Study on the morphology, crystalline structure and thermal properties of yellow ginger starch acetates with different degrees of substitution

Yellow ginger starch acetates with different degrees of substitution (DS) were prepared by reacting native starch with glacial acetic acid/acetic anhydride using sulfuric acid as catalyst. X-ray diffraction (XRD) of acetylated starch revealed that the crystal structure of native starch was disappeared and new crystalline regions were formed. Their formation was confirmed by the presence of the carbonyl signal around 1750 cm⁻¹, as well as the reduced hydroxyl groups, in the Fourier transform infrared spectroscopy (FT-IR). The scanning electron microscopy (SEM) suggested most of the starch granules disintegrated with many visible fragments along with the increasing DS. The thermal behavior of the native starch and starch acetate were investigated using thermogravimetric analysis (TGA) and differential thermal analysis (DTA), it was observed that the thermal stability of acetylated starch depends on the degree of substitution. Thermal stability of high DS acetylated starch is much better than that of the original starch when DS reached to 2.67.     

Acetylation of DMSO:PF solutions of cellulose

Three different techniques for esterifying solutions of cellulose dissolved in mixtures of dimethyl sulfoxide (DMSO) and paraformaldehyde (PF) were evaluated and are herein described. The evaluation and development of suitable synthetic procedures and the characteristics of the resulting acetylated cellulose are reported. Glacial acetic acid (glacial HOAc), acetyl chloride (AcCl), and acetic anhydride (Ac₂O) were compared as acetylating agents for solutions of cellulose in DMSO:PF, and it was demonstrated that mixtures of pyridine (Py) and Ac₂O rapidly acetylated the cellulose to yield beige to amber acetone-soluble cellulose acetates which were partially oxidized. These thermoplastic resins exhibited softening points between 80 and 110°C and thermal stabilities (in nitrogen atmospheres) similar to those of native celluloses (350 to 375°C). Degree of acetyl substitution (DS) values ranged from 0 to 2.0 as a function of acetylation time.     

Preparation of LDPE-acetylated/butyrylated starch blend blow films and characterization

Development of modified plastics has been studied through the LDPE-acylated starch blend films to examine the effect of different acyl groups and degrees of substitution(DS) on properties of films.Corn starch was modified with acetyl and butyryl groups and films were prepared by blending acylated starch with low density polyethylene(LDPE).Systematic studies were done to observe the effect of acyl groups,DS and starch concentration on the properties and biodegradability of the blend films.It was observed that blend films containing 5% acetylated and butyrylated starches of high DS(2.5,1.7) maintained 75% and 83% of tensile strength of LDPE films.Thermal analysis results indicated that acetylated and butyrylated starch blend films decomposed at 370 °C and 389 °C which were higher than the decomposition temperature of native starch film(349 °C).Scanning electron micrographs of blend films containing high DS acylated starch showed well dispersed starch particles due to improvement in dispersion between starch and LDPE.Water absorption capacity of high DS acetylated and butyrylated starch blend films(4.18% and 3.76%,respectively) was lower than that of native starch films(5%).This study has an advantage because of blown films prepared can be integrated with the present manufacturing systems without any other requirement.     

高直链淀粉乙酸酯的均相合成及其静电纺丝

离子液体1-烯丙基-3-甲基咪唑氯盐(amimCl)可以有效地溶解高直链淀粉.以amimCl为均相反应介质,在无外加催化剂的存在下一步合成了取代度范围较宽的高直链淀粉乙酸酯.考察了反应时间和酰化试剂用量对酰化程度的影响.不同取代度的酰化淀粉在水、丙酮和DMAc等溶剂中表现出不同的溶解性.进一步对高直链淀粉乙酸酯溶液进行静电纺丝,制备出了由直径在数十至数百纳米、表面光滑、连续的纳米纤维组成的超细纤维多孔膜.     

Specificity of an Aspergillus Niger Esterase Deacetylating Cellulose Acetate

A purified acetyl esterase (AE), isolated from a commercial enzyme preparation, released acetic acid from water-soluble and water-insoluble cellulose acetates (CAs), native and chemically acetylated xylan as well as acetylated starch. The AE specifically cleaved off the acetyl substituents from the C₂- and C₃-positions from CAs of DS <1.8 and left the acetyl substituents at the C₆-positions intact without degrading the polysaccharide. The activity of endoglucanase was enhanced by the presence of acetyl esterase, while the acetyl esterase derived no advantage from the presence of the endoglucanase; it was able to function independently.     

Novel cellulose derivatives. V. Synthesis and thermal properties of esters with trifluoroethoxy acetic acid

Esters of cellulose with trifluoroethoxy acetic acid (TFAA) were prepared in homogeneous phase using a mixed anhydride with p‐toluenesulfonic acid. Esters with low degree of substitution (DS), and with DS rising from 0 to 3, had hydrophobic character that prevented the usual association with moisture, which is otherwise typical of cellulose esters with low DS. Cellulose trifluoroethoxy acetate (CT) had T_g's declining by about 40 °C per DS‐unit (from 160 to 41 °C) as DS rose from 1 to 3. Mixed esters, cellulose derivatives with acetate and trifluoroethoxy acetate substituents (CAT), exhibited glass‐to‐rubber and melting transitions by DSC. A linear relationship between both T_g and T_m with respect to DS was recorded with the T_g and T_m separated by 30° to 40 °C. This is consistent with cellulose esters described elsewhere. Surprisingly, the T_g's of CT and CAT were found to be identical when the DS was equivalent to the DS of the fluoro substituents (DS_F). © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 486–494, 2000     

Development of an analytical method for yam saponins using HPLC with pulsed amperometric detection at different column temperatures

Yam saponins (dioscin, gracillin, protodioscin, and protogracillin) were analyzed with three different C18 columns at incremental column temperatures from 15 to 45°C to investigate the effect of temperature on the retention and resolution of yam saponins. At low temperature, yam saponins showed decreased retention times and improved resolutions in the C18 columns. In the Kinetex C18 column at 15°C, the four saponins achieved baseline separation (Rs > 1.5) within 30 min. Pulsed amperometric detection was used to identify saponins with high sensitivity. The limits of detection and quantification of saponins were 0.11–0.31 and 0.33–0.95 ng, respectively. The correlation coefficients ranged 0.9986–1.0000. Intra‐ and inter‐day precisions were <4.2% of retention times and <9.5% of the calculated contents. Average recoveries ranged from 92.18 to 105.98%. Saponin contents in Dioscorea nipponica tubers and commercial yam foods were determined without sample purification or concentration. Among the ten commercial yam foods investigated, only three showed significant saponin contents.     

Rheological investigation of starch polysaccharide gelation

Small-amplitude dynamic measurements of aqueous starch polysaccharide solutions are performed by a Bohlin controlled-stress rheometer with air bearing. Three classes of starch polysaccharides–native starches, fractions of starches and hydrolysed starches–are compared in their molecular composition and rheological properties during and after the gelation process. Viscoelastic properties of solutions and gels are recorded in dependence on temperature and time, yielding storage and loss moduli during and after sol-gel transition. Hot concentrated aqueous solutions are cooled down from 90 °C to 5 °C at a rate of 1 °C/min. Measurements are carried out at 0,1 Hz and 5% strain amplitude deformation. The typical course of the moduli of gelling starch polysaccharide solutions shows a liquid-like behavior (G” > G') in the upper temperature level between 60 and 90 °C, a jumpwise increase with ensuing intersection of G' and G” below 60 °C and a solid-like behavior (G' > G”) at lower temperatures with a slightly in time growing storage modulus. Storage and loss moduli depend on molecular composition and concentration of the substance. The process of starch polysaccharide aggregation is discussed with regard to theories of physical gelation by Ross-Murphy and Winter.     

High activity of Mj HSP16.5 under acidic condition

Small heat shock proteins (sHSPs) exist ubiquitously among all organisms, with a variety of functions. All small heat shock proteins assemble into a native large oligomeric state containing 9–40 monomers. The sHSPs show chaperone-like activity to prevent the aggregation of nonnative proteins under stressful cellular conditions such as non-optimal temperatures, pH changes, osmotic pressure, and exposure to toxic chemicals. It was found that a common dimeric subunit of sHSPs might be the major active species, but whether the native large oligomeric state is only a storage state or a state crucial to its molecular chaperone activity is still under debate. The native large oligomeric state of the small heat shock protein from a hyperthermophilic methanarchaeon, Methanococcus jannaschii (Mj HSP 16.5), is a stable icositetramer, which is a symmetric hollow sphere that is very stable even at 85°C, and no small active subunit has been detected till now. Our results show that Mj sHSP 16.5 changes into small and active oligomeric state at pH 3, likely as octamers (average result) at 25°C, and dimers at 65°C. The dimer of Mj HSP 16.5 at pH 3.0 and 65°C is very active and efficient, even 7-fold more efficient than the high-temperature-activated icositetramer at neutral pH. Monomer exchange can be observed between dimers of Mj HSP 16.5 at pH 3.0 and 65°C. These results not only demonstrate that the icositetramer structure of Mj sHSP16.5 is not necessary for its molecular chaperone activity, but also suggest that Mj sHSP16.5 is a very efficient chaperone acting at high temperature and under the acidic condition. Even though it is not clear whether the native environment of Methanococcus jannaschii is acidic or not, given its ability to excrete acidic compounds, it is likely that Methanococcus jannaschii will encounter acidic internal or external environments at high temperature. Our results demonstrate that Mj HSP 16.5 may help Methanococcus jannaschii to survive better under those extreme environmental conditions. Supported by the National Natural Science Foundation of China (Grant Nos. 20203001, 20673003, and 30490245) and Ministry of Science and Technology of China (Grant No. 2006AA02Z301)     

Thermal stability and degradation of starch derivatives

Thermal behaviour of different starch derivatives, i.e. starch esters and ethers having degree of substitution (DS) in the range of 0.02–0.18 were studied. Potato, maize and wheat starches were used. Measurements were carried out by coupled thermal analysis/ mass spectrometry method (STA-MS) in air atmosphere. The major DTG peak during the investigation for starch derivatives is observed below 300°C. The mass loss up to a temperature of 300°C is about 50%. The most abundant ions found areH₂O⁺ and CO₂ ⁺. For the studied starch derivatives with a low degree of substitution (DS<0.18) no correlation was found between thermal stability and the level of substitution regardless of the nature of substitution.     

Cleavage or Acetyl-de-alkylation of 4-Methoxybenzyl (MPM) Ethers Using Acetic Acid

Aryl (4-methoxyphenyl)methyl (MPM) ethers are cleaved by heating with acetic acid for a few hours at 90°C, producing the corresponding phenols and (4-methoxyphenyl)methyl acetate. Under the same conditions alkyl MPM ethers are transformed directly into the corresponding alkyl acetates.     

The Annealing of Acetylated Potato Starch with Various Substitution Degrees

This study aimed to determine the effect of “annealing” acetylated potato starch with a homogenous granule size and various degrees of substitution on the thermal pasting characteristics (DSC), resistance to amylases, rheology of the prepared pastes, swelling power and dynamics of drug release. A fraction of large granules was separated from native starch with the sedimentation method and acetylated with various doses of acetic anhydride (6.5, 13.0 or 26.0 26 cm³/100 g starch). The starch acetates were then annealed at slightly lower temperatures than their pasting temperatures. The annealing process caused an almost twofold increase in the resistance to amylolysis and a threefold increase in the swelling power of the modified starch preparations. The heat of phase transition decreased almost two times and the range of starch pasting temperatures over two times, but the pasting temperature itself increased by ca. 10 °C. The 40 g/100 g addition of the modified starch preparation decreased the rate of drug release from a hydrogel by ca. one-fourth compared to the control sample.     

Diacetylene–siloxane–carborane thermosets and ceramic precursors

Thermosets and ceramic chars were prepared and characterized from a diacetylene–siloxane–carborane polymer, DSCS, and a diacetylene–siloxane polymer, DS. The goal was to incorporate the known thermo‐oxidative stability found in the siloxane–carborane elastomers into high‐performance thermosets and ceramic chars. The DSCS thermoset had excellent thermo‐oxidative stability as determined by a low weight loss and tough residue after annealing for 100 h in air at 300 °C, but it had a low glass transition temperature (94 °C). The DS thermoset did not undergo a glass transition below 350 °C and had a low weight loss on thermo‐oxidative aging, but the residue was quite brittle. Two random copolymers were made to optimize the thermo‐oxidative stability and toughness of the DSCS thermoset and the higher glass transition of the DS thermoset. Significantly, the 50:50 DSCS/DS random copolymer when cured to a thermoset did not undergo a glass transition below 350 °C, yet retained much of the strength, toughness and thermo‐oxidative stability of the DSCS thermoset. Heat treatment of the poly‐DSCS to elevated temperatures resulted in a ceramic material with improved properties relative to the ceramic derived from poly‐DS. Both polymers had similar char yields to 800 °C, but the poly‐DSCS solidified to a 15% denser ceramic. Copyright © 2000 John Wiley & Sons, Ltd.     

Sorption of alkyl acetates from aqueous solutions by corn starch cryotextures

Capillary gas chromatography was used to study noncovalent sorption ofn-butyl,n-hexyl, andn-octyl acetates from aqueous solutions by corn starch cryotextures. In the concentration range of 0.5–15.0 mmol L⁻¹, about 38%n-butyl acetate, 70%n-hexyl acetate, and 98%n-octyl acetate are extracted from aqueous solutions. The sorption of the alkyl acetates depends on the alkyl chain length, indicating the hydrophobic character of their interaction with the corn starch cryotexture. No competitive sorption between acetates in the mixture was observed. Binding of alkyl acetates occurs during the cryosponge formation, due probably to the templation at the stage of starch sol, fixation in the cryosponge, and sorption on the surface of its walls. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1943–1945, October, 1998.     

Dense compounds of C,H, N,and O atoms: II [1]. Nitramine and nitrosamine derivatives of 2-oxo- and 2-iminooctahydroimidazo-[4,5-d]imidazole

The 4,6-dinitroso derivative 11 was obtained (83%) by the nitrosation of 2-oxooctahydroimidazo[4,5-d]-imidazole 1 as the dihydrochloride and was converted to the 4,6-dinitro derivative 12 [66%] by treatment with nitric acid (100%, -40°C) and to the 1,4,6-trinitro derivative 13 (66%) and the 1,3,4,6-tetranitro derivative 2 (86%) by treatment with nitric acid (100%) in acetic anhydride at 0–5°C and 10–25°C respectively. Similar treatment with nitric acid (100%) in either acetic or trifluoroacetic anhydride at 0–25°C converted the trinitro compound 13 to the tetranitro compound 2 (86%). The dinitramine 12 was also obtained (43%) from the diamine 1 by nitration with nitric acid (100%, -40°C). A reaction between 2-nitrimino-5-iminooctahydroimidazo[4,5-d]imidazole 7 as a hydrochloride salt (from an acid catalyzed condensation between 4,5-dihydroxy-2-nitriminoimidazolidine 6 and guanidine) and nitric acid (100%, -40°C) gave the 2,5-dinitrimino derivative 14 (85%) isolated as a monohydrate. The nitrate salt 7 · HNO₃, isomeric with 14 · H₂O, was obtained from the corresponding hydrochloride 7 · HCl and silver nitrate. Both nitrimines 7 and 14 gave 1,3,4,6-tetranitro-2,5-dioxooctahydroimidazo[4,5-d]imidazole 15 (66% and 59%) by treatment with nitric acid (100%) in acetic anhydride.     

Biodegradation of Starch-Based Materials

Abstract

The aim of this study was to compare three different test methods for assaying the biodegradability of starch-based materials. The materials tested included some commercial starch-based materials and thermoplastic starch film prepared by extrusion from native potato starch and glycerol. Enzymatic hydrolysis was performed using excess Bacillus licheniformis α-amylase and Aspergillus niger glucoamylase at 37°C. The degree of degradation was assayed by measuring the dissolved carbohydrates and the weight loss of the samples. The head-space test was based on carbon dioxide evolution using sewage sludge as an inoculum. The composting experiments were carried out in an insulated commercial composter bin. The degradation was evaluated visually at weekly intervals, and the weight loss of the samples was measured after composting. Good correlation was found among the three different test methods.     

Isolation of Cyclodextrin Producing Thermotolerant Paenibacillus sp. from Waste of Starch Factory and Some Properties of the Cyclodextrin Glycosyltransferase

A Cyclodextrin (CDs) producing bacteria was isolated from waste of starch factory in Thailand and identified as Bacillus circulans by biochemical characterization and Paenibacillus sp. by 16S rRNA. The Paenibacillus grew and produced cyclodextrin glycosyltransferase (CGTase) at temperature range 37–45 °C. The optimum culturing conditions for highest CD-forming activity were pH 10.0 and 40 °C for 72 h in Horikoshi broth containing 0.5% soluble starch. The CGTase was partially purified by starch absorption, with 64% recovery and purification fold of 27. The optimum temperatures for dextrinizing and CD-forming activity were 70 and 50–55 °C. At the optimum temperature, the optimum pH for dextrinizing activity was 6.0, while CD-forming activity was 7.0. When the enzyme was incubated for 1 h at different temperatures, CD-forming activity retained its full activity up to 70 °C while dextrinizing activity dropped to 60%. Cyclodextrin products analyzed by HPLC was α:β=1:1, temperature of reaction mixture can affect the yield of CDs.     

Some aspects of acylation of cellulose under homogeneous solution conditions

Commercially available cellulose (Avicell PH101) was successfully acylated under homogeneous solution conditions by the following procedure: 2.0 g of cellulose were stirred with 75 mL of N,N‐dimethylacetamide for 1 h at 150°C, 3.5 g of LiCl were added, the temperature was raised to 170°C, ca. 18.5 mL of the solvent were distilled and the suspension was cooled to room temperature and stirred overnight. The temperature of the clear cellulose solution was raised to 110°C, kept at that temperature for 1 h, an acid anhydride was added and the solution stirred at 110°C for additional 4 h. Acetates, propionates, butyrates, and acetate/propionate mixed ester were prepared with excellent control of the degree of substitution, DS, 1 to 3 for acetates, 2 and 3 for propionates and butyrates, and 3 for acetate/propionate. The degree of polymerization of cellulose is negligibly affected under these reaction conditions. The distribution of the acetyl moiety among the three OH groups of the anhydroglucose unit shows a preference for the C₆ position. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 1357–1363, 1999     

Preparation and pervaporation performance of high-quality silicalite-1 membranes

High-performance silicalite-1 membranes were successfully synthesized on novel porous silica tubes by two-step in-situ hydrothermal synthesis.The flux and separation factor towards ethanol/water mix- ture at 60℃were 0.56 kg/(m2·h)and 84,respectively.The as-synthesized silicalite-1 membranes were characterized by scanning electron microscopy(SEM).The influence of different synthesis conditions on the separation performance of the silicalite-1 membranes was investigated.It was found that the average flux of silicalite-1 membranes was improved by about 26?ter filling the silica tubes with mixed solution containing glycerol and water.After calcinating at 400℃for 5 h repeatedly,membrane synthesized on silica tube still showed high pervaporation performance towards ethanol/water mixture even at a calcination rate of 4℃/min,which suggested that silica support was more suitable for pre- paring high-performance silicalite-1 membranes.     

Growth Inhibition of Thermotolerant Yeast,Kluyveromyces marxianus,in Hydrolysates from Cassava Pulp

In this study, we report the inhibition of Kluyveromyces marxianus TISTR5925 growth and ethanol fermentation in the presence of furan derivatives and weak acids (acetic acid and lactic acid) at high temperatures. Cassava pulp, obtained as the waste from starch processing, was collected from 14 starch factories located in several provinces of Thailand. At a high temperature (42 °C), the cassava pulp hydrolysate from some starch factories strongly inhibited growth and ethanol production of both K. marxianus (strain TISTR5925) and Saccharomyces cerevisiae (strain K3). HPLC detected high levels of lactic acid and acetic acid in the hydrolysates, suggesting that these weak acids impaired the growth of K. marxianus at high temperature. We isolated Trp-requiring mutants that had reduced tolerance to acetic acid compared to the wild-type. This sensitivity to acetic acid was suppressed by supplementation of the medium with tryptophan.