Production of cyclic tetrasaccharide from starch using a novel enzyme system from Bacillus globisporus C11

Production of cyclo[-->6)-alpha-D-Glcp-(1-->3)-alpha-D-Glcp-(1-->6)-alpha-D-Glcp-(1-->3)-alpha-D-Glcp-(1-->] (CTS, cyclic tetrasaccharide) from starch was attempted using 1,6-alpha-glucosyltransferase (6GT) and 1,3-alpha-isomaltosyltransferase (IMT) from Bacillus globisporus C11. The optimal conditions for production from partially hydrolyzed starch were as follows: substrate concentration, 3%; pH 6-7; temperature, 30 degrees C; 6GT, 1 unit/g-dry solid (DS); IMT, 10 units/g-DS. The production of CTS was demonstrated and 544 g of CTS hydrate crystal powders were obtained from 3500 g of partially hydrolyzed starch. Two major by-products were also isolated from the reaction mixture and identified as the branched derivatives of CTSs, 4-O-alpha-D-glucopyranosyl-CTS and 3-O-alpha-isomaltosyl-CTS.     

6-Alpha-glucosyltransferase and 3-alpha-isomaltosyltransferase from Bacillus globisporus N75

A bacterial strain, Bacillus globisporus N75, produced two glycosyltransferases, 6-alpha-glucosyltransferase (6GT) and 3-alpha-isomaltosyltransferase (IMT), jointly catalyzing formation of cyclo-->6)-alpha-D-Glcp-(1-->3)-alpha-D-Glcp-(1-->6)-alpha-D-Glcp-(1-->3)-alpha-D-Glcp-(1--> (CTS) from alpha-1,4-glucan. The N75 enzymes produced CTS from dextrin in a 43.8% yield at the reaction temperature of 50 degrees C, which was 10 degrees C higher than a critical temperature of CTS-forming by the enzymes from B. globisporus C11. The optimum temperatures for 6GT and IMT reactions were 55 degrees C and 50 degrees C, respectively. The thermal stability of both enzymes was 45 degrees C under the condition at pH 6.0 for 60 min. The genes for 6GT and IMT were cloned from the genomic DNA of N75. The amino acid sequences deduced from the 6GT and IMT genes showed 82% and 85% identities, respectively, to the sequences of the enzymes from C11. CTS yield was decreased by high concentrations of the substrate. It was found that the reaction yield was improved by adding cyclomaltodextrin glucanotransferase (CGTase). We demonstrated mass-production of CTS from starch by using the N75 enzymes and CGTase.     

Production and Characterization of Branched Oligosaccharides from Liquefied Starch by the Action of B. Licheniformis Amylase

A branched oligosaccharides (BOS) mixture was produced from liquefied starch solution using a maltogenic amylase of Bacillus licheniformis (BLMA). The BOS mixture was produced by both α-1,4-bond hydrolyzing and α-1,6-transglycosylation activities of BLMA, and it contained 58.3% of various branched oligosaccharides. Small branched oligosaccharides such as isomaltose, isopanose, and panose were identified in the mixture by various analyses including high performance ion-chromatography (HPIC). Major branched DP4 and DP5 molecules in the mixture were determined as 6²-O-α-maltosylmaltose, 6³-O-α-maltosyl-maltotriose and 6²-O-α-maltotriosyl-maltose, respectively. Time course study of BOS production suggested that the hydrolysis and transglycosylation reactions catalyzed by BLMA were coupled. BLMA was likely to transfer a sugar moiety hydrolyzed from a non-reducing end of maltooligosaccharide, mainly maltose, to another moiety of sugar via the formation of α-1,6-linkage. Immobilization of BLMA was attempted as an effort to achieve a continuous process for BOS production. the immobilized enzyme showed improved thermal stability and slight loss of enzyme activity was observed during repeated usage.     

Catalytic Properties of Bacillus megaterium Amylase

A new amylolytic enzyme from Bacillus megaterium is described, which is produced as a trace contaminant in a complex protein mixture, with β-amylase as the major enzyme. By genetic engineering, the productivity could be increased by a factor 10000, and the enzyme is free of other amylases. Compared to pullulanase, which catalyses pullulan degradation to maltotriose, B. megaterium amylase (BMA) does not attack 1,6-linkages and hydrolyses pullulan exclusively to panose. Furthermore, it hydrolyses crosslinked Phadebas starch, used for determination of α-amylases and it also catalyses transfer reactions. Those are strongly enhanced in presence of suitable acceptors, which can be sugar molecules with the same configuration as dextrose in C2, C3, C4-position. In the industrial dextrose process, about 1% of oligosaccharides remains from starch which is difficult to be hydrolysed, thus reducing yield and quality of the final product. The structure elucidation showed 35% 1,6-linkages being present. These oligosaccharides can be degraded and eliminated by BMA through panosyl transfer to dextrose, under formation of 6³-α-glucosylmaltotriose, which is degraded by glucoamylase to dextrose.     

Enzymatic synthesis of l-menthyl alpha-maltoside and l-menthyl alpha-maltooligosides from l-menthyl alpha-glucoside by cyclodextrin glucanotransferase

l-Menthyl alpha-D-glucopyranosyl-(1-->4)-alpha-d-glucopyranoside (alpha-MenG2), a novel glycoside of l-menthol, was synthesized enzymatically and its physicochemical properties were characterized. Production of alpha-MenG2 from l-menthyl alpha-d-glucopyranoside (alpha-MenG) was attempted since we had already succeeded in the high-yield production of alpha-MenG using a Xanthomonas campestris enzyme (Nakagawa H., et al. J. Biosci. Bioeng., 89, 138-144, 2000). Through production tests on enzymes, it was confirmed that cyclodextrin glucanotransferase (CGTase) from Bacillus macerans produced l-menthyl alpha-D-maltooligosides (alpha-MenG(n)), containing alpha-MenG2, from alpha-MenG and soluble starch. When 10 ml of a 10 mM citrate-10 mM phosphate buffer (pH 6.0) containing 150 mg of alpha-MenG, 3 g of soluble starch and CGTase was shaken at 70 degrees C for 24 h, a total of 81.8% alpha-MenG was reacted. The molar conversion yields of alpha-MenG2 and alpha-MenG(n) with alpha-glucose degrees of polymerization of 3-18, based on the amount of alpha-MenG supplied, reached 16.1% and 65.7%, respectively. For efficient production of alpha-MenG2, the reaction mixture was treated with alpha-amylase of Aspergillus oryzae, and alpha-MenG(n) were mainly converted into alpha-MenG2: finally, the molar conversion yield of alpha-MenG2 reached 74.2% based on the amount of alpha-MenG supplied. alpha-MenG2 was purified and its molecular structure was confirmed by 13C-NMR, 1H-NMR and two-dimensional HMBC (heteronuclear multiple-bond coherence). alpha-MenG2 and its aqueous solution tasted bitter and a little sweet at first, but in a few minutes, a refreshing flavor and sweetness spread. At 20 degrees C the solubility of alpha-MenG2 in pure water was 29.6 g/100 ml, approximately 1570-fold that of alpha-MenG.     

Steady and oscillatory shear behaviour of semi-concentrated starch suspensions

The viscoelastic moduli G’ and G” of aqueous suspensions with 40% (w/v) normal corn starch (NCS) and waxy corn starch (WCS) were determined by oscillation rheometry. The oscillatory shear flow experiments at heating from 30° to 75 °C and maintaining at this temperature showed changes from a behaviour predominant viscous (G”>>G’) to predominant elastic (G’>G”) for both starches at 60.5 °C for WCS, respectively 70,85 °C for NCS, WCS having higher values of G’ and G” as NCS. After the gelatinisation temperature was attired, NCS showed no significant changes, both moduli remaining relatively constant. Peaks of both moduli G’ and G” were obtained for WCS at its maintaining at 75^oC, these changes being attributed to the changes in the amylopectin structure in the absence of amylose for this starch type. The frequency influenced the results; analysis at constant low frequency (10 s^-1) gave big oscillations during the measurements and made the analysis impossible, whereas frequencies as 50 s^-1 or 100 s^-1 gaves reproducible and similar results. The shear flow measurements realised at angular frequencies ω from10^-1 to 10³s^-1 at 25^oC showed that changes from a behaviour predominant elastic (G’>G”) to predominant viscous (G”>>G’) occurred when ω attired the values 10 s^-1 for WCS and 3 s^-1 for NCS. The calculation of the ‘Power-Law’ parameter B showed that NCS forms a physical gel structure, whereas WCS behaves as a covalent gel in the frequency domain 10^-1 to 10 s^-1 and as physical gel in the frequency domain 10 to 10² s^-1.     

The Influence of Pullulanase and α-Amylase upon the Oligosaccharide Product Spectra of Wheat Starch Hydrolysates

By hydrolyzing wheat starch solutions using different combinations of ä-amylase and pullulanase it has been possible to achieve significantly different oligosaccharide product spectra in hydrolysates with the same dextrose equivalent (D. E.). Where pullulanase was used either as a pretreatment to α-amolysis or in combination with α-amylase starch hydrolysates were produced whose oligosaccharide product spectra differed significantly from the comparable hydrolysate at the same D.E. produced by α-amylase alone. Throughout the range of starch hydrolysate D.E. values the following trends were observed: pullulanase involvement produced less G1, G2 and G5 oligosaccharides and less intermediate molecular weight fraction (D.P. > 12) than when α-amylase alone was used. Where the D.E. values exceeded 20, in addition to these general differences, pullulanase involvement was found to be responsible for the increased production of G6 and G3 oligosaccharides and to significantly reduce the amount of unhydrolyzed polysaccharide both in the intermediate and high molecular weight fractions.     

Characterization of an Exo-Maltotetraose-forming Amylase of Pseudomonas stutzeri and Application in p-Nitrophenyl β-D-Galactosyl-α-Maltooligosaccharides Production

Some kinetic characteristics and hydrolytic action patterns on various β-D -galactosyl-maltooligosaccharides (Gal-Gn), ranging in size from D.P. (degree of polymerization) 5 to 8, of an exo-maltotetraose-forming amylase of Pseudomonas stutzeri (G4-amylase) were examined to produce a few p-nitrophenyl β-D -galactosyl-α-maltooligosaccharides (Gal-GnP, n = 4,5). The relative hydrolytic reaction rates for larger Gal-Gn by the enzyme were larger than those for smaller saccharides tough the values for unmodified linear maltooligosachharides were almost same. Michaelis constants (Km) for hydrolysis of Gal-G4, Gal-G5, Gal-G6 and Gal-G7 by the enzyme were 1.3, 1.9, 1.3 and 1.3mM, and apparent molecular activities (ko) for these saccharides were 5.9, 38, 91 and 126s⁻¹, respectively. The values of ko/Km for them were remarkably smaller than those for unmodified linear maltooligosaccharides. The G4-amylase cleaved 2 points of the α-1,4-glucosidic linkage in β-1,4-Gal-G4 to give β-1,4-Gal-G2 and -Gal-G3 in the molar ratio of 3:1, whereas the enzyme attacked 3 points of the linkage in β-1,4-Gal-G5, -Gal-G6 and -Gal-G7 to form β-1,4-Gal-G2,-Gal-G3 and Gal-G4 in the molar ratios of 2:5:1, 1:3:6 and 1:3:6, in the early stage of the reaction, respectively. On the other hand, the enzyme showed no action on β-1,6-Gal-G4 and formed β-1,6-Gal-G4 solely from β-1,6-Gal-G5, and β-1,6-Gal-G4 and -Gal-G5 were from β-1,6-Gal-G6 and -Gal-G7 in the ratios of 8:1 and 2:1, respectively. The enzyme also catalyzed the transfer action to produce Gal-G3P, Gal-G4P and Gal-G5P, of which the formation ratio was coincided well with the hydrolytic action pattern on each Gal-Gn, from Gal-Gn tested as a donor and p-nitrophenyl α-glucoside (GP) as an acceptor in an aqueous solution containing 40% (v/v) methanol. By using this novel reaction, Gal-G5P is now producing on an industrial scale to apply as a substrate for the assay of human α-amylase.     

Ethanol Production From Raw Sago Starch Under Unsterile Condition

In order to utilize raw sago starch as fermentation material, mold strain (Aspergillus niger N-10) which produces raw sago starch hydrolyzing enzyme, was isolated. Maximum raw sago starch consumption rate by the strain was obtained when the initial pH of the medium was 3.5 and the enzyme showed high stability and activity at lower pH values. Direct ethanol production from raw sago starch was investigated using a mixture of the strain and ethanol producing yeast, Saccharomyces cerevisiae IFO 0309. Neither the growth of the strains nor ethanol production was inhibited in the mixed culture of the two strains. Moreover, when fed-batch mixed culture was conducted under unsterile condition (both the medium and the apparatus were not sterilized), about 30g/1 of ethanol was produced with ethanol yield from raw sago starch Y_p/s of 0.40g ethanol/g starch.     

Characterization of Enzyme Released Antioxidant Phenolic Acids and Xylooligosaccharides from Different Graminaceae or Poaceae Members

Xylooligosacchrides (XOS) and phenolic acids were simultaneously produced from hemicelluloses using crude enzyme mixture synthesized by a novel Bacillus subtilis KCX006. The strain synthesized XOS-forming endo-xylanase and de-branching α-L-arabinofuranosidase and esterase but not β-xylosidase. This enzyme mixture can improve the yield of XOS and phenolic acids from xylan due to the absence of hydrolysis of XOS by β-xylosidase and release of phenolic acids by esterase. Hence, the enzyme mixture was tested for simultaneous production of XOS and phenolic acids from xylan (28–35%)-rich Graminaceae or Poaceae plant biomass, such as wheat bran, sugarcane bagasse, bamboo, and rise husk. Hemicellulose fractions of the biomasses were extracted by alkaline treatment and hydrolyzed using crude xylanase mixture. The profiles of XOS and phenolic acids formed were analyzed by HPLC. The lyophilized hydrolytic products were further analysed by ¹H NMR to identify the substitutions in XOS. The observed profile of XOS and phenolic acids varied with the biomass sources. Maximum amounts of XOS (665.2 mg/g dwt) and phenolic acids (89.69 μg/g dwt) were produced from hemicellulose A fractions of sugarcane bagasse and bamboo bagasse, respectively. HPLC and ¹H NMR analysis of XOS revealed the formation of free- and arabino-XOS. Phenolic acids consisted of hydroxycinnamic and hydroxybenzoic acids and the antioxidant activity correlated well with hydroxycinnamic acids content. The crude enzyme of B. subtilis is useful to produce mixture of XOS and phenolic acids from biomass.     

Acceptor recognition of kojibiose phosphorylase from Thermoanaerobacter brockii: syntheses of glycosyl glycerol and myo-inositol

The glucosyl transfer reaction of kojibiose phosphorylase (KP; EC 2.4.1.230) was examined using glycerol or myo-inositol as an acceptor. In the case of glycerol, KP produced two main transfer products: saccharides A and B. The structure of saccharide A was O-alpha-D-glucopyranosyl-(1-->1)-glycerol and that of saccharide B was O-alpha-D-glucopyranosyl-(1-->2)-O-alpha-D-glucopyranosyl-(1-->1)-glycerol. These results show that KP transferred a glucose residue to the hydroxyl group at position 1 of glycerol. On the other hand, when myo-inositol was used as an acceptor, KP produced four transfer products: saccharides 1-4. The structures of saccharides 1 and 2 were O-alpha-D-glucopyranosyl-(1-->1)- and O-alpha-D-glucopyranosyl-(1-->5)-myo-inositol, respectively; those of saccharides 3 and 4 were O-alpha-D-glucopyranosyl-(1-->2)-O-alpha-D-glucopyranosyl-(1-->1)- and O-alpha-D-glucopyranosyl-(1-->2)-O-alpha-D-glucopyranosyl-(1-->5)-myo-inositol, respectively. KP transferred a glucose residue to the hydroxyl group at position 1 or 5 of myo-inositol. On the basis of the structures of their glucosyl transfer products, glycerol and myo-inositol were found to have a common structure with three hydroxyl groups corresponding to the hydroxyl group of the glucose molecule at positions 2, 3 and 4. The conformation of these three hydroxyl groups in the structure is equatorial. This structure is the substrate recognition site of KP. It has been suggested that KP strictly recognizes the structures of glycerol and myo-inositol, and catalyzes the transfer reaction of a glucose residue to the hydroxyl group at position 1 in glycerol, and at position 1 or 5 in myo-inositol, corresponding to position 2 in glucose.     

Inhibition of cholesterol biosynthesis and acetyl-coenzyme A synthetase by bovine milk and orotic acid.

Pasteurized, homogenized bovine milk or orotic acid in solution at final concentrations varying from 3.3 μM to 322 μM in rat liver homogenates inhibited the incorporation of [1-Carbon 14] acetate but not [1-Carbon 14] acetyl-coenzyme A, 3-hydroxy-3-methyj-[Carbon 14] glutaryl-coenzyme A or [5-hydrogen 3] mevalonic acid into cholesterol. Milk inhibited cholesterol biosynthesis up to 72 ± 10% before acetyl-coenzyme A formation, thus indicating that acetyl-coenzyme A synthetase is the affected enzyme. Kinetics of the inhibition were studied with acetyl-coenzyme A synthetase purified from yeast. From a Line-weaver-Burk plot of the inhibition of yeast acetyl-coenzyme A synthetase, orotic acid is a noncompetitive inhibitor of acetyl-coenzyme A synthetase. A Michaelis constant was 6.0 × 10^?4 M for acetate with the yeast enzyme while a K_i was 6.6 × 10^?5 M for orotic acid. The approximate point of 50% inhibition with rat liver enzyme was 7 × 10^?6 M orotic acid indicating the mammalian enzyme may be more sensitive to the orotic acid. Nicotinic acid also inhibited the yeast enzyme. Fifty percent inhibition required a relatively high final concentration–about 12 mM. Neither raw milk nor pasteurized, homogenized milk inhibited 3-hydroxy-3-methyl-glutaryl-coenzyme A reductase that had been partially purified from rat liver.     

Continuous Production of Glucose Syrup in an Ultrafiltration Reactor

An ultrafiltration reactor was developed for the continuous saccharification of liquefied corn starch using glucoamylase. At an enzyme concentration of 1 g/L and a substrate concentration of 300 g/L, maltose and maltotriose were still detected in the reactor permeate after 4 hr of operation. At higher enzyme concentrations (6 and 12 g/L), the reactor achieved steady-state operation within 1–3 hr at all substrate concentrations studied. At an enzyme concentration of 12 g/L, residence time did not affect the final conversion of liquefied starch to glucose. The ultrafiltration reactor produced glucose syrups at residence times of 2–3 hr and substrate concentrations up to 30% w/v.     

Enzymatic synthesis of novel oligosaccharides from L-sorbose, maltose, and sucrose using kojibiose phosphorylase

Glucosyl-L-sorbose, -maltose, and -sucrose were synthesized using kojibiose phosphorylase (KPase) from Thermoanaerobacter brockii ATCC35047 with beta-D-glucose-1-phosphate (beta-G1P) as a glucosyl donor. One disaccharide and two trisaccharides thus synthesized were isolated by Toyopearl HW-40S column chromatography. The results of KPase digestion, methylation analysis, and 13C-NMR studies indicated that these oligosaccharides were alpha-D-glucopyranosyl-(1-->5)-alpha-L-sorbopyranose, alpha-D-glucopyranosyl-(1-->2)-alpha-D-glucopyranosyl-(1-->4)-D-glucopyranose (4-alpha-D-kojibiosyl-glucose), and alpha-D-glucopyranosyl-(1-->2)-alpha-D-glucopyranosyl-(1-->2)-beta-D-fructofuranoside, which are all novel oligosaccharides. Glucosyl-L-sorbose was partially hydrolyzed to glucose and L-sorbose by alpha-glucosidases, while glucosyl-sucrose and glucosyl-maltose were not hydrolyzed by glucoamylase, alpha-glucosidases, or CGTase.     

烟草中淀粉降解菌的筛选、鉴定及发酵工艺优化

从河南初烤烟叶表面分离筛选得到一株淀粉降解菌HX-6,并对菌株产酶培养基和烟叶发酵工艺进行优化.结果表明:淀粉降解菌HX-6为枯草芽孢杆菌(Ba-cillus subtilis),其最佳产酶培养基配方为:可溶性淀粉与红薯淀粉(m可溶性淀粉:m红薯淀粉=1:1)17.0 g/L,蛋白胨与酵母粉(m蛋白胨:m酵母粉=1:1...     

无矾红薯粉丝的研制及加工工艺

将合成的红薯淀粉磷酸酯与魔芋粉及复合磷酸盐复配,以不同比例加入红薯淀粉中,在不同的条件下生产无矾粉丝。结果表明:当红薯淀粉磷酸酯的加入量为6%;m(魔芋粉)∶m(复合磷酸盐)=2∶3,加入量为1%;搅拌机匀浆,在冷冻条件开粉;干燥温度45℃、干燥时间为3h时生产出的粉丝在断条率和烹煮损失率方面都优于加矾粉丝。     

Synthesis of glycosyl glycerol by cyclodextrin glucanotransferases

Glycerol was transglycosylated by cyclodextrin glucanotransferases using starch as a donor substrate. Among the enzymes tested, those from Geobacillus stearothermophilus and Thermoanaerobacter sp. were suitable for the transglycosylation. Several products were isolated and their structures were elucidated. They were composed of glucose and a series of a-1,4-linked maltooligosyl residues bound with glycerol. O-alpha-D-Glucosyl-(1-->1)-glycerol and O-alpha-D-glucosyl-(1-->2)-glycerol were identified as the major and minor components of the smallest transfer products, respectively. O-alpha-D-Glucosyl-(1-->4)-O-alpha-D-glucosyl-(1-->1)-glycerol was also identified as a main dimer product. Reducing sugars were produced in extremely low amounts. The optimum temperatures for the transglycosylation by G. stearothermophilus and Thermoanaerobacter enzymes were approximately 60 degrees C and 80 degrees C, respectively. The reaction of 30% (w/v) glycerol and 20% (w/v) soluble starch was optimum for efficient transglycosylation. Maltosyl and maltotriosyl glycerols inhibited porcine pancreas a-amylase significantly, whereas the monomer, glucosyl glycerol, exhibited much weaker inhibition.     

Effects of sourdough and enzymes on staling of high-fibre wheat bread

The effects of sourdough and enzyme mixture (α-amylase, xylanase and lipase) on the specific volume, staling and microstructure of wheat pan bread supplemented with wheat bran were studied. Staling of bread was followed for 6 days by measuring the crumb firmness, changes in crystallization of amylopectin (DSC), increase in signal from the solid phase (NMR) and by light microscopy. The most effective treatment in improvement of quality was the combination of bran sourdough and enzyme mixture. During storage the rate of changes in crumb firmness, amylopectin crystallinity and rigidity of polymers were greatest for the white wheat bread. The most pronounced microstructural changes were swelling of starch granules and separation of amylose and amylopectin in the starch granules. Least changes in crumb firmness, amylopectin crystallinity and rigidity of polymers were observed in bran sourdough bread with enzymes. In contrast to white wheat bread, the starch granules were very much swollen in bran sourdough bread with enzyme mixture. This was hypothesized to be due to the higher water content of bran bread, and degradation of cell wall components leading to altered distribution of water among starch, gluten and bran particles during storage.     

Gel texture and chain structure of amylomaltase-modified starches compared to gelatin

Amylomaltase (AM) (4-α-d-glucanotransferase; E.C. 2.4.1.25) from Thermus thermophilus was used to modify starches from various botanical sources including potato, high amylose potato (HAP), maize, waxy maize, wheat and pea, as well as a chemical oxidized potato starch (Gelamyl 120). Amylopectin chain length distribution, textural properties of gels and molecular weight of 51 enzyme and 7 non-enzyme-modified starches (parent samples) were analyzed. Textural data were compared with the textural properties of gelatin gels. Modifying starch with AM caused broadening of the amylopectin chain length distribution, creating a unimodal distribution. The increase in longer chains was supposedly a combined effect of amylose to amylopectin chain transfer and transfer of cluster units within the amylopectin molecules.Exploratory principal component analysis (PCA) data analysis revealed that the data were composed of two components explaining 94.2% of the total variation. Parent starches formed a cluster separated from that of the AM-modified starches.Extended AM treatments reduced the apparent molecular weight and the gel texture without changing the amylopectin chain length distribution. However, the gel texture was typically increased as compared to the parent starch. AM-modified HAP gels were about twice as hard as gelatin gels at identical concentration, whereas gels of pea starch were comparable to gelatin gels. Modifying Gelamyl 120 and waxy maize with AM did not change the textural properties. Branching enzyme (BE) (1,4-α-d-glucan branching enzyme; EC 2.4.1.18) from Rhodothermus obamensis was used in just one modification and in combination with AM. The combined AM/BE modification of pea starch resulted in starches with shorter amylopectin chains and pastes unable to form gel network even at concentration as high as 12.0% (w/w). The PCA model of all gel texture data gave suggestive evidence for starch structural features being important for generating a gelatin-like texture.     

水-离子液体混合溶液对玉米淀粉溶解的影响

研究新型离子液体(ionic liquid,IL)-1-烯丙基-3-乙烯基咪唑醋酸盐对普通玉米淀粉溶解性能的影响。采用偏光显微镜(polarized light microscopy,PLM)、X-射线衍射仪(X-ray diffraction,XRD)、差示扫描量热仪(differential scanning calorimetry,DSC)、扫描电子显微镜(scanning electron microscope,SEM)等淀粉表征手段,揭示水和离子液体混合溶液对玉米淀粉溶解的影响。结果发现,通过偏光显微镜和扫描电子显微镜可以观察到在水和离子液体的摩尔比为4∶1时玉米淀粉的颗粒的“马耳他”十字消失,颗粒结构明显变形,从X-射线衍射结果可以看出水和离子液体比为4∶1(摩尔比)处理的玉米淀粉X-射线的衍射峰的峰强度明显减弱,且淀粉的典型A型晶体的特征峰消失,表明淀粉晶体结构遭到严重破坏。通过DSC的结果可以看出,静置60 min后,水∶离子液体为4∶1(摩尔比)处理的淀粉DSC峰没有吸热峰或者放热峰出现,说明相对于其他的比例而言,水和离子液体的比例为4∶1(摩尔比)对淀粉的溶解效果最好。