1,720,956 research outputs found
Diazotrophic Cyanobacteria for Protein Production: Hotorespirometry to Assess the Effect of Light and Temperature
No full textProtein production, thriving on the chemical fixation of nitrogen in fertilizers and intensive use of agricultural and livestock practices, significantly compromises environmental sustainability. The need for alternative food resources to meet the raised demand due to the fast-growing global population has turned pressing. Diazotrophic cyanobacteria, capable of converting atmospheric nitrogen into bioavailable forms, offer promise in sustainable protein production, bypassing traditional inefficiencies. Such microorganisms’ potential might be fully exploited if the production process is well-characterized and controlled. The primary objective of this study is to investigate the specific effects of light and temperature on the growth dynamics of Nostoc PCC 7120 by using photorespirometry. The study aims to retrieve kinetic parameters essential for predictive modeling in industrial applications. The optimal light intensity (376 μmol m-2 s-1) was estimated, as well as the optimal temperature. The latter showed to be dependent on culture conditions: under nitrogen-fixing conditions, it drops from 30 to 27 °C, highlighting temperature-driven effects based on the nitrogen source
Stabilizing autotrophic cyanophycin production in continuous photobioreactors
No full textCyanophycin, an intracellular reserve molecule synthetized by cyanobacteria, is considered as a potential biobased raw material for the industrial sector. It is usually produced through the cultivation of photosynthetic microorganisms in batch systems, which are affected by the high variability of cyanophycin accumulation due to varying growth phases, which lower the overall productivity. In this work, Synechocystis sp. PCC 6803 was cultivated in a continuous photobioreactor to increase cyanophycin productivity and to assess the feasibility of large-scale application. A stable production of the compound was obtained at steady-state. The effect of residence time and inlet phosphorus concentration on the biomass and cyanophycin productivity was evaluated, to identify the optimal conditions for its accumulation. A maximum value of cyanophycin productivity of about 30 mg L−1 d−1 was obtained, doubling the one achieved in the batch system. A quantitative correlation between the phosphorus quota and the cyanophycin produced was eventually proposed, highlighting a threshold of 4 mg of phosphorus per g of biomass for cyanophycin accumulation
Modeling Biomass Growth and Nitrogen Fixation by Heterocystous Cyanobacteria Cultivated in Continuous Photobioreactors
No full textNitrogen-fixing cyanobacteria application in bioprocesses holds the potential for enhanced bioindustry sustainability. To address challenges hindering microalgae-based processes scale-up, integrating empirical evidence with suitable kinetic models is crucial. Microalgae kinetic growth models usually disregard unique features of diazotrophic species, whose growth depends on both light intensity and dinitrogen availability. This work introduces a kinetic model separately describing vegetative cells and heterocyst growth, along with nitrogen accumulation in biomass, which was then validated on continuous cultivation data of two heterocystous species, namely, Anabaena and Nostoc. An experimental modeling-integrated approach was applied for species- and system-specific kinetic parameter retrieval. The lack of data on the effect of dissolved dinitrogen limitation in continuous systems was addressed by varying N2 partial pressures, demonstrating Nostoc promising N-fixation capabilities when N2 is not limiting compared to a combined nitrogen supply. The model accurately predicts how residence time, light, and nitrogen availability affect the growth of different species, encompassing both diazotrophic culture and combined nitrogen supply
From Nitrogen to Protein: Harnessing the Power of Nitrogen-Fixing Cyanobacteria for Protein-Rich Biomass Production
No full textTo meet the increasing demand for food and protein sources sustainably, innovative dietary alternatives must be explored. Nitrogen-fixing cyanobacteria represent a promising option for producing biomass with high nutritional value while promoting a more efficient and ecofriendly use of nitrogen resources. Most efforts still focus on optimizing the biomass and nutrient content, in terms of total protein, lipid, and carbohydrate composition. However, a systematic investigative approach to how the production system influences the nutritional value of biomass is still lacking. Crucial aspects, such as amino acid profile and bioaccessibility, are typically presented only as a final product characterization. This study presents the diazo-phototrophic continuous cultivation of the heterocystous cyanobacterium Nostoc PCC 7120 as a strategy for the stable production of protein-rich biomass without the need for a nitrogen fertilizer. Findings indicate that light intensity and residence time significantly affect the biomass nutritional value. Production under diazo-phototrophic conditions with a residence time of 1.07 +/- 0.11 days led to a notable increase in the essential amino acid content, which reached 15.06 +/- 0.35%. Considering also the conditionally indispensable amino acids for infant nutrition requirements-arginine, cysteine, and tyrosine-the percentage increased to 23.14 +/- 0.53%. Furthermore, protein bioaccessibility was measured at 81.3 +/- 3.6%, comparable to that of conventional vegetal protein sources like soy. In conclusion, continuous cultivation of Nostoc diazo-phototrophically presents a promising strategy for producing well-balanced biomass from a nutritional perspective, eliminating the need for an external nitrogen fertilizer
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
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