1,720,968 research outputs found
Innovative of second generation ethanol production from biomass crops by pichia stipitis
No full textThe production of ethanol from lignocellulosic material, as reported by Kumar (2009), consists of mainly five different steps, namely pretreatment, (enzymatic) hydrolysis, fermentation, product separation and post-treatment of the liquid fraction. The pretreatment is necessary to improve the rate of production and the total yield of monomeric sugars in the hydrolysis step. The produced monomeric hexoses (six carbon sugars) can be fermented to ethanol quite easily, while the fermentation of pentoses (five carbon sugars) is only made by a few strains. It's been choosen a strain of Pichia stipitis wich is able to convert hexoses and pentoses to ethanol. Preliminary tests with P. stipitis and synthetic broth containing glucose and xylose confirmed the utility of P. stipitis to produce ethanol by hexoses and pentoses.. Pretreatment (acid and alkali), hydrolysis with enzymes and fermentation with P. stipitis allowed to produce ethanol by using mulberry as biomass. © 2014, AIDIC Servizi S.r.l
Bioethanol and biomethane potential production of thirteen pluri-annual herbaceous species
No full textThe research aimed to study and characterize, in a four-year study, thirteen pluri-annual herbaceous species for their potential bioethanol and biomethane production. The highest biomass yield was obtained with Arundo donax followed by Miscanthus x giganteus. Biomass cellulose content had median values ranging from 23.1% (Symphytum x uplandicum) to 45.4% (Lythrum salicaria), hemicellulose from 9.4% (Iris pseudacorus) to 36.8% (Glyceria maxima) and lignin from 2.6% (G. maxima) to 14.5% (Helianthus tuberosus and L. salicaria). The best ethanol and methane median yields were achieved by A. donax (3.5 Mg ha−1 and 8227 m3 ha−1, respectively) followed by M. x giganteus (3.2 Mg ha−1 and 4446 m3 ha−1, respectively). Methane transformation showed a higher energy output than ethanol with values ranging from 1 GJ ha−1 (Phalaris arundinacea) to 508 GJ ha−1 (A. donax) and from 1 GJ ha−1 (P. arundinacea) to 624 GJ ha−1 (A. donax) for ethanol and methane, respectively. Results showed that A. donax and M. x giganteus are the most interesting species for bioethanol and biomethane production. © 2018 Elsevier B.V
Conversion of crude glycerol to citric acid by yarrowia lipolytica
No full textCitric acid is a key biochemical in the emerging bioeconomy, to date mostly produced through fermentation by A. niger of molasses. One main issue is represented by the replacement of the molasses-based medium with less expensive and more sustainable feedstocks. Crude glycerol, a secondary product from the biodiesel industry was used without any pretreatment as substrate for fermentation by Yarrowia lipolytica DSM 8218 to produce it. The raw glycerol was retrieved from a local biodiesel production plant. The fermentation set-up was first optimized in flasks by using the Response Surface Methodology (RSM). A 3-level Full Factorial Design of Experiment was employed to investigate the impact of crude glycerol concentration and C/N ratio on citric acid yield and two N sources (ammonium sulphate and yeast extract) were alternatively tested. The optimized conditions were subsequently applied to a 2L bioreactor. The best conditions to maximize YCA were found to be: crude glycerol 33 g/L and C/N 141, which resulted in the production of 8 g/L of citric acid and in a metabolic yield of 0,27 g/g. Scale up in bioreactor indicated that the citric acid production like can be controlled and improved by adjusting the concentration of dissolved oxygen
Conversion of raw glycerol and cardoon hydrolysate into single cell oil by oleaginous yeasts
No full textThe interest in the bio-based products, namely biofuels and chemicals, has increased in recent years often driven by global concerns about the depletion of the fossil resources and environmental implications. The biomass residues and waste streams from several origins could represent sustainable feedstocks to produce both bioenergy and bio-based products. Microbial oils can be used in a number of oil-based processes, including biodiesel, lubricants, bioplastics production. Their economic feasibility depends on the growing substrates. In order to achieve a feasible production of microbial bio-oils, low-cost substrates are necessary. Aim of the present work was the conversion of un-detoxified hydrolysates of cardoon and raw glycerol from the biodiesel production by Cryptococcus curvatus to develop a cost–effective microbial production of oils. The growth and the lipid production of the oleaginous yeast was assessed at different C/N in batch cultures. The lipids accumulation during the process was monitored through the Nile Red spectrofluorometric analyses. Composition of raw glycerol resulted more inhibitory than cardoon hydrolysate so that no yeast growth was observed above the C/N ratio threshold of 65. The maximum C. curvatus lipid content were 67.2% and 43.7% (g lipids/g cell dry biomass produced %) on cardoon hydrolysate and raw glycerol respectively. The FAME profiles revealed the predominance of fatty acids, namely palmitic, stearic, oleic and linoleic acid, in different percentages depending on the carbon source and on the carbon-to-nitrogen ratios used. The data indicated that the fatty acid compositions depends not only on the C/N ratio but also on the specific carbon source leading to different features and potential applications for the industrial production of renewable chemicals
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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