1,720,955 research outputs found
Capturing CO2 and N2 from the atmosphere: nitrogen-fixing cyanobacteria for sustainable industrial production of proteins
Get PDFThis PhD research project explores the potential of nitrogen-fixing cyanobacteria for sustainable and industrially relevant applications, with a focus on protein production and process optimization. Through an integrated approach combining experimental investigation, process modeling, and techno-economic analysis, this work aims to provide valuable insights into advancing bio-based solutions to global challenges such as food security, environmental sustainability, and resource efficiency. Continuous cultivation in flat panel photobioreactors of diazotrophic cyanobacteria, particularly Nostoc PCC 7120, is investigated as a strategy for stable protein production, with the potential of reducing the reliance on nitrogen fertilisers. Key operating variables are analysed to determine their effect on biomass productivity, quality, and nutritional value. Photorespirometry is employed to evaluate the physiological response of nitrogen-fixing cyanobacteria to light and temperature conditions. A Design of Experiments (DoE) framework is applied to systematically investigate and optimize cultivation conditions, focusing on the interplay between light and nutrient inputs to enhance productivity in high-density cultivation systems. Experimental findings contribute to the development of predictive kinetic models, including variables which are often overlooked like gas insufflation efficiency, establishing a basis for process optimization. The potential of Nostoc sp. as an iron-rich supplement is also investigated as an alternative application in nutraceuticals and functional foods by evaluating iron dynamics in both batch and continuous systems. Finally, based on the laboratory-scale results projected to a real plant scenario, a techno-economic analysis is performed on a one-hectare basis to assess the economic feasibility of the proposed process and explore alternative downstream possibilities
Optimization of Nostoc sp. biomass and protein composition in high-density cultivator based on DoE
No full textHigh-density (HD) cultivation systems are a valuable alternative to improve the productivity of phototrophic microorganisms. They are designed to address the major challenges such as low cell densities, light attenuation, and inefficient gas exchange, offering innovative solutions. This work investigates the HD cultivation of the nitrogen-fixing cyanobacterium Nostoc sp. PCC 7120 under diazotrophic conditions, employing a hydrophobic membrane system for efficient CO2 and N2 transfer. A design of experiment (DoE) approach is applied to evaluate the influence of key operating variables, including light intensity, photoperiod, and phosphorus concentration, on biomass productivity (PX) and nitrogen fixation (PN). Mathematical models, describing the interactions between these process variables and growth responses are developed and validated, enabling the optimization of cultivation conditions to maximise productivity. Remarkable biomass productivity of 1.53 gX L−1 d−1 was obtained in this system, under diazotrophic conditions. PX was largely affected by light intensity, which should be supplied continuously, aligning with the ability of heterocystous species like Nostoc sp. of simultaneously perform photosynthesis and N-fixation. Additionally, phosphorus concentration was a critical parameter that must be precisely controlled to prevent substrate limitation or inhibition, with an optimal value of 34.1 mgP L−1. The produced biomass was further characterised with a focus on its nitrogen-rich molecules, particularly proteins, and nutritional value, assessed through essential amino acid content. The results showed that protein content was improved (53.4 %) at 280 μmol m−2 s−1, 25.5 mgP L−1, and 18 h light period, with essential amino acid ranging between 11 % and 15 %
A Bioprocess Engineering Approach to Boost Selection of Fully Segregated Transformants in Cyanobacteria
Get PDFCyanobacteria are photoautotrophic microorganisms with significant applications in biotechnology. Although many cyanobacteria, including Picosynechococcus sp. (formerly called Synechococcus sp.) PCC 11901 (Picosynechococcus) and Synechocystis sp. PCC 6803 (Synechocystis), are readily and naturally transformable, their polyploidy poses a major challenge. To obtain a stable phenotype, transgenic strains must be fully segregated, i.e. mutations must appear in all chromosome copies. Traditional protocols rely on re-streaking of colonies on increasingly selective plates, a time-intensive laboratory procedure that requires continuous intervention from the operator. This study proposes an alternative protocol that combines transformation in a batch system in liquid culture with transformant selection in a continuous-flow stirred-tank reactor system. This protocol led to the successful selection of homoplasmic transformants of Picosynechococcus containing, alternatively, an antibiotic resistance alone (construct “SmR”) or a more complex construct (“bKT”) that leads to the accumulation of a ketocarotenoid. The stability of SmR transformants under semi-continuous cultivation in the absence of antibioticsf was tested for 42 days, proving their potential fitness to industrial cultivation conditions. The selection process was also validated on the model species Synechocystis, demonstrating its applicability to other cyanobacterial strains
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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