1,720,973 research outputs found
Influence of various fermentation variables on exo-glucanase production in Cellulomonas flavigena
Get PDFThe influence of carbon and nitrogen sources on the production of exo-glucanase was investigated. The enzyme production was variable according to the carbon or nitrogen source used. Levels of b-cellobiohydrolase (CBH) were minimal in the presence of even low concentrations of glucose. Enzyme production was stimulated by other carbohydrates and thus is subject to carbon source control by easily metabolizable sugars. In Dubos medium, on cellobiose, the cellobiohydrolase titres were 2-to 110-fold higher with cells growing on monomeric sugars and 2.7 times higher than cells growing on other disaccharides. a-Cellulose was the most effective inducer of b-cellobiohydrlase and filter paperase (FPase) activities, followed by kallar grass straw. Exogenously supplied glucose inhibited the synthesis of the enzyme in cultures of Cellulomonas flavigena. Nitrates were the best nitrogen sources and supported greater cell mass, cellobiohydrolase and FPase production. During growth on a-cellulose containing 8-fold sodium nitrate concentration, maximum volumetric productivities (Qp) of b-cellobiohydrolase and FPase were 87.5 and 79.5 IU/l./h respectively and are significantly higher than the values reported for some other potent fungi and bacteria
Hyper-production of a thermotolerant β-xylosidase by a deoxy-D-glucose and cycloheximide resistant mutant derivative of Kluyveromyces marxianus PPY 125
No full textProduction of β-xylosidaseby a cycloheximide and
2-deoxy-D-glucose-resistant mutant of Kluyveromyces marxianus
PPY125 was studied when cultured on growth media containing galactose,
glucose, xylose, cellobiose, sucrose and lactose as carbon sources.
Xylose, cellobiose, lactose and sucrose were the key substrates. Both
K. marxianus PPY125 and its mutant (M 125) supported maximum
β-xylosidase specific product yield (YP/X) following growth on
xylose. Basal level of activity was observed in non-induced cultures
grown on glucose. The mutant produced 1.5 to 2-fold more
β-xylosidase than that produced by the wild cells. Synthesis of
β-xylosidase was regulated by an induction mechanism in both wild
and mutant cells. Addition of glucose did not inhibit the synthesis of
β-xylosidase in both parental and mutant cultures in the presence
of corn steep liquor. Partially purified enzyme showed good stability
when incubated at 60°C and was quite stable at pH 5.0-7.0.
Thermodynamic studies revealed that the enzyme derived by the mutant
M125 was more thermostable as evidenced by higher midpoint inactivation
temperature, lower activation energy demand for β-xyloside
hydrolysis, as well as lower enthalpy and entropy demand for reversible
denaturation of enzyme
Hyper-production of a thermotolerant β-xylosidase by a deoxy-D-glucose and cycloheximide resistant mutant derivative of Kluyveromyces marxianus PPY 125
No full textProduction of β-xylosidaseby a cycloheximide and
2-deoxy-D-glucose-resistant mutant of Kluyveromyces marxianus
PPY125 was studied when cultured on growth media containing galactose,
glucose, xylose, cellobiose, sucrose and lactose as carbon sources.
Xylose, cellobiose, lactose and sucrose were the key substrates. Both
K. marxianus PPY125 and its mutant (M 125) supported maximum
β-xylosidase specific product yield (YP/X) following growth on
xylose. Basal level of activity was observed in non-induced cultures
grown on glucose. The mutant produced 1.5 to 2-fold more
β-xylosidase than that produced by the wild cells. Synthesis of
β-xylosidase was regulated by an induction mechanism in both wild
and mutant cells. Addition of glucose did not inhibit the synthesis of
β-xylosidase in both parental and mutant cultures in the presence
of corn steep liquor. Partially purified enzyme showed good stability
when incubated at 60°C and was quite stable at pH 5.0-7.0.
Thermodynamic studies revealed that the enzyme derived by the mutant
M125 was more thermostable as evidenced by higher midpoint inactivation
temperature, lower activation energy demand for β-xyloside
hydrolysis, as well as lower enthalpy and entropy demand for reversible
denaturation of enzyme
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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