Home About us Contact
|
Home About us Contact | ||
|
|
||
Optimum Temperature (optimum + temperature)
Selected AbstractsBacterial metabolism in small temperate streams under contemporary and future climatesFRESHWATER BIOLOGY, Issue 12 2007KAJ SAND-JENSEN Summary 1. We examined the detailed temperature dependence (0,40 °C) of bacterial metabolism associated with fine sediment particles from three Danish lowland streams to test if temperature dependence varied between sites, seasons and quality of organic matter and to evaluate possible consequences of global warming. 2. A modified Arrhenius model with reversible denaturation at high temperatures could account for the temperature dependence of bacterial metabolism and the beginning of saturation above 35 °C and it was superior to the unmodified Arrhenius model. Both models overestimated respiration rates at very low temperatures (<5 °C), whereas Ratkowsky's model , the square root of respiration , provided an excellent linear fit between 0 and 30 °C. 3. There were no indications of differences in temperature dependence among samples dominated by slowly or easily degradable organic substrates. Optimum temperature, apparent minimum temperature, Q10 -values for 0,40 °C and activation energies of bacterial respiration were independent of season, stream site and degradability of organic matter. 4. Q10 -values of bacterial respiration declined significantly with temperature (e.g. 3.31 for 5,15 °C and 1.43 for 25,35 °C) and were independent of site and season. Q10 -values of bacterial production behaved similarly, but were significantly lower than Q10 -values of respiration implying that bacterial growth efficiency declined with temperature. 5. A regional warming scenario for 2071,2100 (IPCC A2) predicted that mean annual temperatures will increase by 3.5 °C in the air and 2.2,4.3 °C in the streams compared with the control scenario for 1961,1990. Temperature is expected to rise more in cool groundwater-fed forest springs than in open, summer-warm streams. Mean annual bacterial respiration is estimated to increase by 26,63% and production by 18,41% among streams assuming that established metabolism,temperature relationships and organic substrate availability remain the same. To improve predictions of future ecosystem behaviour, we further require coupled models of temperature, hydrology, organic production and decomposition. [source] Chitosan-grafted poly(hydroxyethyl methacrylate- co -glycidyl methacrylate) membranes for reversible enzyme immobilizationJOURNAL OF APPLIED POLYMER SCIENCE, Issue 5 2007M. Yakup Ar Abstract Epoxy group-containing poly(hydroxyethyl methacrylate/glycidyl methacrylate), p(HEMA/GMA), membrane was prepared by UV initiated photopolymerization. The membrane was grafted with chitosan (CH) and some of them were chelated with Fe(III) ions. The CH grafted, p(HEMA/GMA), and Fe(III) ions incorporated p(HEMA/GMA)-CH-Fe(III) membranes were used for glucose oxidase (GOD) immobilization via adsorption. The maximum enzyme immobilization capacity of the p(HEMA/GMA)-CH and p(HEMA/GMA)-CH-Fe(III) membranes were 0.89 and 1.36 mg/mL, respectively. The optimal pH value for the immobilized GOD preparations is found to have shifted 0.5 units to more acidic pH 5.0. Optimum temperature for both immobilized preparations was 10°C higher than that of the free enzyme and was significantly broader at higher temperatures. The apparent Km values were found to be 6.9 and 5.8 mM for the adsorbed GOD on p(HEMA/GMA)-CH and p(HEMA/GMA)-CH-Fe(III) membranes, respectively. In addition, all the membranes surfaces were characterized by contact angle measurements. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3084,3093, 2007 [source] Polyphenol Oxidase from Apple (Malus domestica Borkh. cv Bramley's Seedling): Purification Strategies and CharacterizationJOURNAL OF FOOD SCIENCE, Issue 1 2006Deirdre M. Ni Eidhin ABSTRACT Polyphenol oxidase (PPO) was isolated from Bramley's Seedling apples with 75.7-fold purification and 26.5% recovery by ammonium sulfate precipitation, phenyl sepharose chromatography, ion exchange chromatography, and hydroxyapatite chromatography. Molecular weight was estimated to be about 45 kDa by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS PAGE). Optimum PPO activity was at pH 6.5 and greater than 50% activity was retained during storage for 72 h at pH 5.5 to 6.5. Optimum temperature for activity was 30 °C and the enzyme had residual activity of greater than 50% during storage for 72 h at 20 °C to 30 °C and for 24 h at 40 °C to 50 °C. Of the substrates tested, activity was greatest with 4-methylcatechol followed by catechol, pyrogallol, and (,)epicatechin. The most effective inhibitors tested were sodium metabisulfite and ascorbic acid. [source] A mechanistic investigation into the covalent chemical derivatisation of graphite and glassy carbon surfaces using aryldiazonium saltsJOURNAL OF PHYSICAL ORGANIC CHEMISTRY, Issue 6 2008Poobalasingam Abiman Abstract Modification of carbon materials such as graphite and glassy carbon in bulk quantities using diazonium salts is developed. We used both 4-nitrobenzenediazonium tetrafluoroborate and 1-antharaquinonediazonium chloride to modify graphite and glassy carbon surfaces. Experiments were carried out in the presence and absence of hypophosphorous acid and the mechanism involved in both cases were studied using cyclic voltammetry. The observed peak potentials for both the 4-nitrophenyl and 1-anthraquinonyl modified materials were found to differ depending on whether or not the hypophosphorous acid reducing agent was used. In the absence of hypophosphorous acid the derivatisation reaction was inferred to go through a cationic intermediate, whilst in the presence of the hypophosphorous acid the mechanism likely involves either a purely radical intermediate or a mixture of radical and cationic species. Derivatisation experiments from 5 to 70°C allowed us to determine the optimum derivatisation temperature for both cases, in the presence and absence of hypophosphorous acid. Optimum temperature was 20°C for the former and 35°C for the later. Copyright © 2008 John Wiley & Sons, Ltd. [source] Psychrotolerant and microaerophilic bacteria in boreal groundwaterFEMS MICROBIOLOGY ECOLOGY, Issue 1 2002M.K. Männistö Abstract Growth temperature and microaerophily of 39 phylogenetically different isolates from boreal oxygen-deficient groundwater were studied. Based on growth temperatures, the isolates were mainly psychrotolerant bacteria as 35 grew at 2°C and only three at 35°C. Growth rates in the range of 4,35°C fitted the Ratkowsky square root model well. Optimum temperatures of the groundwater isolates varied between 18 and 30°C. In semisolid glucose and PYGV media, 59% and 28% of the isolates, respectively, preferred microaerophilic growth and 33% were catalase-negative. The microaerophilic isolates had the highest sensitivity to H2O2 whereas sensitivity to the superoxide generator paraquat was similar among microaerophilic and aerobic isolates. The results show that the cold (6,8°C) and oxygen-deficient groundwater harbors psychrotolerant and microaerophilic bacteria of different phylogenetic origins which are well adapted to their environment. [source] Optimization of Operating Temperature for Continuous Immobilized Glucose Isomerase Reactor with Pseudo Linear KineticsENGINEERING IN LIFE SCIENCES (ELECTRONIC), Issue 5 2004N.M. Faqir Abstract In this work, the optimal operating temperature for the enzymatic isomerization of glucose to fructose using a continuous immobilized glucose isomerase packed bed reactor is studied. This optimization problem describing the performance of such reactor is based on reversible pseudo linear kinetics and is expressed in terms of a recycle ratio. The thermal deactivation of the enzyme as well as the substrate protection during the reactor operation is considered. The formulation of the problem is expressed in terms of maximization of the productivity of fructose. This constrained nonlinear optimization problem is solved using the disjoint policy of the calculus of variations. Accordingly, this method of solution transforms the nonlinear optimization problem into a system of two coupled nonlinear ordinary differential equations (ODEs) of the initial value type, one equation for the operating temperature profile and the other one for the enzyme activity. The ODE for the operating temperature profile is dependent on the recycle ratio, operating time period, and the reactor residence time as well as the kinetics of the reaction and enzyme deactivation. The optimal initial operating temperature is selected by solving the ODEs system by maximizing the fructose productivity. This results into an unconstrained one-dimensional optimization problem with simple bounds on the operating temperature. Depending on the limits of the recycle ratio, which represents either a plug flow or a mixed flow reactor, it is found that the optimal temperature of operation is characterized by an increasing temperature profile. For higher residence time and low operating periods the residual enzyme activity in the mixed flow reactor is higher than that for the plug flow reactor, which in turn allows the mixed flow reactor to operate at lower temperature than that of the plug flow reactor. At long operating times and short residence time, the operating temperature profiles are almost the same for both reactors. This could be attributed to the effect of substrate protection on the enzyme stability, which is almost the same for both reactors. Improvement in the fructose productivity for both types of reactors is achieved when compared to the constant optimum temperature of operation. The improvement in the fructose productivity for the plug flow reactor is significant in comparison with the mixed flow reactor. [source] Biochemical characterization and inhibitor discovery of shikimate dehydrogenase from Helicobacter pyloriFEBS JOURNAL, Issue 20 2006Cong Han Shikimate dehydrogenase (SDH) is the fourth enzyme involved in the shikimate pathway. It catalyzes the NADPH-dependent reduction of 3-dehydroshikimate to shikimate, and has been developed as a promising target for the discovery of antimicrobial agent. In this report, we identified a new aroE gene encoding SDH from Helicobacter pylori strain SS1. The recombinant H. pylori shikimate dehydrogenase (HpSDH) was cloned, expressed, and purified in Escherichia coli system. The enzymatic characterization of HpSDH demonstrates its activity with kcat of 7.7 s,1 and Km of 0.148 mm toward shikimate, kcat of 7.1 s,1 and Km of 0.182 mm toward NADP, kcat of 5.2 s,1 and Km of 2.9 mm toward NAD. The optimum pH of the enzyme activity is between 8.0 and 9.0, and the optimum temperature is around 60 °C. Using high throughput screening against our laboratory chemical library, five compounds, curcumin (1), 3-(2-naphthyloxy)-4-oxo-2-(trifluoromethyl)-4H -chromen-7-yl 3-chlorobenzoate (2), butyl 2-{[3-(2-naphthyloxy)-4-oxo-2-(trifluoromethyl)-4H -chromen-7-yl]oxy}propanoate (3), 2-({2-[(2-{[2-(2,3-dimethylanilino)-2-oxoethyl]sulfanyl}-1,3-benzothiazol-6-yl)amino]-2-oxoethyl}sulfanyl)- N -(2-naphthyl)acetamide (4), and maesaquinone diacetate (5) were discovered as HpSDH inhibitors with IC50 values of 15.4, 3.9, 13.4, 2.9, and 3.5 µm, respectively. Further investigation indicates that compounds 1, 2, 3, and 5 demonstrate noncompetitive inhibition pattern, and compound 4 displays competitive inhibition pattern with respect to shikimate. Compounds 1, 4, and 5 display noncompetitive inhibition mode, and compounds 2 and 3 show competitive inhibition mode with respect to NADP. Antibacterial assays demonstrate that compounds 1, 2, and 5 can inhibit the growth of H. pylori with MIC of 16, 16, and 32 µg·mL,1, respectively. This current work is expected to favor better understanding the features of SDH and provide useful information for the development of novel antibiotics to treat H. pylori -associated infection. [source] Identification of RNase HII from psychrotrophic bacterium, Shewanella sp.FEBS JOURNAL, Issue 10 2006SIB1 as a high-activity type RNase H The gene encoding RNase HII from the psychrotrophic bacterium, Shewanella sp. SIB1 was cloned, overexpressed in Escherichia coli, and the recombinant protein was purified and biochemically characterized. SIB1 RNase HII is a monomeric protein with 212 amino acid residues and shows an amino acid sequence identity of 64% to E. coli RNase HII. The enzymatic properties of SIB1 RNase HII, such as metal ion preference, pH optimum, and cleavage mode of substrate, were similar to those of E. coli RNase HII. SIB1 RNase HII was less stable than E. coli RNase HII, but the difference was marginal. The half-lives of SIB1 and E. coli RNases HII at 30 °C were ,,30 and 45 min, respectively. The midpoint of the urea denaturation curve and optimum temperature of SIB1 RNase HII were lower than those of E. coli RNase HII by ,,0.2 m and ,,5 °C, respectively. However, SIB1 RNase HII was much more active than E. coli RNase HII at all temperatures studied. The specific activity of SIB1 RNase HII at 30 °C was 20 times that of E. coli RNase HII. Because SIB1 RNase HII was also much more active than SIB1 RNase HI, RNases HI and HII represent low- and high-activity type RNases H, respectively, in SIB1. In contrast, RNases HI and HII represent high- and low-activity type RNases H, respectively, in E. coli. We propose that bacterial cells usually contain low- and high-activity type RNases H, but these types are not correlated with RNase H families. [source] Functional properties of the protein disulfide oxidoreductase from the archaeon Pyrococcus furiosusFEBS JOURNAL, Issue 16 2004A member of a novel protein family related to protein disulfide-isomerase Protein disulfide oxidoreductases are ubiquitous redox enzymes that catalyse dithiol,disulfide exchange reactions with a CXXC sequence motif at their active site. A disulfide oxidoreductase, a highly thermostable protein, was isolated from Pyrococcus furiosus (PfPDO), which is characterized by two redox sites (CXXC) and an unusual molecular mass. Its 3D structure at high resolution suggests that it may be related to the multidomain protein disulfide-isomerase (PDI), which is currently known only in eukaryotes. This work focuses on the functional characterization of PfPDO as well as its relation to the eukaryotic PDIs. Assays of oxidative, reductive, and isomerase activities of PfPDO were performed, which revealed that the archaeal protein not only has oxidative and reductive activity, but also isomerase activity. On the basis of structural data, two single mutants (C35S and C146S) and a double mutant (C35S/C146S) of PfPDO were constructed and analyzed to elucidate the specific roles of the two redox sites. The results indicate that the CPYC site in the C-terminal half of the protein is fundamental to reductive/oxidative activity, whereas isomerase activity requires both active sites. In comparison with PDI, the ATPase activity was tested for PfPDO, which was found to be cation-dependent with a basic pH optimum and an optimum temperature of 90 °C. These results and an investigation on genomic sequence databases indicate that PfPDO may be an ancestor of the eukaryotic PDI and belongs to a novel protein disulfide oxidoreductase family. [source] Expression of penicillin G acylase from the cloned pac gene of Escherichia coli ATCC11105FEBS JOURNAL, Issue 5 2001Effects of pacR, temperature The structural gene pac in Eschericia coli ATCC11105 encodes penicillin G acylase (PGA). Within the pac gene, there is a regulatory gene pacR, which is transcribed in the opposite direction. Site-directed mutagenesis was performed at base 1045 of pac by replacing a T with a C. This substitution did not alter the amino-acid sequence of PGA, but changed the translation start codon of pacR from AUG to GUG. The expression of the mutant pacR decreased dramatically and the lacZ transcriptional fusion analysis showed that GUG was an extremely poor initiation codon for pacR. The pacR mutation caused PGA expression to be constitutive rather than inductive in two strains (E. coli A56, DH10B). The pac inducer phenylacetic acid (PAA) gave significant induction of PGA production at a concentration of 0.2% in wild type, but PAA at this concentration inhibited both cell growth and PGA production in the pacR mutated strains. The temperature-dependent expression character of pac is preserved in the pacR translation-initiation mutant and the optimum temperature of PGA production was 22 °C in both wild type and mutant. At a higher temperature of 37 °C, the PGA precursor polypeptide could not be matured into subunits and formed inclusion bodies, as revealed by western blot analysis. Our investigations confirmed the hypothesis of pacR-mediated PAA induction for PGA expression and clarified the inhibitory effect of high temperature upon the post-translational processing of the PGA precursor polypeptide. [source] Dissimilatory ferrous iron oxidation at a low pH: a novel trait identified in the bacterial subclass RubrobacteridaeFEMS MICROBIOLOGY LETTERS, Issue 2 2008Christopher G. Bryan Abstract A novel iron-oxidizing acidophilic actinobacterium was isolated from spoil material at an abandoned copper mine. Phylogenetic analysis placed the isolate within the Rubrobacteridae subclass of the Actinobacteria. Its optimum temperature and pH for growth are 30,35 °C and pH 3.0, respectively. Although it could catalyze the dissimilatory oxidation of ferrous iron, growth yields declined progressively in media containing ferrous iron concentrations >100 ,M. The isolate, Pa33, did not grow or oxidize iron in the absence of organic carbon, and appeared to be an obligate heterotroph. Specific rates of iron oxidation were much smaller than those determined for the autotrophic iron-oxidizing proteobacterium Acidithiobacillus ferrooxidans and the heterotrophic iron-oxidizing actinobacterium Ferrimicrobium acidiphilum. Iron oxidation by isolate Pa33 appears to be a defensive mechanism, in which iron oxidation converts a soluble species to which the bacterium is sensitive to an oxidized species (ferric iron) that is highly insoluble in the spoil from which it was isolated. This is the first report of acidophily or dissimilatory iron oxidation within the Rubrobacteridae subclass and one of very few within the Actinobacteria phylum as a whole. [source] The effect of ocean acidification and temperature on the fertilization and embryonic development of the Sydney rock oyster Saccostrea glomerata (Gould 1850)GLOBAL CHANGE BIOLOGY, Issue 9 2009LAURA M. PARKER Abstract This study investigated the synergistic effects of ocean acidification (caused by elevations in the partial pressure of carbon dioxide pCO2) and temperature on the fertilization and embryonic development of the economically and ecologically important Sydney rock oyster, Saccostrea glomerata (Gould 1850). As pCO2 increased, fertilization significantly decreased. The temperature of 26 °C was the optimum temperature for fertilization, as temperature increased and decreased from this optimum, fertilization decreased. There was also an effect of pCO2 and temperature on embryonic development. Generally as pCO2 increased, the percentage and size of D-veligers decreased and the percentage of D-veligers that were abnormal increased. The optimum temperature was 26 °C and embryonic development decreased at temperatures that were above and below this temperature. Abnormality of D-veligers was greatest at 1000 ppm and 18 and 30 °C (,90%) and least at 375 ppm and 26 °C (,4%). Finally prolonged exposure of elevated pCO2 and temperature across early developmental stages led to fewer D-veligers, more abnormality and smaller sizes in elevated CO2 environments and may lead to lethal effects at suboptimal temperatures. Embryos that were exposed to the pCO2 and temperature treatments for fertilization and embryonic development had fewer D-veligers, greater percentage of abnormality and reduced size than embryos that were exposed to the treatments for embryonic development only. Further at the elevated temperature of 30 °C and 750,1000 ppm, there was no embryonic development. The results of this study suggest that predicted changes in ocean acidification and temperature over the next century may have severe implications for the distribution and abundance of S. glomerata as well as possible implications for the reproduction and development of other marine invertebrates. [source] Development and growth characteristics of Caucasian and white clover seedlings, compared with perennial ryegrassGRASS & FORAGE SCIENCE, Issue 4 2006A. D. Black Abstract Seedling competition for resources during establishment affects the potential success of individual species within a pasture. Germination, emergence and leaf expansion are key characteristics that contribute to the competitive ability of species. In this study, development and growth characteristics of Caucasian clover, white clover and perennial ryegrass (PRG) seedlings were quantified. A base temperature of <4°C and an optimum temperature of ,27°C were found for development in each species. Thermal time (Tt) requirements for 75% of final germination were lower for Caucasian clover (46°C d) and white clover (40°C d) than for PRG (76°C d), but Tt requirements for 50% of final emergence were similar (,110°C d). The phyllochron (°C d leaf,1) for primary stem leaves was slower for Caucasian clover (109°C d) than for white clover (94°C d) and PRG (101°C d). Appearance of the first PRG tiller, which indicates the initiation of secondary leaf development, occurred after 373°C d, compared with 532°C d for the first white clover stolon. Caucasian clover crown shoots did not develop until >1180°C d. Consequently, white clover and PRG had more leaves (,15 plant,1) and faster shoot relative growth rates (,0·062 mg mg,1 d,1) than Caucasian clover (5 leaves plant,1, 0·049 mg mg,1 d,1). [source] Some properties of polyphenol oxidase from lilyINTERNATIONAL JOURNAL OF FOOD SCIENCE & TECHNOLOGY, Issue 1 2008Ying Yang Summary A study of crude polyphenol oxidase (PPO) from lily bulbs was carried out to provide information useful for guiding food processing operations. Optimum pH for the enzyme activity in the presence of catechol, were 4.0 and 7.0 at room temperature(approximately 20 °C) and the enzyme was stable in the pH range from 5.0 to 6.5 at 4 °C for 10 h. Its optimum temperature was 40 °C and the heat inactivation of the enzyme followed first-order kinetics. Lily PPO possessed a diphenolase activity toward catechol, catechin and gallic acid; catechin was the best substrate for the enzyme considering the Vmax/Km ratio. The most effective enzyme inhibitor was sodium sulphite, although ascorbic acid, l -cysteine and thiourea were also effective inhibitors at high concentration. But NaCl and citric acid were poor inhibitors of the enzyme. Data generated by this study might help to better prevent lily bulbs browning. [source] The effect of low-temperature blanching on the quality of fresh and frozen/thawed mashed potatoesINTERNATIONAL JOURNAL OF FOOD SCIENCE & TECHNOLOGY, Issue 5 2006Cristina Fernández Summary The effect of low-temperature blanching (LTB) prior to cooking on colour, textural, firmness and oscillatory parameters, sensory attributes and overall acceptability of either fresh or frozen/thawed mashed potatoes was studied using response surface methodology (RSM) to establish the optimum temperature and time for blanching in both types of mashed potatoes. A central composite rotatable design was used to study the effects of variation in levels of blanching temperature (57.93,72.07 °C) and time (15.86,44.14 min) on the quality parameters. Stationary points showing maximum thickening had critical temperatures (approximately 67,69 °C) and times (approximately 26,30 min) in the ranges of temperature and time used for each independent variable for both fresh and frozen/thawed mashed potato. Results showed a high correlation between structural reinforcement and overall acceptability under optimum experimental blanching conditions. This demonstrates the potential of this experimental approach in terms of tailoring physical properties to predetermined levels in order to meet consumer preferences in mashed potatoes, and of altering the changes that occur after freezing and thawing. [source] Covalent immobilization of ,-galactosidase on carrageenan coated with chitosanJOURNAL OF APPLIED POLYMER SCIENCE, Issue 1 2009Magdy M.M. Elnashar Abstract ,-Galactosidase was covalently immobilized to carrageenan coated with chitosan for the hydrolysis of lactose. The chitosan-carrageenan polyelectrolyte interaction was found to be dependent on the chitosan pH. At pH 4, the chitosan reached its maximum binding of 28.5% (w/w) where the chitosan surface density was 4.8 mg chitosan/cm2 g of carrageenan gel disks, using Muzzarelli method. Glutaraldehyde was used as a mediator to incorporate new functionality, aldehydic carbonyl group, to the bio-polymers for covalent attachment of ,-galactosidase. The enzyme was covalently immobilized to the biopolymer at a concentration of 2.73 mg protein per g of wet gel. FTIR proved the incorporation of the aldehydic carbonyl group to the carrageenan coated with chitosan at 1720 cm,1. The optimum time for enzyme immobilization was found to be 16 h, after which a plateau was reached. The enzyme loading increased from 2.65 U/g (control gel) to 10.92 U/g gel using the covalent technique. The gel's modification has shown to improve the carrageenan gel thermal stability as well as the immobilized enzyme. For example, the carrageenan gel treated with chitosan showed an outstanding thermal stability at 95°C compared with 35°C for the untreated carrageenan gel. Similarly, the immobilization process shifted the enzyme's optimum temperature from 50°C for the free enzyme towards a wider temperature range 45,55 °C indicating that the enzyme structure is strengthened by immobilization. In brief, the newly developed immobilization method is simple; the carrier is cheap, yet effective and can be used for the immobilization of other enzymes. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 [source] Purification and characterization of an organic solvent and detergent-tolerant novel protease produced by Bacillus sp.JOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 11 2008Abstract BACKGROUND: Purification and characterization of a novel protease produced by Bacillus sp. RKY3, has been investigated, with special emphasis on the stability of the enzyme in the presence of different oxidizing and reducing agents as well as organic solvents. The enzyme was purified in two steps through concentration of the crude enzyme by ammonium sulfate precipitation, followed by anion exchange chromatography. RESULTS: The purified protease had a molecular mass of approximately 38 kDa, which was highly active over a broad range of pH between 7.0 and 9.0 and was also stable over a wide pH range from 5.0 to 11.0. Although the optimum temperature for enzyme activity was found to be 60 °C, it was rapidly deactivated at temperatures above 60 °C. It also showed good stability at 50 °C, with a 70 min half-life. Ca2+ ions did not greatly enhance the activity or the stability of the enzyme. PMSF (1 mmol L,1) completely inhibited the protease activity, and thus the purified protease was considered to be serine protease. The purified protease was stable with oxidants (H2O2, 2%), reducing agents (sodium dodecyl sulfate, 2%), and organic solvents (25%) such as benzene, hexane, and toluene. CONCLUSION: The purified enzyme, protease, seems to possess potential applications in protease-based detergent and bleaching industries. The enzymatic activity against a wide variety of substrates suggests that the purified enzyme should be investigated for a range of commercial applications, especially for soy protein and gelatin hydrolysis in the food processing industry. Copyright © 2008 Society of Chemical Industry [source] PARTIAL PURIFICATION AND CHARACTERIZATION OF A THERMOSTABLE TRYPSIN FROM PYLORIC CAECA OF TAMBAQUI (COLOSSOMA MACROPOMUM)JOURNAL OF FOOD BIOCHEMISTRY, Issue 3 2001RANILSON S. BEZERRA ABSTRACT A 38.5 kDa alkaline protease from pyloric caeca of tambaqui (Colossoma macropomumj, a tropical freshwater fish, was partially purified in three steps: thermal treatment (45Cfor 30 min), salting-out (ammonium sulfate at 40,80% of saturation) and gel filtration (Sephadex G-75), The purification and yield were 51.2-fold and 40%, respectively. The effects of pH, temperature, inhibitors, and substrates on proteolytic activities of partially purified enzyme were investigated. The optimum pH was 9.5, while the optimum temperature was 60C. This alkaline proteolytic activity remained unaltered after 30 min incubation at 55C. Active site inhibition provided additional evidence that this activity is attributed to a trypsin-like enzyme. [source] A Thermostable Chitinase with Chitin-Binding Activity from Phaseolus limensisJOURNAL OF FOOD SCIENCE, Issue 6 2008S.Y. Wang ABSTRACT:, A 28.6-kDa chitinase with chitin-binding activity was isolated from the large lima bean (Phaseolus limensis) seeds. The procedure entailed extraction, ammonium sulfate precipitation, affinity chromatography on Affi-gel blue gel, and high-performance liquid chromatography (HPLC) on SP-Toyopearl. There was an almost 108-fold increase in specific activity of the purified chitinase compared with that of the crude extract. The enzyme exhibited a pI of 7.8 by isoelectric focusing electrophoresis. The optimum pH and the optimum temperature for activity toward N-acetyld-glucosamine were 5.4 and 40 to 50 °C, respectively. The enzyme was stable up to 55 °C. It exerted a potent inhibitory action toward fungal species, including Fusarium solani, Pythium aphanidermatum, and Sclerotium rolfsii. [source] Purification and Characteristics of Feruloyl Esterase from Aspergillus awamori G-2 StrainJOURNAL OF FOOD SCIENCE, Issue 6 2008M. Kanauchi ABSTRACT:, For food industry production processes and other uses, a mold that produces high levels of feruloyl esterase was obtained from laboratory mold collections and other sources. It was Aspergillus awamori G-2 that produces high levels of feruloyl esterase. The feruloyl esterase was purified using ion-exchange chromatography, size-exclusion chromatography, and HPLC chromatography. The enzyme was identified as a monomer protein using size-exclusion chromatography. Its optimum temperature and pH were, respectively, 40 °C and pH 5. Its activity was stable at pH 3 to 5. The enzyme was combined with xylan and starch, but it was absorbed by cellulose. The km of the feruloyl esterase was 0.0019% (0.01 mM). The enzyme showed stable activity at pH 3 and 50 °C, making this enzyme useful for food production. [source] Physicochemical Properties of Cellulose Selectively Oxidized with the 2,2,6,6-Tetramethyl-1-Piperidinyl Oxoammonium IonJOURNAL OF FOOD SCIENCE, Issue 5 2007D.S. Suh ABSTRACT:, This study examined the characteristics of the oxidation reaction on the primary alcohol groups in cellulose involving the 2,2,6,6-tetramethyl-1-piperidinyl oxoammonium ion (TEMPO) and determined the optimum conditions for the preparation of oxidized cellulose (OC). The applicability of OC in polysaccharide systems was also investigated. The effects of TEMPO, sodium bromide (NaBr), and temperature on the oxidation reaction time, yield, and selectivity for primary alcohol groups were examined using response surface methodology (RSM). The reaction time decreased with increases in the temperature and the levels of TEMPO and NaBr. The yield increased with the level of NaBr and decreased as the temperature increased. Selectivity increased with the temperature and decreased as the levels of TEMPO and NaBr increased. The optimum levels of TEMPO and NaBr and the optimum temperature for the production of OC were determined as 0.3 mM/100 mM anhydroglucose unit (AGU), 50 mM/100 mM AGU, and 25 °C, respectively. The water and oil binding capacity and viscosity of cellulose increased with oxidation. Wheat starch containing OC exhibited a decreased initial pasting temperature and setback, but increased peak viscosity, gelatinization, and retrogradation enthalpy (,H). The hardness of the wheat starch gel decreased significantly upon the addition of OC. [source] Polyphenol Oxidase from Bean Sprouts (Glycine max L.)JOURNAL OF FOOD SCIENCE, Issue 1 2003T. Nagai ABSTRACT: Polyphenol oxidase (PPO) was purified and characterized from bean sprouts by ammonium sulfate precipitation, DEAE-Toyopearl 650M, CM-Toyopearl 650M, SuperQ-Toyopearl 650S and QAE-Toyopearl 550C column chromatographies. Substrate staining of the crude extract on electrophoresis showed the presence of 2 isozymic forms of this enzyme. The molecular weight of the purified enzyme was estimated to be about 54 kDa. The optimum pH was 9.0 and optimum temperature 40 °C. Heat inactivation occurred about 30 °C. PPO showed activity to catechol, pyrogallol and dopamine. These compounds such as ascorbic acid, L-cysteine, 2-mercaptoethanol, and glutathione used was the effective inhibitor. Enzyme activity was maintained for 7 d at 4 °C but suddenly decreased after 8 d. [source] Withania somnifera (Ashwagandha): a Novel Source of L-asparaginaseJOURNAL OF INTEGRATIVE PLANT BIOLOGY, Issue 2 2009Vishal P. Oza Abstract Different parts of plant species belonging to Solanaceae and Fabaceae families were screened for L-asparaginase enzyme (E.C.3.5.1.1.). Among 34 plant species screened for L-asparaginase enzyme, Withania somnifera L. was identified as a potential source of the enzyme on the basis of high specific activity of the enzyme. The enzyme was purified and characterized from W. somnifera, a popular medicinal plant in South East Asia and Southern Europe. Purification was carried out by a combination of protein precipitation with ammonium sulfate as well as Sephadex-gel filtration. The purified enzyme is a homodimer, with a molecular mass of 72 ± 0.5 kDa as estimated by sodium dodecyl sulfate-polyacrylamide gel electrophoresisand size exclusion chromatography. The enzyme has a pH optimum of 8.5 and an optimum temperature of 37 °C. The Km value for the enzyme is 6.1 × 10,2 mmol/L. This is the first report for L-asparaginase from W. somnifera, a traditionally used Indian medicinal plant. [source] Endopeptidase Isoenzyme Characteristics in Cucumis sativus Leaves During Dark-induced SenescenceJOURNAL OF INTEGRATIVE PLANT BIOLOGY, Issue 4 2007Peng Zhang Abstract The changes and characteristics of endopeptidase (EP) isoenzymes in cucumber (Cucumis sativus L.) leaves during dark-induced senescence were investigated by activity staining after gradient-polyacrylamide gel electrophoresis (G-PAGE) containing co-polymerized gelatin as substrate. The results showed that both the chlorophyll and the protein contents of leaves were decreased, and the protein degradation was correlated with the increase of proteolytic activity during the course of leaf senescence. Meanwhile, nine cucumber endopeptidases isoenzymes (CEP) with 140, 120, 106, 94, 76, 55, 46, 39 and 35 kDa molecular weights were detected. Four of these, CEP2, 3, 4 and CEP9 appeared all the time, but the changes of the activity were different during incubation. Another four CEPs (CEP5, 6, 7 and CEP8) whose activities increased with dark-induced time were only detected in senescent leaves. Furthermore, the biochemical properties of these nine CEP were also characterized. All the CEPs had high activities from 35 °C to 45 °C, and the optimum temperature was found to be 40 °C. However, the activities of CEPs were not detected below 25 °C or over 60 °C. The activity bands appeared at a wide range of pH from 5.0 to 9.0, but the optimum pH was found at 7.0. No CEPs were detected at pH 4 or pH 10. By inhibition analysis we concluded that CEP2, 3, 4 and CEP9 were serine endopeptidases and CEP6 was a kind of cysteine protease. It is suggested that serine endopeptidases might play a major role in cucumber leaf senescence, and for the first time, six senescence-related endopeptidases (CEP1, 5, 6, 7, 8 and 9) were found in cucumber leaves. [source] Particle shape manipulation and optimization in cooling crystallization involving multiple crystal morphological formsAICHE JOURNAL, Issue 8 2009Jian Wan Abstract A population balance model for predicting the dynamic evolution of crystal shape distribution is further developed to simulate crystallization processes in which multiple crystal morphological forms co-exist and transitions between them can take place. The new model is applied to derive the optimal temperature and supersaturation profiles leading to the desired crystal shape distribution in cooling crystallization. Since tracking an optimum temperature or supersaturation trajectory can be easily implemented by manipulating the coolant flowrate in the reactor jacket, the proposed methodology provides a feasible closed-loop mechanism for crystal shape tailoring and control. The methodology is demonstrated by applying it to a case study of seeded cooling crystallization of potash alum. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source] Enhancing Electrical Properties in NBT,KBT Lead-Free Piezoelectric Ceramics by Optimizing Sintering TemperatureJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 8 2008Ya-Ru Zhang Conventional sintering of (Na1,xKx)0.5Bi0.5TiO3 (abbreviated as NKBTx, x=18,22 mol%) lead-free piezoelectric ceramics was investigated to clarify the optimal sintering temperature for densification and electrical properties. Both sintered density and electrical properties were sensitive to sintering temperature; particularly, the piezoelectric properties deteriorated when the ceramics were sintered above the optimum temperature. The NKBT20 and NKBT22 ceramics synthesized at 1110°,1170°C showed a phase transition from tetragonal to rhombohedral symmetry, which was similar to the morphotropic phase boundary (MPB). Because of such MPB-like behavior, the highest piezoelectric constant (d33) of about 192 pC/N with a high electromechanical coupling factor (kp) of about 32% were obtained in the NKBT22 ceramics sintered at 1150°C. [source] Crack-Healing Behavior of Liquid-Phase-Sintered Silicon Carbide CeramicsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 3 2003Young-Wook Kim Crack-healing behavior of liquid-phase-sintered (LPS) SiC ceramics has been studied as functions of heat-treatment temperature and crack size. Results showed that heat treatment in air could significantly increase the indentation strength. The heat-treatment temperature has a profound influence on the extent of crack healing and the degree of strength recovery. The optimum heat-treatment temperature depends on the softening temperature of an intergranular phase in each material. After heat treatment at the optimum temperature in air, the crack morphology almost entirely disappeared and the indentation strength recovered to the value of the smooth specimens at room temperature for the investigated crack sizes up to ,200 ,m. In addition, a simple heat treatment of SiC ceramics sintered with Al2O3,Y2O3,CaO at 1100°C for 1 h in air resulted in even further improvement of the strength, to a value of 1054 MPa (,150% of the value of the unindented strength). Crack closure and rebonding of the crack wake due to oxidation of cracked surfaces were suggested as a dominant healing mechanism operating in LPS-SiC ceramics. [source] Comparative study on proteolysis of two species of bigeye snapper, Priacanthus macracanthus and Priacanthus tayenusJOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 9 2003Soottawat Benjakul Abstract Proteolytic activity in muscle from two species of bigeye snapper (Priacanthus macracanthus and Priacanthus tayenus) was studied. Autolysis of mince and washed mince at 50 and 60 °C was compared. Higher degradation of myosin heavy chain was observed in both mince and washed mince from P macracanthus than in those from P tayenus, especially when the incubation time was increased. Autolysis of washed mince from both species was inhibited by soybean trypsin inhibitor, suggesting that myofibril-associated proteases were serine proteases. When sarcoplasmic proteolytic activity in P macracanthus muscle was studied, two activity peaks with an optimum temperature of 60 °C were observed at pH 6.5 and 8.5. The activities of both peaks were mostly inhibited by soybean trypsin inhibitor, suggesting that the major protease was a serine protease. Major sarcoplasmic proteolytic activity in P macracanthus muscle was found at Mr 62 000 on sodium dodecyl sulphate substrate gel. For P tayenus sarcoplasmic proteolytic activity, two activity peaks with an optimum temperature of 60 °C were found at pH 5.0 and 8.5. The pH 5.0 peak activity was effectively inhibited by pepstatin A, while the pH 8.5 peak activity was inhibited by several inhibitors. The results indicated that various sarcoplasmic proteases were present in P tayenus muscle. The two species contained different sarcoplasmic proteases in terms of composition and activity level. P macracanthus muscle generally had higher sarcoplasmic proteolytic activities than P tayenus muscle. Copyright © 2003 Society of Chemical Industry [source] The Properties of Covalently Immobilized Trypsin on Soap-Free P(MMA-EA-AA) Latex ParticlesMACROMOLECULAR BIOSCIENCE, Issue 4 2005Kai Kang Abstract Summary: The covalent immobilization of trypsin onto poly[(methyl methacrylate)- co -(ethyl acrylate)- co -(acrylic acid)] latex particles, produced by a soap-free emulsion polymerization technique, was carried out using the carbodiimide method. The catalytic properties and kinetic parameters, as well as the stability of the immobilized enzyme were compared to those of the free enzyme. Results showed that the optimum temperature and pH for the immobilized trypsin in the hydrolysis of casein were 55,°C and 8.5, both of which were higher than that of the free form. It was found that Km (Michaelis constant) was 45.7 mg,·,ml,1 and Vmax (maximal reaction rate) was 793.0 ,g,·,min,1 for immobilized trypsin, compared to a Km of 30.0 mg,·,ml,1 and a Vmax of 5,467.5 ,g,·,min,1 for free trypsin. The immobilized trypsin exhibited much better thermal and chemical stabilities than its free counterpart and maintained over 63% of its initial activity after reusing ten times. TEM photograph of latex particles after trypsin immobilization. [source] Temperature-dependent development of the parasitoid Tachinaephagus zealandicus on five forensically important carrion fly speciesMEDICAL AND VETERINARY ENTOMOLOGY, Issue 2 2010S. C. VOSS The influences of temperature and host species on the development of the forensically important parasitoid Tachinaephagus zealandicus Ashmead (Hymenoptera: Encyrtidae) were studied at six constant temperatures in the range of 15,30°C. T. zealandicus completed development successfully between 15°C and 27°C on five species of Calliphoridae, Calliphora albifrontalis Malloch, Calliphora dubia Macquart, Lucilia sericata Meigen, Chrysomya rufifacies Macquart and Chrysomya megacephala Fabricius. No adult parasitoids emerged from any of the host species reared at 30°C. Temperature and host species significantly influenced development time, emergence success and progeny size. Development was significantly longer on Ch. megacephala and Ch. rufifacies at 18,24°C and significantly longer on Ch. rufifacies and C. albifrontalis at 15°C and 27°C. Parasitoid emergence success was greatest at 21°C, declined at the temperature extremes (15°C and 27°C) and was significantly lower on Ch. megacephala and Ch. rufifacies than on the three other host species. Progeny numbers per host pupa were highest at 21,24°C, declined on either side of this temperature range and were significantly lower on L. sericata, Ch. rufifacies and Ch. megacephala than on either C. dubia or C. albifrontalis. An effect of host species on sex ratio was only observed at 27°C, at which a higher proportion of T. zealandicus females emerged from Ch. megacephala and Ch. rufifacies than from the other host species. The thermal requirements for development (developmental thresholds, thermal constant, optimum temperature) of T. zealandicus in each host species were estimated using linear and non-linear models. Upper and lower developmental thresholds ranged between 29.90°C and 31.73°C, and 9.73°C and 10.08°C, respectively. The optimum temperature for development was estimated at between 25.81°C and 27.05°C. Given the significant effect of host species on development time, the use of parasitoid,host-specific developmental data in forensic application is recommended. [source] | |||||||||||||||||||||||||||||||