Studies on pH and thermal deactivation of pectolytic enzymes from Aspergillus niger
TL;DR: The addition of protein doubled the half-life times of partially purified PMG, PG I and PG II and the interaction effect of pectolytic enzymes on deactivation was found to be significant.
About: This article is published in Biochemical Engineering Journal.The article was published on 2003-10-01. It has received 108 citations till now.
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TL;DR: It is concluded that Aspergillus niger produces cellulases when grown on medium with pretreated sugarcane bagasse as carbon source and the cellulase complex does not suffer considerable deactivation when stored at -18°C (freezer) for 43 days, however, the activity drops by 40% within 48 hours when storage at 4°C(fridge).
Abstract: Cellulases production by Aspergillus niger and cellulase deactivation kinetic. This work aimed to evaluate the kinetic for the cellulase production by Aspergillus niger and the deactivation kinetic of the cellulase enzymes. Cellulase were produced in three different batches using NaOH 4% (w v -1 ) pre-treated sugarcane bagasse as the carbon source in the fermentation broth. The amount of the bagasse in each batch was 10, 50 and 100 g L -1 . The kinetic of the cellulase production was accomplished by periodically determining the cellulasic activity of the fermentation broth using pre-treated bagasse as the hydrolysis substrate. Changes in the pH also were determined. The cellulase deactivation kinetic was accomplished by periodically determining the cellulasic activity of the fermentation broth samples stored at 4°C and at -18oC. One may conclude that Aspergillus niger produces cellulases when grown on medium with pretreated sugarcane bagasse as carbon source. The ideal time to collect the enzymatic broth was about seven days with maximum yield of 0.0013 U mL -1 ·h for the batch with 10 g L -1 , and 0.0018 U mL -1 ·h for the batches with 50 and 100 g L -1 . The cellulase complex does not suffer considerable deactivation when stored at -18°C (freezer) for 43 days, however, the activity drops by 40% within 48 hours when stored at 4°C (fridge).
8 citations
TL;DR: This article investigated thermodynamic characteristics, degradation kinetics, colour, and antioxidant capabilities of Oscillatoria sp. (BTA-170) extract powder, the PBPs were thermally treated with various monosaccharides such as glucose, fructose, glucose, and lactose.
Abstract: Phycobiliproteins (PBPs) are natural colourants and antioxidants derived from cyanobacteria. The purity indexes of extracted C-phycocyanin (C-PC), allophycocyanin (A-PC), and phycoerythrin (PE) were 0.98-1.23, 0.78-0.0.96, and 0.85-0.99, respectively. To investigate thermodynamic characteristics, degradation kinetics, colour, and antioxidant capabilities of Oscillatoria sp. (BTA-170) extract powder, the PBPs were thermally treated with various monosaccharides such as glucose, fructose, glucose, and lactose. In comparison to other monosaccharides that can stabilize the degradation of C-PC, A-PC, and PE at higher temperatures, glucose was found to be the most essential supplement. At 85 °C, glucose enhanced the half-life of C-PC from 2.09 to 5.37 h, whereas glucose increased the half-life of A-PC from 4.9 to 13.51 h and PE from 5.57 to 15.77 h. While glucose was added, entropy (S) for C-PC was reduced from −177.82 to −183.25 J/Mol K, for A-PC from −178.24 to −169.61 J/Mol K, and for PE from −176.28 to −170.97 J/Mol K. However, the value of enthalpy (H) was enhanced from 52.37 to 53.20 KJ/Mol, while the values of A-PC and PE were raised from 40.63 to 40.56 KJ/Mol and 40.32 to 41.43 KJ/Mol, respectively. Gibbs free energy (G*) was found in the range of 111.48–118.81KJ/Mol for C-PC, 94.49–101.28 KJ/Mol for A-PC, and 95.79–102.63 KJ/Mol for PE when glucose was added, showing a higher degree of protein stability. When fructose was added, the ΔE values of PBPs were reduced from 13.31 to 6.62 at 85 °C, with the least amount of colour degradation among the monosaccharides. At 85 °C, glucose reduced the IC 50 of PBPs from 30.45 mg/ml to 17.33 mg/ml. The thermal tolerance of monosaccharides for PBPs suggested that they could be a potential source of PBP stabilization in the food industry.
8 citations
TL;DR: The production of laccase was optimized by the application of response surface methodology and was 8-fold and 7.5-fold more in static and low-speed shake conditions, respectively, in an optimal medium composition than in an unoptimized medium.
Abstract: Studies on laccase production by Daedalea flavida were carried out in static and low-speed shake cultures. The enzyme production was reduced drastically at a high speed of shaking. Optimal production conditions are necessary to assess the quality of laccase suitable for a specific application. Thus, the production of laccase was optimized by the application of response surface methodology. Laccase production was 8-fold and 7.5-fold more in static and low-speed shake conditions, respectively, in an optimal medium composition than in an unoptimized medium. Laccase obtained using the optimal culture medium of D. flavida was tested for its stability at different temperatures and pH conditions. The partially purified enzyme was most stable at 30°C and pH 5. The half-life of laccase is 87 min at 60°C and at pH 6. The kinetic and thermodynamic parameters were evaluated for the inactivation of the partially purified laccase. The entropy change of inactivation of the enzyme is least at pH 4.
8 citations
TL;DR: The results indicated that increasing TTC concentration initially increased the TF yield and then decreased it, and the relationship between dehydrogenase activity of A. niger (as measured by TF yield) and cell mass was found to be linear.
Abstract: The effects of triphenyl tetrazolium chloride (TTC) concentration, cell age, and presence of O2 on the dehydrogenase activity of Aspergillus niger as measured by triphenyl formazan (TF) yield were investigated. The results indicated that increasing TTC concentration initially increased the TF yield and then decreased it. The maximum TF yield was observed at a TTC concentration of 30 g/L for young cells (4 d old) and 20 g/L for old cells (12 d old). Conducting the test under anaerobic conditions increased the TF yield. About 18% of the TF produced was converted back into TTC in the presence of oxygen. The relationship between dehydrogenase activity of A. niger (as measured by TF yield) and cell mass was found to be linear. A kinetic model describing the relationship between reaction rate (micromoles of TF formed per hour) and TTC concentration while accounting for substrate inhibition was developed, and the model constants were calculated. The optimum TTC-test conditions for dehydrogenase activity measurement of A. niger were a TTC concentration of 20 g/L, a pH of 9.0, a temperature of 55°C, an incubation time of 3 h, and anaerobic conditions.
7 citations
TL;DR: This study partially characterizes the enzymes’ molecular structures as well as their catalytic performance on different substrates which can be used to improve their potential for lignocellulosic biomass conversion and provides some insight into which parameters should be optimized when application of cel8C, cel12B, and peh28 to biomass conversion is the goal.
Abstract: The high crystallinity of cellulosic biomass myofibrils as well as the complexity of their intermolecular structure is a significant impediment for biofuel production. Cloning of celB-, celC-encoded cellulases (cel12B and cel8C) and peh-encoded polygalacturonase (peh28) from Pectobacterium carotovorum subsp. carotovorum (Pcc) was carried out in our previous study using Escherichia coli as a host vector. The current study partially characterizes the enzymes’ molecular structures as well as their catalytic performance on different substrates which can be used to improve their potential for lignocellulosic biomass conversion. β-Jelly roll topology, (α/α)6 antiparallel helices and right-handed β-helices were the folds identified for cel12B, cel8C, and peh28, respectively, in their corresponding protein model structures. Purifications of 17.4-, 6.2-, and 6.0-fold, compared to crude extract, were achieved for cel12B and cel8C, and peh28, respectively, using specific membrane ultrafiltrations and size-exclusion chromatography. Avicel and carboxymethyl cellulose (CMC) were substrates for cel12B, whereas for cel8C catalytic activity was only shown on CMC. The enzymes displayed significant synergy on CMC but not on Avicel when tested for 3 h at 45 °C. No observed β-glucosidase activities were identified for cel8C and cel12B when tested on p-nitrophenyl-β-d-glucopyranoside. Activity stimulation of 130% was observed when a recombinant β-glucosidase from Pcc was added to cel8C and cel12B as tested for 3 h at 45 °C. Optimum temperature and pH of 45 °C and 5.4, respectively, were identified for all three enzymes using various substrates. Catalytic efficiencies (k
cat/K
m) were calculated for cel12B and cel8C on CMC as 0.141 and 2.45 ml/mg/s respectively, at 45 °C and pH 5.0 and for peh28 on polygalacturonic acid as 4.87 ml/mg/s, at 40 °C and pH 5.0. Glucose and cellobiose were the end-products identified for cel8C, cel12B, and β-glucosidase acting together on Avicel or CMC, while galacturonic acid and other minor co-products were identified for peh28 action on pectin. This study provides some insight into which parameters should be optimized when application of cel8C, cel12B, and peh28 to biomass conversion is the goal.
7 citations
Cites background from "Studies on pH and thermal deactivat..."
...[64] for exo-polygalacturonase from Aspergillus sojae, who suggested that stability of the enzyme might be negatively affected by their purification due to the possible synergistic effect from other proteins found in solution with the desired enzyme components as originally proposed by Naidu and Panda [65]....
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...Naidu GSN, Panda T. Studies on pH and thermal deactivation of pectolytic enzymes from Aspergillus niger....
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Journal Article•
TL;DR: Procedures are described for measuring protein in solution or after precipitation with acids or other agents, and for the determination of as little as 0.2 gamma of protein.
289,852 citations
TL;DR: In this paper, the probability of the activated state is calculated using ordinary statistical mechanics, and the probability multiplied by the rate of decomposition gives the specific rate of reaction, and necessary conditions for general statistical treatment to reduce to the usual kinetic treatment are given.
Abstract: The calculation of absolute reaction rates is formulated in terms of quantities which are available from the potential surfaces which can be constructed at the present time. The probability of the activated state is calculated using ordinary statistical mechanics. This probability multiplied by the rate of decomposition gives the specific rate of reaction. The occurrence of quantized vibrations in the activated complex, in degrees of freedom which are unquantized in the original molecules, leads to relative reaction rates for isotopes quite different from the rates predicted using simple kinetic theory. The necessary conditions for the general statistical treatment to reduce to the usual kinetic treatment are given.
4,718 citations
TL;DR: This review discusses various types of pectinases and their applications in the commercial sector.
1,001 citations