prepared quite easily by the sonication process. The aim of this review is to present the current status and scope of natural polymers as well as some emerging polymers with special characteristic. The physiochemical properties and molecular structure of natural carbohydrates under ultrasonic irradiation were also discussed. Moreover, Polysaccharide based films had industrial applications is formed by ultrasonication. Polysaccharide nanoparticles obtained by sonication had efficient water holding capacity. Sonication is an advanced method to improve the food quality. Hence, this review describes the effects of ultrasonication on physical, chemical, and molecular structure of natural polysaccharides.     

大黄种子中蛋白质、多糖和淀粉含量的测定

采用凯氏定氮法、苯酚-硫酸比色法和双波长比色法测定唐古特大黄种子、掌叶大黄种子和药用大黄种子的蛋白质、多糖和淀粉的含量.采用凯氏定氮法测定蛋白质含量,苯酚-硫酸比色法测定多糖含量,双波长比色法测定淀粉含量.唐古特大黄种子的蛋白质和多糖在三种大黄种子中含量最高,分别为21.81％、6.58％,掌叶大黄种子淀粉含量在三种大黄种子中最高,含量为32.95％.三种大黄种子中,蛋白质含量为：唐古特大黄种子＞掌叶大黄种子＞药用大黄种子;多糖含量为：唐古特大黄种子＞掌叶大黄种子＞药用大黄种子;淀粉含量为：掌叶大黄种子＞唐古特大黄种子＞药用大黄种子.大黄种子的蛋白质、多糖、淀粉含量丰富.测定方法精密度、准确度、稳定性均符合生物样品测定要求,可用于大黄种子蛋白质、多糖和淀粉含量的测定.     

Aliphatic polyester-grafted starch composites by in situ ring opening polymerization

Catalyzed Ring-Opening Polymerization (ROP) of lactones, such as ε-caprolactone and δ-valerolactone, has been investigated for preparing aliphatic polyester-grafted corn starch compositions. The polymerization has been carried out either in bulk (without solvent) or in 10 wt% granular starch in toluene suspension, after adequate activation of the starch surface amylose/amylopectin hydroxyl groups into aluminum alkoxides. This activation has been done by in situ reaction with triethylaluminum and has proved to be very effective in promoting fast ROP and also covalent grafting of the polyester chains onto the starch surface. Drying of the starch granules constitutes a key-step of the proposed process. The actual fixation of the initiator onto the starch surface has been checked by XPS analysis whereas good adhesion between the two components has been evidenced by SEM observations. Growth of the polyester chains on the starch granules has been followed by the increase of the mean diameter of the 'encapsulated' granules as attested by laser scattering granulometry.     

Low frequency ultrasonic-assisted hydrolysis of starch in the presence of α-amylase

Hydrolysis of starch is an important process in the food industry and in the production of bioethanol or smaller carbohydrate molecules that can be used as starting blocks for chemical synthesis. Such hydrolysis can be enhanced by lowering the pH, heating the reaction mixture or catalyzing the reaction with enzymes. This study reports the effect of sonication on the reaction rate of starch hydrolysis at different temperatures, in the presence or absence of alpha-amylase. Starch Azure, a commercially available potato starch covalently linked with Remazol Brilliant Blue, has been chosen since its hydrolysis releases a blue dye, which concentration can be monitored by UV Vis spectroscopy. Ultrasounds, regardless of experimental conditions, provide the highest reaction rate for such hydrolysis.     

The ex-situ and in-situ ultrasonic assisted oxidation of corn starch: A comparative study

The objective of this study was to evaluate the differences in ex-situ (starch treated by ultrasonication and oxidation sequentially, U-OS) and in-situ (starch treated by ultrasonication and oxidation simultaneously, UOS) ultrasonic assisted oxidation process of corn starch, which were studied in contrast to the traditional oxidized starches (OS). Fourier-transform infrared spectra confirmed the successful oxidation of all modified starches samples. In comparison to the OS, the carboxyl contents of U-OS and UOS increased by 56% and 112%, respectively. The same increase trend was also found for the carbonyl contents. The significance raise was attributed to the great increase of pores and specific surface areas in the starch granule after ultrasonic irradiation which promoted the penetration of the sodium hypochlorite into the starch granules with higher chances for chemical reactions. SEM and pore size distribution characterizations further verified this result. However, the method of in-situ ultrasonic assisted oxidation can simultaneously accelerate the increase of pores and the penetration process. Consequently, the starches with higher oxidation degree can be more efficiently prepared by the strategy of in-situ ultrasonic assisted oxidation.     

不同产地山药的XRF和PXRD分析与表征

共用X射线荧光(XRF)和X射线衍射(PXRD)技术从整体上对河北道地药材——祁山药和市售山药的元素种类、含量及主要组分的微结构进行测定并对比分析。结果表明,祁山药比市售山药多Mg,Zn,Cr元素,少Cu,Al,Mn元素,且两组山药的元素含量也有所不同;两组山药中均含有淀粉,但市售山药为C+V型淀粉结构,祁山药为B型结构,同时都含少量的一水草酸钙。这两种技术共用适于对山药的元素和微结构分析及产地的表征与鉴别。     

原子力显微镜在多糖结构研究中的进展

简述了原子力显微镜(AFM)的工作原理和特点,以及在多糖,特别是在淀粉结构研究中的进展。