1,720,956 research outputs found
Expression and biochemical characterization of maltogenic amylase from bacillus lehensis G1
Full text linkThis study was carried out for the expression and characterization of maltogenic amylase (MAG1) from Bacillus lehensis G1. Amplification of 1741 base pair gene fragments encoding MAG1 and expression in Escherichia coli have been successful. The expression of MAG1 was optimized at 30°C and 0.5 mM isopropyl ß-D-1-thiogalactopyranoside (IPTG) for a period of 12 hour post-induction time. Purification of the crude enzyme was done using the ACTAprime System which uses the concept of affinity chromatography. The optimum temperature and pH of the purified MAG1 were 40 °C and pH 7.0 respectively. The enzyme did not show potent thermostability and was stable at pH ranging from 7.0 to 9.0. The purified MAG1 has a preference towards cyclodextrin (CD) specifically ß-CD. Starches were least favored by MAG1 followed by pullulan. Only the metal ion Mn2+ increased the activity of MAG1 while K2+, Li2+ and Mg2+ slightly affect its activity. The metal ion Ca2+ significantly reduced MAG1 activity while Fe2+, Co2+, Zn2+, Cu2+, Pb2+ and Ni2+ drastically reduced the activity of MAG1. In terms of additives, only 2- mercaptoethanol (2-ME) managed to enhance the activity of MAG1 while ethylenediaminetetraacetic acid (EDTA) and Tween20 did not affect its activity. Drastic reduction of MAG1 activity was caused by phenylmethylsulfonyl fluoride (PMSF), sodium dodecyl sulfate (SDS), methanol and ethanol. The hydrolysis pattern of MAG1 was studied using CDs and maltooligosaccharides. The hydrolysis of CDs resulted in the formation of maltose but no glucose was detected. MAG1 was also able to linearize the CDs. MAG1 did not react with glucose, maltose and maltotriose but did react with maltotetraose, maltopentaose, maltohexaose and maltoheptaose to produce mainly maltose and maltotriose. The Km and Vmax of MAG1 towards ß-CD were 6.358 mg/mL and 91.63 µmol/min respectivel
Enhancing the immobilization of cyclodextrin glucanotransferase producing escherichia coli for direct conversion of starch to ß-cyclodextrin
Full text linkEnzyme can be considered as one of the most used and effective biocatalyst both in research and industry. However, some of the major drawbacks of using enzyme are their cost and the unavoidable one-time-usage. This problem has been temporary solved by enzyme immobilization. Nevertheless, there are still disadvantages especially in terms of the enzyme stability and reduction of catalytic activity. Therefore, whole-cell immobilization, also known as whole-cell biocatalyst, can provide a better solution as the immobilized whole-cell can provide fresh enzyme for each reaction and has high reusability. In this study, Escherichia coli (E. coli) harbouring the enzyme cyclodextrin glucanotransferase (CGTase) was immobilized to a commercial activated charcoal (ACh) for the direct conversion of starch to ß-cyclodextrin (ß-CD). The immobilization of the E. coli was enhanced by employing two methods; first, treatment to the ACh, and second, manipulating the appendages of the E. coli called curli. This is done because cell immobilization can become problematic in terms of the amount of cell successfully immobilized. The treatment of the ACh was done through chemical treatment, using four different chemicals, sodium hydroxide (NaOH), hydrochloric acid (HCl), ammonium hydroxide (NH4OH), and acetic acid (CH3COOH). The treatment was done relatively at mild conditions. Treatment with NaOH showed the highest increment in cell immobilized with more than 120 % increase. This is mainly attributed by the higher surface area and pore volume resulted from the NaOH treatment. The manipulation of the curli was done by the addition of nickel (II) chloride during the immobilization process. The added nickel triggered the natural response of the cell, forcing the cell to produce its curli and making the cell sticky and easily attached to surfaces. This in turn further increased the cell immobilized by at least 50 %. The resulting enhanced-immobilized cell increases CGTase activity by 10 % and can be reused up to 10 cycles for CGTase expression and showed lower cell lysis compare to both the free cell and to the cell immobilized without any treatment. The optimization of starch direct conversion using the immobilized cell was done using the Box-Behnken design in the design expert software. Under the optimized condition, the highest yield of 15.45 mg/mL ß-CD was obtained, which was analysed using high performance liquid chromatography, and the immobilized cell was managed to be reused up to 6 cycles. Based on the results of this study, it can be concluded that the immobilization of E. coli was greatly enhanced by the combination of the two methods, ACh treatment and curli manipulation. Also, the enhancement resulted in less cell lysis and stronger cell attachment to the support material. The immobilized cell was successful in directly converting starch to ß-CD
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
Full text link“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
Full text linkWe 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
Full text linkWe 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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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