1,720,957 research outputs found
Genetic engineering of Nannochloropsis oceanica to produce canthaxanthin and ketocarotenoids
Full text linkBackground
Canthaxanthin is a ketocarotenoid with high antioxidant activity, and it is primarily produced by microalgae, among which Nannochloropsis oceanica, a marine alga widely used for aquaculture. In the last decade, N. oceanica has become a model organism for oleaginous microalgae to develop sustainable processes to produce biomolecules of interest by exploiting its photosynthetic activity and carbon assimilation properties. N. oceanica can accumulate lipids up to 70% of total dry weight and contains the omega-3 fatty acid eicosapentaenoic acid (EPA) required for both food and feed applications. The genome sequence, other omics data, and synthetic biology tools are available for this species, including an engineered strain called LP-tdTomato, which allows homologous recombination to insert the heterologous genes in a highly transcribed locus in the nucleolus region. Here, N. oceanica was engineered to induce high ketocarotenoid and canthaxanthin production.
Results
We used N. oceanica LP-tdTomato strain as a background to express the key enzyme for ketocarotenoid production, a β-carotene ketolase (CrBKT) from Chlamydomonas reinhardtii. Through the LP-tdTomato strain, the transgene insertion by homologous recombination in a highly transcribed genomic locus can be screened by negative fluorescence. The overexpression of CrBKT in bkt transformants increased the content of carotenoids and ketocarotenoids per cell, respectively, 1.5 and 10-fold, inducing an orange/red color in the bkt cell cultures. Background (LP) and bkt lines productivity were compared at different light intensities from 150 to 1200 μmol m-2 s-1: at lower irradiances, the growth kinetics of bkt lines were slower compared to LP, while higher productivity was measured for bkt lines at 1200 μmol m-2 s-1. Despite these results, the highest canthaxanthin and ketocarotenoids productivity were obtained upon cultivation at 150 μmol m-2 s-1.
Conclusions
Through targeted gene redesign and heterologous transformation, ketocarotenoids and canthaxanthin content were significantly increased, achieving 0.3% and 0.2% dry weight. Canthaxanthin could be produced using CO2 as the only carbon source at 1.5 mg/L titer. These bkt-engineered lines hold potential for industrial applications in fish or poultry feed sectors, where canthaxanthin and ketocarotenoids are required as pigmentation agents
Mixotrophic and Heterotrophic Metabolism in Brewery Wastewater by Chlorella Vulgaris: Effect on Growth, FAME Profile, and Biodiesel Properties
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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
Dairy Wastewater to Promote Mixotrophic and Heterotrophic Metabolism in Chlorella Vulgaris: Effect on Growth and FAME Profile
Full text linkThe increase of greenhouse gases into the atmosphere represents today one of the most global concern. The inevitable depletion of fossil fuels and the adverse climate changes push the scientific community to seek renewable and sustainable sources of fuel. In this scenario microalgae can be potentially exploited as renewable and environmentally friendly fuel resources. Wastewaters (WW) can be used as culture media reducing the costs associated to their cultivation. Hence, the goal of this study was to examine the effect of an organic rich WW on Chlorella vulgaris growth and fatty acid methyl esters (FAME) profile. This strain shows high biomass productivity thriving in a wide range of WWs and is able to shift its metabolism from autotrophic to hetero/mixotrophic one. Glycerol can be used to convey metabolism towards lipids production. Therefore, C. vulgaris was cultivated in dairy waste (DWW) with different concentrations of glycerol under both metabolisms. When C. vulgaris was cultivated under mixotrophy attained a high biomass yield compared to heterotrophy. The highest biomass yield (1.72 g L-1) was obtained with 10 mL of glycerol in DWW compared to the control (1.08 g L-1). When a two-phase metabolism was adopted, that is the first ten days under mixotrophy followed by the last five days in heterotrophy (MHD), the biomass was almost doubled with 2 mL of glycerol in DWW. FAME profile reveled that compared to the control the highest saturated fatty acids (SFA), monounsaturated fatty acids (MUFA), and polyunsaturated fatty acids (PUFA) content were obtained under heterotrophy with 10 mL of glycerol, under MHD with 2 mL and with 4 mL of glycerol (46.73%wt, 41.79%wt, and 30.34%wt, respectively). A preliminary analysis on the saturated and unsaturated components of the FAME suggests that lipids extracted from C. vulgaris biomass cultivated mixotrophically and heterorophically in DWW could represents a feedstock to be exploited for biodiesel production
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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