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1.
Tapioca starch was modified using branching enzyme (BE) isolated from Bacillus subtilis 168 and Bacillus stearothermophilus maltogenic amylase (BSMA), and their molecular fine structure and susceptibility to amylolytic enzymes were investigated. By BE treatment, the molecular weight decreased from 3.1 × 108 to 1.7 × 106, the number of shorter branch chains (DP 6–12) increased, the number of longer branch chains (DP >25) decreased, and amylose content decreased from 18.9% to 0.75%. This indicated that α–1,4 linkages of amylose and amylopectin were cleaved, and moiety of glycosyl residues were transferred to another amylose and amylopectin to produce branched glucan and BE-treated tapioca starch by forming α–1,6 branch linkages. The product was further modified with BSMA to produce highly-branched tapioca starch with 9.7% of extra branch points. When subject to digestion with human pancreatic α-amylase (HPA), porcine pancreatic α-amylase (PPA) and glucoamylase, highly-branched tapioca starch gave significantly lowered α-amylase susceptibility (7.5 times, 14.4 times and 3.9 times, respectively), compared to native tapioca starch.  相似文献   

2.
Diacetyl, a highly valuable product that is extensively used as an ingredient of food, tobacco, and daily chemicals such as perfumes, can be produced from the nonenzymatic oxidative decarboxylation of α-acetolactate during bacterial fermentation and converted to acetoin and 2,3-butanediol by 2,3-butanediol dehydrogenase. In the present study, Bacillus sp. DL01, which gives high acetoin production, was metabolically engineered to improve diacetyl production. After the deletion of α-acetolactate decarboxylase (ALDC)-encoding gene (alsD) by homologous recombination, the engineered strain, named Bacillus sp. DL01-ΔalsD, lost ALDC activity and produced 1.53 g/L diacetyl without acetoin and 2,3-butanediol accumulation. The channeling of carbon flux into diacetyl biosynthetic pathway was amplified by an overexpressed α-acetolactate synthase (ALS)-encoding gene (alsS) in Bacillus sp. DL01-ΔalsD-alsS, which produced 4.02 g/L α-acetolactate and 1.94 g/L diacetyl, and the conversion from α-acetolactate to diacetyl was increased by 1-fold after 20 mM Fe3+ was added to the fermentation medium. A titer of 8.69 g/L diacetyl, the highest reported diacetyl production, was achieved by fed-batch fermentation in optimal conditions using the metabolically engineered strain of Bacillus sp. DL01-ΔalsD-alsS. These results are of great importance as a new method for the efficient production of diacetyl by food-safe bacteria.  相似文献   

3.
In this study raw starch digesting amylase (RSDA) from Aspergillus carbonarius (Bainier) Thom IMI 366159 was stabilized by covalent binding on polyglutaraldehyde (PG), glutaraldehyde (G) activated chitosan beads or post immobilization cross linking of enzyme adsorbed on chitosan. Presence of Ca2+ ions (0.5–1.5 mM) activated the PG and G derivatives but repressed the crosslinked enzyme. Optimum pH for cross linked derivative increased by 2 units but was unaltered for PG and G derivatives. Immobilized amylase exhibited improved thermal and storage stability. Immobilized derivatives had no loss of activity after 1 month storage and retained above 90% activity after 10 batch reactions of 60 min each. Immobilization successfully stabilized RSDA and immobilized enzyme from A. carbonarius can be applied in numerous industries for cheap, cost effective and environmentally friendly starch hydrolytic processes to simple sugars.  相似文献   

4.
In this study, N, N-dimethylacetamide (DMAc) with certain concentration ranges of lithium chloride (LiCl) was used to plasticize starch by melting extrusion. Solid state ionic conductors, DMAc-plasticized starch containing LiCl also had a potential application as solid biopolymer electrolytes. Scanning electron microscope (SEM) showed that many remanent starch granules embed in DMAc-plasticized starch matrix. With increasing LiCl content, the number of remanent starch granules decreased dramatically and homogeneous thermoplastic starch (TPS) could be achieved. Moreover, Fourier Transform infrared (FT-IR) spectroscopy revealed that LiCl could increase the interaction between starch and plasticizers. In addition, the supermolecular structure of starch was destructed by LiCl detected by wide-angle X-ray scattering (WAXS) and thermogravimetric analysis (TGA) respectively. Finally, LiCl not only could increase the water absorption of TPS, but also improved the conductance of TPS. The conductance of TPS with 18 wt% LiCl content could achieve to 10?0.5 S cm?1 at 18 wt% water content.  相似文献   

5.
A thermophilic Bacillus sp. strain AN-7, isolated from a soil in India, produced an extracellular pullulanase upon growth on starch–peptone medium. The enzyme was purified to homogeneity by ammonium sulfate precipitation, anion exchange and gel filtration chromatography. The optimum temperature and pH for activity was 90 °C and 6.0. With half-life time longer than one day at 80 °C the enzyme proves to be thermostable in the pH range 4.5–7.0. The pullulanase from Bacillus strain lost activity rapidly when incubated at temperature higher than 105 °C or at pH lower than 4.5. Pullulanase was completely inhibited by the Hg2+ ions. Ca2+, dithiothreitol, and Mn2+ stimulated the pullulanase activity. Kinetic experiments at 80 °C and pH 6.0 gave Vmax and Km values of 154 U mg−1 and 1.3 mg ml−1. The products of pullulan were maltotriose and maltose. This proved that the purified pullulanase (pullulan-6-glucanohydrolase, EC 3.2.1.41) from Bacillus sp. AN-7 is classified under pullulanase type I. To our knowledge, this Bacillus pullulanase is the most highly thermostable type I pullulanase known to date.  相似文献   

6.
7.
A total of 23 phosphate solubilizing bacteria (PSB) and 35 phosphate solubilizing fungi (PSF) were isolated from 19 samples of salt affected soils. The ability of 12 selected PSB and PSF to grow and solubilize tricalcium phosphate in the presence of different concentrations of NaCl was examined. Among 12 PSB, Aerococcus sp. strain PSBCRG1-1 recorded the highest (12.15) log viable cell count at 0.4 M NaCl concentration after 7 days after incubation (DAI) and the lowest log cell count (1.39) was recorded by Pseudomonas aeruginosa strain PSBI3-1 at 2.0 M NaCl concentration after 24 h of incubation. Highest mycelial dry weight irrespective of NaCl concentrations was recorded by the Aspergillus terreus strain PSFCRG2-1 (0.567 g). The percent Pi release, in general, was found to increase with increase in NaCl concentration up to 0.8 M for bacterial solubilization and declined thereafter. At 15 DAI, strain Aerococcus sp. strain PSBCRG1-1 irrespective of NaCl concentrations showed the maximum P-solubilization (12.12%) which was significantly superior over all other isolates. The amount of Pi released in general among PSF was found to decrease with increase in NaCl concentration at all the incubation periods. Aspergillus sp. strain PSFNRH-2 (20.81%) recorded the maximum Pi release irrespective of the NaCl concentrations and was significantly superior over all other PSF at 7 DAI.  相似文献   

8.
Genetic engineering of Halomonas spp. was seldom reported due to the difficulty of genetic manipulation and lack of molecular biology tools. Halomonas TD01 can grow in a continuous and unsterile process without other microbial contaminations. It can be therefore exploited for economic production of chemicals. Here, Halomonas TD01 was metabolically engineered using the gene knockout procedure based on markerless gene replacement stimulated by double-strand breaks in the chromosome. When gene encoding 2-methylcitrate synthase in Halomonas TD01 was deleted, the conversion efficiency of propionic acid to 3-hydroxyvalerate (3HV) monomer fraction in random PHBV copolymers of 3-hydroxybutyrate (3HB) and 3HV was increased from around 10% to almost 100%, as a result, cells were grown to accumulate 70% PHBV in dry weight (CDW) consisting of 12 mol% 3HV from 0.5 g/L propionic acid in glucose mineral medium. Furthermore, successful deletions on three PHA depolymerases eliminate the possible influence of PHA depolymerases on PHA degradation in the complicated industrial fermentation process even though significant enhanced PHA content was not observed. In two 500 L pilot-scale fermentor studies lasting 70 h, the above engineered Halomonas TD01 grew to 112 g/L CDW containing 70 wt% P3HB, and to 80 g/L CDW with 70 wt% P(3HB-co-8 mol% 3HV) in the presence of propionic acid. The cells grown in shake flasks even accumulated close to 92% PHB in CDW with a significant increase of glucose to PHB conversion efficiency from around 30% to 42% after 48 h cultivation when pyridine nucleotide transhydrogenase was overexpressed. Halomonas TD01 was also engineered for producing a PHA regulatory protein PhaR which is a robust biosurfactant.  相似文献   

9.
The lipase from Bacillus subtillus (BSL2), a highly active lipase expressed from newly constructed strain of Bacillus subtilis BSL2, is used in the kinetic resolution of glycidyl butyrate. A high enantiomeric ratio (E = 108) was obtained by using 1,4-dioxane as co-solvent (18%, v/v) and decreasing the reaction temperature to 5 °C. The ratio is about 16-fold more than that (E = 6.52) obtained in pure buffer solutions (25 °C, pH 7.8). Under the optimum conditions, the remained (R)-glycidyl butyrate with high enantiopure (ee > 98%) was obtained when the conversion was above 52%.  相似文献   

10.
α-Amylase, a very critical enzyme for hydrolysis of starch into simple sugar and it has various applications in industrial settings. This study reports the identification of Bacillus sp. MB6 which produces increased amount of enzyme from less required resources. To optimize the yield of enzyme, we used various combinations of parameters. The most optimized conditions for production of amylase enzyme from the bacterium Bacillus sp. MB6 are pH of 6, temperature of 37 °C, and incubation period of 48 h. Condition of enzymatic activity were also examined and the results show that pH of 6, a temperature of 55 °C, and a reaction time of 30 min are the best available conditions for its activity. Purification of enzyme by 1.63 fold enhanced the specific activity of enzyme based upon its activity analysis as compared with unpurified enzyme. Enzyme kinetics studies show the Michaelis constant (Km) to be 5.45 mg/ml and maximum velocity of the reaction (Vmax) to be 24.15 mg/ml/min. In conclusion, we report enzyme production and purification methodology that exhibit better yield of alpha-amylase for commercial applications.  相似文献   

11.
A bionanocomposite was cast using ZnO nanoparticles stabilized by soluble starch (nano-ZnO) as filler in a glycerol plasticized-pea starch (GPS) matrix. According to the characterization of nano-ZnO particles by Fourier-transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TG) and transmission electron microscopy (TEM), ZnO nanoparitlces (70 wt%) were encapsulated by starch (30 wt%) in nano-ZnO particles of about 10 nm. In GPS/nano-ZnO nanocomposites, loading a low level of nano-ZnO particles improved the pasting viscosity, storage modulus, glass transition temperature and UV absorbance. When the nano-ZnO content varied from 0 to 4 wt%, the tensile yield strength and Young’s modulus increased from 3.94 to 10.80 MPa and from 49.80 to 137.00 MPa, respectively. The water vapor permeability decreased from 4.76 × 10?10 to 2.18 × 10?10 g m?1 s?1 Pa?1. The improvement in these properties may be attributed to the interaction between the nano-ZnO filler and GPS matrix.  相似文献   

12.
The effect of water content on the glass transition temperatures of cassava starch was determined by differential scanning calorimetry (DSC) and dynamic mechanical thermal analysis (DMTA). Samples were transformed to the amorphous state by compression molding at high temperature (as demonstrated by wide angle X-ray diffraction, WAXS), and then the samples were moisture conditioned. Both DSC and DMTA showed that water anti-plasticized cassava starch at lower moisture contents, and plasticized it at higher water contents. Samples with higher moisture contents stored at room temperature, 45 °C and 80 °C underwent retrogradation as indicated by WAXS. Sorption isotherms of cassava starch showed that for aw values lower than around 0.85, the sorption capacity decreased with increasing temperature; while the opposite behavior was observed at aw > 0.85. This inversion point (aw = 0.85) was attributed to the fact that more active sites were exposed to the adsorption processes, due to the enhanced molecular mobility promoted in the amorphous regions by starch crystallization.  相似文献   

13.
The decolorization potential of two bacterial consortia developed from a textile wastewater treatment plant showed that among the two mixed bacterial culture SKB-II was the most efficient in decolorizing individual as well as mixture of dyes. At 1.3 g L?1 starch supplementation in the basal medium by the end of 120 h decolorization of 80–96% of four out of the six individual azo dyes Congo red, Bordeaux, Ranocid Fast Blue and Blue BCC (10 mg L?1) was noted. The culture exhibited good potential ability in decolorizing 50–60% of all the dyes (Congo red, Bordeaux, Ranocid Fast Blue and Blue BCC) when present as a mixture at 10 mg L?1. The consortium SKB-II consisted of five different bacterial types identified by 16S rDNA sequence alignment as Bacillus vallismortis, Bacillus pumilus, Bacillus cereus, Bacillus subtilis and Bacillus megaterium which were further tested to decolorize dyes. The efficient ability of this developed consortium SKB-II to decolorize individual dyes and textile effluent using packed bed reactors is being carried out.  相似文献   

14.
Ionic liquids (ILs), 1-allyl-3-methylimidazolium chloride ([amim]Cl) is found to be a novel plasticizer for cornstarch. [Amim]Cl-plasticized starch film also has a potential application as solid biopolymer electrolytes. In this study, different proportional [amim]Cl/glycerol mixtures are used to plasticize starch by casting. Atomic force microscopy (AFM) finds the diameter of residual starch granules existed in [amim]Cl or glycerol-plasticized starch films is only about 10 nm. However, glycerol can form more intensive hydrogen bond with starch than [amim]Cl detected by Fourier transform infrared (FT-IR) spectroscopy. So some novel ILs with high concentration and active hydrogen bond acceptors are necessary. Moreover, high [amim]Cl content can improve the water absorption and conductance of TPS film simultaneously. The conductance of TPS film with 30 wt% [amim]Cl content can achieve to 10?1.6 S cm?1 at 14.5 wt% water content.  相似文献   

15.
Feruloyl esterases (Faes) are a subclass of the carboxylic esterases that hydrolyze the ester bonds between ferulic acid and polysaccharides in plant cell walls. Until now, the biochemical characteristics of FAEs from Bacillus spp. have not been reported. In this study, a strain with high activity of FAEs, Bacillus amyloliquefaciens H47 was screened from 122 Bacillus – type strains. Finally, three FAEs (BaFae04, BaFae06, and BaFae09) were identified. Comparing with other bacterial FAEs, these novel FAEs exhibited low sequence identities (less than 30%). The profiles of 52 esterase substrates showed that the three FAEs had a broad substrate spectrum and could effectively hydrolyze several common FAE substrates, such as methyl ferulate, ethyl caffeate, methyl p-coumarate, methyl sinapate, and chlorogenic acid. Furthermore, the three FAEs also can release ferulic acid from destarched wheat bran. They showed maximal activity with an optimal pH of 8.0 at 30 °C, 35 °C, and 40 °C, respectively. BaFae04 showed high stability in the temperature range of 25–60 °C for 1 h and retained 59% of its activity at 60 °C. The present study displays some useful characteristics of FAEs for potential industrial application and contributes to our understanding of FAEs.  相似文献   

16.
Rheological comparisons have been made between preparations of high methoxy pectin (DE  70%) gelled by acidification with d-glucono-δ-lactone (GDL) on holding for 16 h at 25 °C in the presence of 60 wt% sucrose, and otherwise identical preparations gelled by acidification with citric acid at high temperature and cooling from 90 to 25 °C at 1 °C/min. Two series of experiments were carried out for both methods of acidification. In the first series, the concentration of pectin (c) was held constant at 1.0 wt% and the final pH attained after holding (with GDL) or cooling (with citric acid) was varied from 3.75 to 2.25. In the second series, the final pH was held constant at 3.0 and c was varied from 0.25 to 2.00 wt%. All samples were then heated (1 °C/min) from 25 to 90 °C. Rheological changes on cooling/holding and heating were characterised by low-amplitude oscillatory measurements of storage modulus (G′) and loss modulus (G′′) at 1 rad s?1 and 0.5% strain, and mechanical spectra were recorded at 25 °C. Selected samples, gelled with GDL, were also characterised by compression testing (at 25 °C), and a direct linear relationship was found between the logarithm of yield stress and log G′.The concentration-dependence of moduli for the samples acidified to pH 3.0 with GDL had the form typical of biopolymer gels, with log G′ versus log c approaching a limiting slope of 2 as c was raised above the minimum critical gelling concentration (co  0.3 wt%). Under all conditions of pH and pectin concentration studied, the values of G′′ (at 25 °C) for the samples acidified with citric acid were higher than those of the corresponding GDL-induced networks. The values of G′ were also higher, except at very low pH (below ~2.7 at c = 1.0 wt%) or very high concentrations of pectin. At pectin concentrations above ~1.5 wt%, the moduli of the samples gelled with citric acid (at pH 3.0) levelled out, or decreased slightly, with the values of G′ dropping below those of the GDL-induced networks towards the end of the concentration range studied (at c  2 wt%). All samples acidified with citric acid showed gel-like response (G > G′′) at 90 °C, attributed to hydrophobic association. The downturn in moduli at 25 °C for high concentrations of pectin is attributed to formation and disruption of strong networks during mixing with citric acid at high temperature (“pregelation”). It is suggested, however, that “weak gels” formed at lower concentrations or at pH values above ~2.7 may enhance gel properties by preserving a continuous network as hydrophobic junctions dissociate on cooling and are replaced by hydrogen-bonded junctions, in contrast to random percolation during gelation with GDL at 25 °C. On re-heating from 25 to 90 °C, the reverse processes (dissociation of hydrogen-bonded structures and formation of hydrophobic associations) were evident in an initial reduction and subsequent increase in moduli, as observed in previous studies. Similar heating traces were obtained for samples acidified with GDL to pH values above ~3.0 (at c = 1.0 wt%) or with pectin concentrations below ~1.0 wt% (at pH 3.0). However, at higher concentrations or lower values of pH (i.e. conditions favourable to extensive intermolecular association) an abrupt decrease in G′, with an accompanying maximum in G′′, was observed on heating through the temperature range ~60–80 °C. This is attributed to excessive hydrophobic association, causing collapse of network structure. It is further suggested that, for samples acidified with citric acid, there is preferential association of chain sequences of high ester content into hydrophobic junctions at 90 °C, leaving sequences with a high content of unesterified carboxyl groups available to form long hydrogen-bonded junctions during cooling, and thus giving gels that are stronger and more resistant to network collapse.  相似文献   

17.
《Process Biochemistry》2010,45(2):230-238
The effectiveness of bioremediation technology in the removal of carbofuran from contaminated soil using a bioslurry phase sequencing batch reactor (SBR) was investigated. A 2-L laboratory glass bottle was used as a bioreactor with a working volume of 1.5 L at room temperature (27 ± 2 °C). One total cycle period of the SBR was comprised of 1 h of fill phase, 82 h of react phase, and 1 h of decant phase. The carbofuran concentration in the soil was 20 mg/kg soil. A carbofuran degrader isolated from carbofuran phytoremediated soil, namely Burkholderia cepacia PCL3 (PCL3) immobilized on corncob, was used as the inoculum. The results revealed that bioaugmentation treatment (addition of PCL3) gave the highest percentage of carbofuran removal (96.97%), followed by bioaugmentation together with biostimulation (addition of molasses) treatment (88.23%), suggesting that bioremediation was an effective technology for removing carbofuran in contaminated soil. Abiotic experiments, i.e. autoclaved soil slurry with corncob and no PCL3 treatment and autoclaved soil slurry with no PCL3 treatment, could adsorb 31.86% and 7.70% of carbofuran, respectively, which implied that soil and corncob could act as sorbents for the removal of carbofuran.  相似文献   

18.
The effect of posterior cruciate ligament (PCL) on muscle co-activation (MCO) is not known though MCO has been extensively studied. The purpose of the study was to investigate the effect of PCL creep on MCO and on joint moment around the knee. Twelve males and twelve females volunteered for this study. PCL creep was estimated via tibial posterior displacement which was elicited by a 20 kg dumbbell hanged on horizontal shank near patella for 10 min. Electromyography activity from both rectus femoris and biceps femoris as well as muscle strength on the right thigh was recorded synchronically during knee isokinetic flexion–extension performance in speed of 60 deg/s as well as 120 deg/s on a dynamometer before and after PCL creep. A one-way ANOVA with repeated measures was used to evaluate the effect of creep, gender and speed. The results showed that significant tibial posterior displacement was found (p = 0.01) in both male and female groups. No significant increase of joint moment was found in flexion as well as in extension phase in both female and male groups. There was a significant effect of speed (p = 0.036) on joint moment in extension phase. Co-activation index (CI) decreased significantly (p = 0.049) in extension phase with a significant effect of gender (p  0.001). It was concluded that creep developed in PCL due to static posterior load on the proximal tibia could significantly elicit the increase of the activation of agonist muscles but with no compensation from the antagonist in flexion as well as in extension phase. The creep significantly elicited the decrease of the antagonist–agonist CI in extension phase. MCO in females was reduced significantly in extension phase. It was suggested that PCL creep might be one of risk factors to the knee injury in sports activity.  相似文献   

19.
《Endocrine practice》2015,21(3):226-230
ObjectiveWe investigated the correlation between the severity of diabetic retinopathy (DR) and carotid intima media thickness (IMT) as a marker of atherosclerosis in patients with type 2 diabetes.MethodsThe study group consisted of 140 normo-tensive Egyptian patients (68 males and 72 females) with type 2 diabetes and DR. Carotid IMT was evaluated using high-resolution B-mode ultrasonography. DR was assessed and graded using colored fundus photography and fundus fluorescein angiography, as either nonproliferative DR (NPDR) or proliferative DR (PDR).ResultsCarotid IMT was greater in patients with PDR compared to those with NPDR (1.094 ± 0.142 mm vs. 0.842 ± 0.134 mm; P < .001). Carotid IMT showed positive correlation with diabetes duration (P < .01), systolic blood pressure (P < .001), diastolic blood pressure (P < .01), fasting blood glucose (P < .01), postprandial blood glucose (PPBG) (P < .001), glycated hemoglobin (P < .01), total cholesterol (P < .01), triglycerides (TGs) (P < .001), and DR (P < .0001). No significant difference was found between males and females in any of the studied parameters. Multiple regression analysis revealed that the determinants of carotid IMT in the studied group were age (P < .01), PPBG (P < .01), TGs (P < .001), and DR (P < .0001).ConclusionOur study proves that both NPDR and PDR are strong determinants of carotid IMT and atherosclerosis in patients with type 2 diabetes. (Endocr Pract. 2015;21:226-230)  相似文献   

20.
Impact of annealing (ANN) and heat-moisture treatment (HMT) on rapidly digestible starch (RDS), slowly digestible starch (SDS), resistant starch (RS), and expected glycemic index (eGI) of corn, pea, and lentil starches in their native and gelatinized states were determined. ANN was done for 24 h at 70% moisture at temperatures 10 and 15 °C below the onset (To) temperature of gelatinization, while HMT was done at 30% moisture at 100 and 120 °C for 2 h. The swelling factor (SF), amylose leaching (AML) and gelatinization parameters of the above starches before and after ANN and HMT were determined. SF and AML decreased on ANN and HMT (HMT > ANN). The gelatinization temperatures increased on ANN and HMT (HMT > ANN). However, the gelatinization temperature range decreased on ANN but increased on HMT. Birefringence remained unchanged on ANN but decreased on HMT. The Fourier transform infrared (FT-IR) absorbance ratio of 1047 cm?1/1022 cm?1 increased on ANN but decreased on HMT. ANN and HMT increased RDS, RS and eGI levels and decreased SDS levels in granular starches. HMT had a greater impact than ANN on RDS, RS, and SDS levels. In gelatinized starches, ANN and HMT decreased RDS and eGI, but increased SDS and RS levels. These changes were more pronounced on HMT. This study showed that amylopectin structure and interactions formed during ANN and HMT had a significant impact on RDS, SDS, RS and eGI levels of starches.  相似文献   

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