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: In this article, nanostructured tin dioxide materials were used as supports for lipases and for the preparation of nanocomposite catalysts that can be utilized in various environmentally beneficial processes.
9 citations
TL;DR: A detailed in vitro mechanistic study of CwlJ1 expressed in Escherichia coli and its activity against the spore cortical fragments of B. anthracis when added exogenously shines some light on the mechanism of spore germination, and provides increased insight into the development of sporicidal enzyme systems for decontamination of the bacteria.
Abstract: The germination enzyme CwlJ1 plays an important role in degrading the cortex during the germination of Bacillus anthracis spores. However, the specific function and catalytic activity of CwlJ1 remain elusive. Here we report for the first time a detailed in vitro mechanistic study of CwlJ1 expressed in Escherichia coli and its activity against the spore cortical fragments of B. anthracis when added exogenously. CwlJ1 was active on both decoated spores and spore cortical fragments. Through liquid chromatography-mass spectrometry analysis of the digested cortical fragments, we determined that CwlJ1 was a thermostable N-acetylmuramoyl-L-alanine amidase. CwlJ1 mainly recognized large segments of glycan chains in the cortex instead of the minimal structural unit tetrasaccharide, with specificity for muramic acid-δ-lactam-containing glycan chains and preference for the tetrapeptide side chain. Unlike most amidases, CwlJ1 did not appear to contain a divalent cation, as it retained its activity in the presence of EDTA. This study shines some light on the mechanism of spore germination, and provides increased insight into the development of sporicidal enzyme systems for decontamination of B. anthracis and other related bacteria.
9 citations
Cites background from "Studies on pH and thermal deactivat..."
...The highly negative DS‡ indicated that CwlJ1 might undergo compaction during thermal deactivation (Naidu and Panda, 2003)....
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...The highly negative DS indicated that CwlJ1 might undergo compaction during thermal deactivation (Naidu and Panda, 2003)....
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01 Jan 2013
TL;DR: In this article, the authors studied the production of extracellular lipase by solidstate fermentation with different olive cakes varieties including Mary, Shenghe and Yellow from isolated fungi using agro-industries waste such as rice straw, rice barn and wheat straw.
Abstract: The aim of this work was to study the production of extracellular lipase by solidstate fermentation with different olive cakes varieties including Mary, Shenghe and Yellow from isolated fungi using agro-industries waste such as rice straw, rice barn and wheat straw. The highest yields of enzyme were obtained in solidstate fermentation using rice straw as solid substrate in combination with 40% Mary olive cakes as inducer. The initial screening by using Plackett-Burman's design demonstrated that among the tested factors, lactose and ammonium sulfate of the medium significantly (p < 0.05) enhanced the lipase production. Further optimization of lipase production by isolated fungi in solid-state fermentation by applying response surface methodology was achieved, which revealed these as follows: 0.42 (% w/v) for lactose and 0.09 (% w/v) for ammonium sulfate. Also the enzyme kinetics parameters, biochemical properties, thermodynamic of thermal deactivation and deactivation rate constant of enzyme were determined.
9 citations
Cites background from "Studies on pH and thermal deactivat..."
...The half-life of an enzyme is defined as the time required by the enzyme to lose half of its initial activity, which is calculated as: ⁄ (3) The energies and entropies of deactivation can be estimated by making use of absolute reaction rates (Narayana Naidu & Panda, 2003)....
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TL;DR: Aldose reductase (AR) catalyzes the conversion of aldoses to their corresponding polyols in yeasts and filamentous fungi, thus the identification and characterization of ARs from novel strains have gained interest as mentioned in this paper.
Abstract: Aldose reductase (AR) catalyzes the conversion of aldoses to their corresponding polyols in yeasts and filamentous fungi. ARs have the potential to be exploited for the enzymatic production of xylitol, thus the identification and characterization of ARs from novel strains have gained interest. In this study, we chose the novel yeast Debaryomyces nepalensis as a source for an AR gene. For the first time, here we isolated the AR gene from D. nepalensis (DnAR) that encodes a protein of 320 amino acids with a predicted molecular weight of 36.7 kDa using the RACE technique. It was heterologously expressed in Escherichia coli as a His-tagged fusion protein and purified. The enzyme showed strict NADPH dependence and broad substrate specificity with high catalytic efficiency for arabinose, xylose and 3-nitro benzaldehyde. Remarkably, it was active and stable in the presence of high concentrations of salts (KCl/NaCl), thus exhibiting halotolerance. It showed 75% and 45% activity at 0.5 and 1 M concentration of salts respectively. Enzyme half-lifetime at 1 M KCl and 1 M NaCl was found to be 30 h and 16.5 h respectively. Furthermore, to explore the structural basis of its halotolerance, we built a homology model of DnAR. Surprisingly, we found that the existence of a uniform negative electrostatic potential over the protein surface, which is one of the known mechanisms governing protein halotolerance. Therefore, DnAR could be exploited as a biocatalyst to develop an enzyme based bioprocess for xylitol production from lignocelluloses. Moreover, this is the first report providing the genetic sequence and biochemical characteristics of a halotolerant aldose reductase.
9 citations
TL;DR: In this article, a mathematical analysis was proposed to assess if application of the optimal temperature control (OTC) in biotransformations with deactivation of native enzyme is justified.
8 citations
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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