Love words? Need even more definitions? Homophones, Homographs, and Homonyms The same, but different. Merriam-Webster's Words of the Week - Nov. Ask the Editors 'Everyday' vs. What Is 'Semantic Bleaching'? How 'literally' can mean "figuratively".
Literally How to use a word that literally drives some pe Is Singular 'They' a Better Choice? The awkward case of 'his or her'. Take the quiz. In the course of a study on the bacterial degradation of plant cell wall polysaccharides, we observed that growing cells of motile cellulolytic bacteria accumulated, without attachment, near cellulose fibers present in the cultures.
Because it seemed likely that the accumulation was due to chemotactic behavior, we investigated the chemotactic responses of one of the above-mentioned bacteria Cellulomonas gelida ATCC We studied primarily the responses toward cellobiose, which is the major product of cellulose hydrolysis by microorganisms, and toward hemicellulose hydrolysis products. We report here the real-time visualization of cryst.
Trichoderma reesei cellobiohydrolase I TrCel7A mols. Changing the cryst. Treatment of this bulky cryst. Cellulose was completely degraded by the synergistic action between the two enzymes. The Dissociation Mechanism of Processive Cellulases. Vermaas, Josh V. National Academy of Sciences. Cellobiohydrolases CBHs are cellulases capable of liberating many sugar mols. Within the complete processive cycle of CBHs, dissocn.
Here, we present a direct comparison of potential mol. Computational rate ests. We also present the crystal structure of a disulfide variant that covalently links substrate-enclosing loops on either side of the substrate-binding tunnel, which constitutes a CBH that can only dissoc.
A review with refs. The ability and, consequently, the limitations of various microbial enzyme systems to completely hydrolyze the structural polysaccharides of plant cell walls has been the focus of an enormous amt. As more and more of these extracellular enzymic systems are being identified and characterized, clear similarities and differences are being elucidated.
Although much has been learned concerning the structures, kinetics, catalytic action, and interactions of enzymes and their substrates, no single mechanism of total lignocellulosic saccharification has been established. The heterogeneous nature of the supramol. This present review is not intended to conclusively answer what factors control polysaccharide biodegrdn. An amperometric biosensor for the detection of cellobiose has been introduced to study the kinetics of enzymic hydrolysis of cryst.
By use of a sensor in which pyrroloquinoline quinone-dependent glucose dehydrogenase was immobilized on the surface of electrode, direct and continuous observation of the hydrolysis can be achieved even in a thick cellulose suspension.
The steady-state rate of the hydrolysis increased with increasing concns. The exptl. The catalytic const. Academic Press. Used in conjugation with an FIA system this biosensor can replace colorimetric assays for measuring cellobiose liberated from cellulose in a series of cellulase-contg. The biosensor gave the same result as the Somogyi-Nelson method in a less time-consuming and laborious manner. The two methods showed about the same precision. A methodol. Antibodies raised against a amino acid synthetic peptide with sequence taken from the cohesin domain of the scaffoldin protein of Clostridium thermocellum ATCC were used to develop an indirect ELISA protocol.
Six cellulase calibration stds. All six stds. Cell concn. Two alternative methods appeared to overpredict the cell concn. Cellulase protein prodn. It is concluded that the reported protocols establish a reasonable methodol. An amperometric enzyme biosensor for continuous detection of cellobiose has been implemented as an enzyme assay for cellulases.
We show that the initial kinetics for cellobiohydrolase I, Cel7A from Trichoderma reesei, acting on different types of cellulose substrates, semi-cryst. PcCDH was cross-linked and immobilized on the surface of a carbon paste electrode which contained a mediator, benzoquinone.
An oxidn. The CDH-biosensors showed high sensitivity The response from the CDH-biosensor during enzymic hydrolysis was cor. It is suggested that quant. Enzyme Microb. A novel electrochem. The enzyme biosensor was constructed with pyranose dehydrongease PDH from Agaricus meleagris that was immobilized on the surface of a carbon paste electrode, which contained the mediator 2,6-dichlorophenolindophenol DCIP.
The PDH-biosensor was shown to be anomer unspecific and it can therefore be used in kinetic studies over broad time-scales of both retaining- and inverting cellulases in addn. The biosensor was used for real-time measurements of the activity of the inverting cellobiohydrolase Cel6A from Hypocrea jecorina HjCel6A on cellulosic substrates with different morphol.
The steady-state rate of hydrolysis increased towards a satn. Conversely, the substrate load at half-satn. Biosensors covered with a polycarbonate membrane showed high operational stability of several weeks with daily use. American Society for Biochemistry and Molecular Biology. Lytic polysaccharide monooxygenase LPMO represents a unique principle of oxidative degrdn. Used in combination with hydrolytic enzymes, LPMO appears to constitute a significant factor of the efficiency of enzymic biomass depolymn.
LPMO activity on different cellulose substrates has been shown from the slow release of oxidized oligosaccharides into soln. The specificity of LPMO for degrading ordered cryst. Here, the authors show by fluorescent dye adsorption analyzed with confocal laser scanning microscopy that a LPMO from Neurospora crassa introduces carboxyl groups primarily in surface-exposed cryst.
Using time-resolved in situ at. Overall, this study reveals key characteristics of LPMO action on the cellulose surface and suggests the effects of substrate morphol. Enzymic conversion of polysaccharides into lower-mol. Polysaccharide monooxygenases PMOs use an oxidative mechanism to break the glycosidic bond of polymeric carbohydrates, thereby disrupting the cryst.
Reported here is a detailed anal. MS measurements. The cosubstrate utilized by the enzyme is dependent on the assay conditions. PMOs will directly reduce O2 in the coupled hydroxylation of substrate monooxygenase activity and will also utilize H2O2 peroxygenase activity produced from the uncoupled redn.
Both cosubstrates require Cu redn. Moreover, H2O2 does not influence the ability of secretome from Neurospora crassa to degrade Avicel, providing evidence that mol. ACS Catal. The discovery of lytic polysaccharide monooxygenases LPMOs has revolutionized enzymic processing of polysaccharides, in particular, recalcitrant insol. These monocopper enzymes display intriguing and unprecedented catalytic chem.
One issue of particular interest is the fact that both mol. Here, we review recent insights into the catalytic mechanism of LPMOs derived from structural, spectroscopic, and functional studies. We then turn to the question of how one can optimally harness the potential of LPMOs in biomass processing, given the current knowledge of their catalytic mechanism. Finally, we review recent, more applied studies that have addressed the importance of LPMOs in enzymic conversion of lignocellulosic biomass and discuss how the impact of these powerful enzymes could be improved.
Elsevier Ltd. Beta-glucosidase BGL is a rate-limiting enzyme for cellulose hydrolysis as it acts in the final step of lignocellulosic biomass conversion to convert cellobiose into glucose, the final end product. Most of the fungal strains used for cellulase prodn. Genetic engineering has enabled strain modification to produce BGL optimally with desired properties to be employed for biofuel applications.
It has been cloned either directly into the host strains lacking BGL or into another expression system, to be overexpressed to be blended into BGL deficient cellulases. In this article, role of genetic engineering to overcome BGL limitations in the cellulase cocktail and its significance for biofuel applications has been critically reviewed.
In the development of biofuel cells great effort is dedicated to achieving outstanding figures of merit, such as high stability, max.
Biofuel cells with immobilized redox mediators, such as redox polymers with integrated enzymes, show exptl. Although this phenomenon is widely reported in the literature, there is no comprehensive understanding of the potential shift, the high open circuit voltages have not been discussed in detail, and hence they are only accepted as an inherent property of the investigated systems.
We demonstrate that this effect is the result of a Nernstian shift of the electrode potential when catalytic conversion takes place in the absence or at very low current flow. Our findings have direct implications for the design and evaluation of bio fuel cells with pseudocapacitive elements.
Cellobiose Dehydrogenase: Bioelectrochemical Insights and Applications. Bioelectrochemistry , , , DOI: Elsevier B. Cellobiose dehydrogenase CDH is a flavocytochrome with a history of bioelectrochem. During the years, it has been shown to be capable of mediated electron transfer MET and direct electron transfer DET to a variety of electrodes.
This versatility of CDH originates from the sepn. This uncoupling of the catalytic reaction from the electron transfer process allows the application of CDH on many different electrode materials and surfaces, where it shows robust DET. Recent X-ray diffraction and small angle scattering studies provided insights into the structure of CDH and its domain mobility, which can change between a closed-state and an open-state conformation. This structural information verifies the electron transfer mechanism of CDH that was initially established by bioelectrochem.
Even more, electrochem. These electrochem. Heterologous Expression of Phanerochaete chrysosporium Cellobiose Dehydrogenase in Trichoderma reesei. Cell Factories , 20 , 2 , DOI: BioMed Central Ltd. The detd. Conclusions: Heterologous prodn. It also does not need a cellulose-based medium that impedes efficient prodn.
The obtained high uniformity of PcCDHTr glycoforms will be very useful to investigate electron transfer characteristics in biosensors and biofuel cells, which are depending on the spatial restrictions inflicted by high-mannose N-glycan trees.
Acta , , — , DOI: A review, with refs. Information from theor. The conclusion are sustained by examn. Biofuels , 13 , 37 , DOI: Although LPMOs receive ample interest in industry and academia, their reaction mechanism is not yet fully understood.
Recent studies showed that H2O2 is a more efficient cosubstrate for the enzyme than O2, which could greatly affect the utilization of LPMOs in industrial settings. The measurements were also followed by continuous electrochem. Different systems for the in situ generation of H2O2 and for the redn.
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