scholarly journals Characterisation of a “green” lipase from Aspergillus niger immobilised on polyethersulfone membranes

2019 ◽  
Vol 42 ◽  
pp. e44498
Author(s):  
Fernanda Martins de Souza ◽  
Cleide Mara Faria Soares ◽  
Alvaro Silva Lima ◽  
Luciana Cristina Lins de Aquino Santana
Keyword(s):  
Thermal Stability ◽  
Aspergillus Niger ◽  
Thermal Inactivation ◽  
Physical Adsorption ◽  
Covalent Bonding ◽  
Point Of View ◽  
Thermal Stabilities ◽  
Optimum Ph ◽  
Hancornia Speciosa ◽  
Free Lipase

In this work, a “green” Aspergillus niger lipase obtained from the solid-state fermentation of Hancornia speciosa (“mangaba”) seeds was efficiently immobilised on polyethersulfone membranes (PES) by physical adsorption (PES-ADS-lipase) and covalent bonding (PES-COV-lipase) (immobilisation yields of 92 and 81%, respectively). The free lipase showed an optimum pH close to neutrality, while the biocatalysts displaced the pH to the alkaline region (optimum pH 9.0 and 11.0 for PES-ADS-lipase and PES-COV-lipase, respectively). The optimum temperature of free lipase was 55°C; however, a higher thermal stability occurred at 37°C. The PES-ADS-lipase and PES-COV-lipase showed lower optimum temperatures (37 and 45°C, respectively) but higher thermal stabilities at 45 and 55°C, respectively. The lower thermal inactivation constant and higher half-life of PES-COV-lipase at 55°C confirmed the efficiency of covalent bonding in maintaining the thermal stability of the enzyme. The Michaelis–Menten constant (Km) and maximum rate of reaction (Vmax) were also determined, and the biocatalysts showed higher affinities to substrates (lower Km values) than free lipase. In this work, the biocatalysts showed good catalytic properties with future potential applications in hydrolysis reactions. The use of a “green” lipase obtained from agroindustrial residue makes this product economically attractive from an industrial point of view.

scholarly journals Immobilization of Isolated Lipase From Moldy Copra(Aspergillus Oryzae)

2011 ◽  
Vol 8 (2) ◽  
pp. 896-902
Author(s):  
Seniwati Dali ◽  
A. B. D. Rauf Patong ◽  
M. Noor Jalaluddin ◽  
Pirman ◽  
Baharuddin Hamzah
Keyword(s):  
Thermal Stability ◽  
Aspergillus Oryzae ◽  
Immobilized Lipase ◽  
Optimum Temperature ◽  
Adsorption Method ◽  
Ph Optimum ◽  
Optimum Ph ◽  
Recovery Technique ◽  
Free Lipase

Enzyme immobilization is a recovery technique that has been studied in several years, using support as a media to help enzyme dissolutions to the reaction substrate. Immobilization method used in this study was adsorption method, using specific lipase fromAspergillus oryzae. Lipase was partially purified from the culture supernatant ofAspergillus oryzae. Enzyme was immobilized by adsorbed on silica gel. Studies on free and immobilized lipase systems for determination of optimum pH, optimum temperature, thermal stability and reusability were carried out. The results showed that free lipase had optimum pH 8,2 and optimum temperature 35 °C while the immobilized lipase had optimum 8,2 and optimum temperature 45 °C. The thermal stability of the immobilized lipase, relative to that of the free lipase, was markedly increased. The immobilized lipase can be reused for at least six times.

scholarly journals Kinetics and thermodynamics of thermal inactivation for recombinant Escherichia coli cellulases, cel12B, cel8C, and polygalacturonase, peh28; biocatalysts for biofuel precursor production

2020 ◽  
Author(s):  
Eman Ibrahim ◽  
Ahmed Mahmoud ◽  
Kim D Jones ◽  
Keith E Taylor ◽  
Ebtesam N Hosseney ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Thermal Stability ◽  
Lignocellulosic Biomass ◽  
Thermal Inactivation ◽  
Biomass Conversion ◽  
Industrial Applications ◽  
Recombinant Escherichia Coli ◽  
Thermal Stabilities ◽  
Kinetics And Thermodynamics ◽  
Lignocellulosic Biomass Conversion

Abstract Lignocellulosic biomass conversion using cellulases/polygalacturonases is a process that can be progressively influenced by several determinants involved in cellulose microfibril degradation. This article focuses on the kinetics and thermodynamics of thermal inactivation of recombinant Escherichia coli cellulases, cel12B, cel8C and a polygalacturonase, peh 28, derived from Pectobacterium carotovorum sub sp. carotovorum. Several consensus motifs conferring the enzymes’ thermal stability in both cel12B and peh28 model structures have been detailed earlier, which were confirmed for the three enzymes through the current study of their thermal inactivation profiles over the 20–80°C range using the respective activities on carboxymethylcellulose and polygalacturonic acid. Kinetic constants and half-lives of thermal inactivation, inactivation energy, plus inactivation entropies, enthalpies and Gibbs free energies, revealed high stability, less conformational change and protein unfolding for cel12B and peh28 due to thermal denaturation compared to cel8C. The apparent thermal stability of peh28 and cel12B, along with their hydrolytic efficiency on a lignocellulosic biomass conversion as reported previously, makes these enzymes candidates for various industrial applications. Analysis of the Gibbs free energy values suggests that the thermal stabilities of cel12B and peh28 are entropy-controlled over the tested temperature range.

scholarly journals Investigation of Optimal Conditions for Production, Characterization, and Immobilization of Fructosyltransferase and β-Fructofuranosidase by Filamentous Fungi

2020 ◽  
Vol 11 (4) ◽  
pp. 11187-11201
Keyword(s):  
Thermal Stability ◽  
Aspergillus Niger ◽  
Kinetic Parameters ◽  
Filamentous Fungi ◽  
Storage Stability ◽  
Optimal Conditions ◽  
Extracellular Production ◽  
Optimum Ph ◽  
Optimum Ph And Temperature ◽  
Penicillium Brasilianum

This work's objective was the extracellular production, partial characterization, and immobilization of the enzymes fructosyltransferase (Ftase) and β-fructofuranosidadase (Ffase) by filamentous fungi. Aspergillus niger ATCC 9642 and Penicillium brasilianum were evaluated for the production of fructosyltransferase (Ftase) and β-fructofuranosidadase (FASE) enzymes. The A. niger presented the highest activity of FTase (24.86 µmol/min.mL) and FFase (28.68 µmol/min.mL) in medium composed of 20% sucrose, 0.5% yeast extract, 1% NaNO3, 0.05% MgSO4.7 H2O, 0.25% KH2PO4, 0.5% NH4Cl and 0.25% NaCl inoculated using 5x107spores/mL and incubated at 25°C, pH 5.5, 150 rpm for 48 h. Presenting optimum pH and temperature of 2.39 and 60°C. Thermal stability has shown that the enzyme FFase is more thermally stable when compared to FTase. Stability against different pHs showed similar behavior for FTase and FFase; the optimum pH being between 2.0 and 3.0. FTase and FFase showed storage stability in freezing and refrigeration temperature for approximately 400 h. The kinetic parameters, Km and Vmax, for the sucrose substrate were 24.60mM and 104.16 μmol/min.mL for FTase and 3.91mM and 20.24 μmol/min.mL for FFase. The immobilization process displayed a yield of 6744.66% for FFase and 3928.90% for FTase, with enzymatic activities of 364.79 U/g and 220.34 U/g, and 4 and 3 times reuse, respectively.

Thermal Inactivation of Avian Liver and Muscle Fructose 1,6-Diphosphatases in the Presence of Fructose 1,6-Diphosphate, AMP, and Divalent Cations

1974 ◽  
Vol 52 (8) ◽  
pp. 670-678 ◽  
Author(s):  
Ronald R. Marquardt ◽  
J. P. Olson
Keyword(s):  
Thermal Stability ◽  
Thermal Inactivation ◽  
Liver Enzymes ◽  
Divalent Cations ◽  
Tris Buffer ◽  
Opposite Pattern ◽  
Thermal Stabilities ◽  
Muscle Enzyme ◽  
Degree Of Protection ◽  
Thermal Stability Of

The effects at various pH levels of fructose 1,6-diphosphate (FDP), AMP, CaCl2, MnCl2, and/or MgCl2 on the thermal stability of pure forms of avian liver and muscle fructose 1,6-diphosphatases were investigated. Both enzymes were more stable when stored at 20 °C than at 2 °C. Maximum stabilities of the two enzymes when incubated at various temperatures in a Tris buffer occurred at approximately pH 6. All of the above compounds when added to a pH 7.5 Tris buffer markedly increased the thermal stabilities of both enzymes. Individually, FDP provided the highest degree of protection for the muscle enzyme whereas MnCl2 was most effective with the liver enzyme; in all cases the degree of protection was concentration dependent. At pH 7.5 combinations of MgCl2, FDP, and AMP were most effective. In the presence of these compounds initial inactivation of the muscle and liver enzymes did not occur until respective temperatures of 74 and 78 °C (15 min) were reached; these compare with initial inactivation temperatures in the absence of these compounds of 55 and 59 °C. The interaction of MgCl2 and FDP with the two enzymes at varying pH levels showed markedly different patterns. At pH7.5 and 8.8 increasing levels of MgCl2 provided increasing levels of protection whereas at pH 6.2 increasing MgCl2 concentrations resulted in an enhanced degree of inactivation. In the presence of FDP an opposite pattern was observed at the various pH levels. The presence of phosphate in the buffer tended to yield results similar to those of FDP.

Thermal Stabilities and the Thermal Degradation Kinetics Study of the Flame Retardant Epoxy Resins

2014 ◽  
Vol 1053 ◽  
pp. 263-267 ◽  
Author(s):  
Xiu Juan Tian
Keyword(s):  
Thermal Stability ◽  
Thermal Degradation ◽  
Flame Retardant ◽  
Epoxy Resin ◽  
Epoxy Resins ◽  
Degradation Kinetics ◽  
Thermal Degradation Kinetics ◽  
Thermal Stabilities ◽  
Degradation Kinetic ◽  
Modified Epoxy

Thermal stability and thermal degradation kinetics of epoxy resins with 2-(Diphenylphosphinyl)-1, 4-benzenediol were investegated by thermogravimetric analysis (TGA) at different heating rates of 5 K/min, 10 K/min, 20 K/min and 40 K/min. The thermal degradation kinetic mechanism and models of the modified epoxy resins were determined by Coast Redfern method.The results showed that epoxy resins modified with the flame retardant had more thermal stability than pure epoxy resin. The solid-state decomposition mechanism of epoxy resin and the modified epoxy resin corresponded to the controlled decelerating ځ˽̈́˰̵̳͂͆ͅ˼˰̴̱̾˰̸̵̈́˰̵̸̳̱̹̽̾̓̽˰̶̳̹̾̈́̿̾̓ͅ˰̶˸ځ˹˰̵̵͇͂˰̃˸́˽ځ˹2/3. The introduction of phosphorus-containing flame retardant reduced thermal degradation rate of epoxy resins in the primary stage, and promote the formation of carbon layer.

Binding of 3-phosphoglycerate leads to both activation and stabilisation of ADP-glucose pyrophosphorylase from apple leaves

2005 ◽  
Vol 32 (9) ◽  
pp. 839
Author(s):  
Rui Zhou ◽  
Lailiang Cheng
Keyword(s):  
Heat Treatment ◽  
Thermal Stability ◽  
Enzyme Activity ◽  
Inorganic Phosphate ◽  
Thermal Inactivation ◽  
Specific Activity ◽  
Apple Leaves ◽  
Apparent Homogeneity ◽  
Adp Glucose Pyrophosphorylase ◽  
High Concentrations

Apple leaf ADP-glucose pyrophosphorylase was purified 1436-fold to apparent homogeneity with a specific activity of 58.9 units mg–1. The enzyme was activated by 3-phosphoglycerate (PGA) and inhibited by inorganic phosphate (Pi) in the ADPG synthesis direction. In the pyrophosphorolytic direction, however, high concentrations of PGA (> 2.5 mm) inhibited the enzyme activity. The enzyme was resistant to thermal inactivation with a T0.5 (temperature at which 50% of the enzyme activity is lost after 5 min incubation) of 52°C. Incubation with 2 mm PGA or 2 mm Pi increased T0.5 to 68°C. Incubation with 2 mm dithiothreitol (DTT) decreased T0.5 to 42°C, whereas inclusion of 2 mm PGA in the DTT incubation maintained T0.5 at 52°C. DTT-induced decrease in thermal stability was accompanied by monomerisation of the small subunits. Presence of PGA in the DTT incubation did not alter the monomerisation of the small subunits of the enzyme induced by DTT. These findings indicate that binding of PGA renders apple leaf AGPase with a conformation that is not only more efficient in catalysis but also more stable to heat treatment. The physiological significance of the protective effect of PGA on thermal inactivation of AGPase is discussed.

Preparation and Properties of Silicon-Containing Arylacetylene Resins with Octa(maleimidophenyl)silsesquioxane

2012 ◽  
Vol 557-559 ◽  
pp. 1152-1156
Author(s):  
Yan Zhou ◽  
Fu Wei Huang ◽  
Fa Rong Huang ◽  
Lei Du
Keyword(s):  
Thermal Stability ◽  
Dielectric Constant ◽  
Dielectric Properties ◽  
Thermal Polymerization ◽  
Curing Process ◽  
Thermal Stabilities ◽  
Curing Reaction ◽  
Air Atmosphere ◽  
Ft Ir ◽  
Dsc Analyses

Modified silicon-containing arylacetylene resins (DMSEPE-OMPS) were prepared from poly(dimethylsilyleneethynylenephenyleneethynylene) (DMSEPE) and Octa(maleimidophenyl)- silsesquioxane (OMPS). The curing reaction of DMSEPE-OMPS resin was studied by FT-IR and DSC techniques. Thermal stability and dielectric properties of cured DMSEPE-OMPS resins were determined. FT-IR and DSC analyses indicate that thermal polymerization of DMSEPE-OMPS resin occurs in the curing process. Thermal stabilities of cured DMSEPE-OMPS resins under N2 and air atmosphere decrease gradually with the increment of OMPS components. The incorporation of OMPS can obviously reduce dielectric constant of DMSEPE-OMPS resins.

Syntheses, Crystal Structures and Thermal Stability of Co(II) and Zn(II) Complexes with Ethyl Carbazate

2005 ◽  
Vol 60 (5) ◽  
pp. 505-510 ◽  
Author(s):  
Tong-Lai Zhang ◽  
Jiang-Chuang Song ◽  
Jian-Guo Zhang ◽  
Gui-Xia Ma ◽  
Kai-Bei Yu
Keyword(s):  
Thermal Stability ◽  
Aqueous Solutions ◽  
Diffraction Analysis ◽  
Single Crystals ◽  
Slow Evaporation ◽  
X Ray Diffraction ◽  
Element Analysis ◽  
Thermal Stabilities ◽  
X Ray ◽  
Thermal Stability Of

Cobalt(II) and zinc(II) complexes of ethyl carbazate (ECZ), [Co(ECZ)3](NO3)2 and [Zn(ECZ)3] (NO3)2, were synthesized. Single crystals of these two compounds were grown from aqueous solutions using a slow evaporation method. Their structures have been determined by X-ray diffraction analysis. Both of them are monoclinic with space group P21/n. The complexes are further characterized by element analysis and IR measurements. Their thermal stabilities are studied by using TG-DTG, DSC techniques. When heated to 350 °C, only metal oxide was left for both complexes.

Simulation of Thermal Stability and Friction: A Lubricant Confined Between Monolayers of Wear Inhibitors on Iron Oxide

1998 ◽  
Vol 543 ◽  
Author(s):  
T. Çağin ◽  
Y. Zhou ◽  
E. S. Yamaguchi ◽  
R. Frazier ◽  
A. Ho ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Thermal Stability ◽  
Quantum Chemical ◽  
Md Simulations ◽  
Atomic Level ◽  
The Self ◽  
Self Assembled Monolayer ◽  
Thermal Stabilities ◽  
Frictional Forces ◽  
Thermal Stability Of

AbstractTo understand antiwear phenomena in motor engines at the atomic level and provide evidence inselecting future ashless wear inhibitors, we studied the thermal stability of the self-assembled monolayer(SAM) model for dithiophosphate (DTP) and dithiocarbamate (DTC) molecules on the iron oxidesurface using molecular dynamics. The interactions for DTP, DTC and Fe2O3 are evaluated based on aforce field derived from fitting to ab initio quantum chemical calculations of dimethyl DTP (and DTC)and Fe(OH)2(H2O)2-DTP (DTC) clusters. MD simulations at constant-NPT are conducted to assesrelative thermal stabilities of the DTP and DTC with different pendant groups (n-propyl, i-propyl, npentyl.and i-pentyl). To investigate frictional process, we employ a steady state MD method, in whichone of the Fe2O3 slabs maintained at a constant linear velocity. We obtain the time averaged normaland frictional forces from the interatomic forces. Then, we calculated the friction coefficient at theinterface between SAMs of DTP and the confined lubricant, hexadecane, to assess the shear stability ofDTPs with different pendant groups.

scholarly journals Pectinase production by Aspergillus niger isolated from decomposed apple skin

2013 ◽  
Vol 48 (1) ◽  
pp. 25-32 ◽  
Author(s):  
S Islam ◽  
B Feroza ◽  
AKMR Alam ◽  
S Begum
Keyword(s):  
Aspergillus Niger ◽  
Incubation Temperature ◽  
Nitrogen Sources ◽  
Inoculum Size ◽  
Point Of View ◽  
Media Composition ◽  
Maximal Level ◽  
Pectinolytic Activity ◽  
Pectinase Activity ◽  
Pectinase Production

Pectinase activity among twelve different fungal strains, Aspergillus niger IM09 was identified as a potential one to produce maximal level 831 U/g at pH 4.0. Media composition, incubation temperature, incubation time, substrate concentration, aeration, inoculum size, assay temperature and nitrogen sources were found to effect pectinase activity. Moisture content did not affect the activity significantly. Media composition was varied to optimize the enzyme production in solid state fermentation. It was observed that the highest pectinase activity of 831.0 U/g was found to produce in presence of yeast extract as a nitrogen source in combination with ammonium sulfate in assay media. Aeration showed positive significant effects on pectinase production 755 U/g at 1000 ml flasks. The highest pectinase production was found at 2 g pectin (521 U/g) used as a substrate. Pectinolytic activity was found to have undergone catabolite repression with higher pectin concentration (205 U/g at 5 g pectin). The incubation period to achieve maximum pectinase activity by the isolated strain Aspergillus niger IM09 was 3 days, which is suitable from the commercial point of view. DOI: http://dx.doi.org/10.3329/bjsir.v48i1.15410 Bangladesh J. Sci. Ind. Res. 48(1), 25-32, 2013

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