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: This is the first report providing information on the thermal deactivation kinetics, thermodynamic parameter estimation and the influence of cofactor on thermal stability of Debaryomyces nepalensis NCYC 3413 xylose reductase.
13 citations
TL;DR: Endo-polygalacturonase (endo-PG) production by Aspergillus niger T0005/007-2 in solid medium with 170 mm of height was evaluated in a cylindrical double surface bioreactor in 96-h experiments and none of the conditions evaluated was efficient for medium temperature control.
Abstract: Endo-polygalacturonase (endo-PG) production by Aspergillus niger T0005/007-2 in solid medium with 170 mm of height was evaluated in a cylindrical double surface bioreactor in 96-h experiments. Cell concentration close to 92 mg.g -1 dm (mg per g of dry medium) in the standard condition (static) was achieved, whereas in tests under forced aeration of 1.4 and 2.8 L.min-1. Kg-1 mm (L of air per minute per Kg of moist medium) and with the central shaft fungal biomass attained approximately 100 mg.g-1 dm. Superior endo-PG activity was obtained with the central-shaft system, 78 U.g-1 dm (units per g of dry medium). Forced aeration and pressure pulse showed no positive effect on the production of endo-PG, 45 U.g-1 dm and 28 U.g-1 dm, respectively. None of the conditions evaluated was efficient for medium temperature control. Endo-PG was stable up to 40oC. The activity decreased in 50% after 120 minutes at 50oC, which is a temperature normally found during this process.
13 citations
Cites background from "Studies on pH and thermal deactivat..."
...The total inactivation of endo-PG was quickly noticed after about 15 minutes at 60 and 70ºC, as reported by Naidu and Panda (2003) for polygalacturonase produced by A. niger in submerged process....
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TL;DR: Inhibition by EDTA and activation by 2-mercaptoethanol demonstrated respectively that the enzyme is a metalloenzyme and required cysteine in the active site, demonstrating its potential for use in the food industry.
Abstract: β-galactosidase from Lactobacillus leichmannii 313 (LL313) was purified (4.5-fold, 11% purification yield), and characterised, giving optimal enzyme activity at pH 5.5 and 55 °C. Thermal inactivation of crude and purified enzyme showed first order inactivation kinetics. Deactivation energy (Ed) of 390.58 ± 34.94 kJ/mol (crude enzyme) and 404.17 ± 46.19 kJ/mol (purified enzyme), based on the Arrhenius equation were not significantly different. Thermal stability, determined by decimal reduction time (D value), z value, and half-life (t1/2) of purified enzyme were significantly lower than those of crude enzyme. This, together with thermodynamic parameters (ΔH#, ΔG# and ΔS#) suggested that the purification procedure affected the thermal stability of the enzyme. The purified enzyme gave Vmax and Km values of 9.15 ± 0.23 mol g−1.min−1 and 2.97 ± 0.32 mM respectively, with ο-nitrophenol-β- d -galactopyranoside as substrate. The purified enzyme was activated by Na+ ions (>1 mM); remained unaffected by K+; and was inhibited by Ca2+ and Mn2+ (1–100 mM). Inhibition by EDTA (1 mM) and activation by 2-mercaptoethanol (1 mM) demonstrated respectively that the enzyme is a metalloenzyme and required cysteine in the active site. The enzyme exhibited hydrolytic and transgalactosylation activities with lactose as substrate, demonstrating its potential for use in the food industry.
12 citations
TL;DR: The purification and physicochemical properties of an endo-polygalacturonase produced by Wickerhamomyces anomalus isolated from the citrus fruit peels were studied and the purified PG was able to macerate cassava tissues.
Abstract: The aim of this work was to study the purification and physicochemical properties of an endo-polygalacturonase (PG) produced by Wickerhamomyces anomalus isolated from the citrus fruit peels The enzyme was purified to homogeneity from the culture filtrate of W anomalus grown on the yeast nitrogen base medium with glucose as carbon and energy source and citrus pectin as inductor After anion-exchange chromatography and gel filtration chromatography, PG activity was eluted as a single peak, yielding 21% of the original activity After dialysis and cation-exchange chromatography, only one fraction with PG activity was obtained, recovering 56% of initial enzyme activity and 13-fold increase in specific activity The molecular weight of the enzyme was estimated as 43 kDa by the SDS-PAGE The enzyme exhibited maximal activity at pH 42 and was stable over a pH range from 35 to 60 and up to 49oC for 10 h The Vmaxand Km values with polygalacturonic acid as substrate were 026 mmol/Lmin and 0173 mg/mL, respectively Cations such as Cu+2, Fe+3, Mg+2, Mn+2 and Zn+2 did not show any significant effect on PG activity but K+ and Ca+2 reduced it The purified PG was able to macerate cassava tissues
11 citations
TL;DR: It was found that phenol showed competitive inhibition of XR whereas gallic acid, vanillin, furfural, 5-hydroxymethylfurfural (HMF) and acetate exhibited mixed inhibition, and the enzyme stability was drastically affected in the presence of phenols.
11 citations
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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