1,720,999 research outputs found
Study of Lipase Production by Yarrowia Lipolytica Grown in High Concentration of Hydrophobic Carbon Sources
No full textYarrowia lipolytica is one of the most studied “non-conventional” oleaginous yeasts. It is able to produce a number of valuable proteins and metabolites such as lipases and other hydrolytic enzymes, single cell oils (SCOs), single cell proteins (SCPs), carboxylic acids, erythritol and γ-decalactone (Nicaud, 2012). Scientific research is focusing on Y. lipolytica due to its ability to grow on different carbon sources, both hydrophobic and hydrophilic, and to its high tolerance to broad pH ranges and salt concentrations (Miller and Halper, 2019). Lipases (EC 3.1.1.3) are a class of hydrolases which naturally catalyze the hydrolysis of triglycerides to glycerol and free fatty acids at the oil–water interface in the presence of emulsions. Furthermore, lipases are very important for the synthesis of esters through esterification and transesterification reactions in anhydrous conditions, with high enantioselectivity. For their ability to catalyze specific biotransformations in different reaction media, lipases have been employed in several industrial sectors, from the pharmaceutical to food and chemical industries (Treichel et al., 2010). Y. lipolytica use as a sustainable platform for lipase production has been investigate using waste cooking oils (WCOs). The term WCO refers to oils and fats from food processing and storage at a commercial, industrial or household level. In Europe, WCOs annual production accounts for approximately 4 million tons/y (EBIA, 2021). If not collected and properly disposed of, WCOs can form the so-called “fatbergs” that can damage and clog the sewage system and pollute water and soil (Foo et al., 2014). In this work, the capabilities of Y. lipolytica to grow on high concentrations of different hydrophobic carbon sources, such as Olive Oil and WCOs, among others, were investigated to evaluate their potential as inducers for lipase production
Physiological Characterisation of Yarrowia lipolytica Cultures Grown on Alternative Carbon Sources to Develop Microbial Platforms for Waste Cooking Oils Valorisation
No full textWith the economic development, the non-renewable resources consumption and the energy crisis, microbial-based platforms represent a promising alternative route for the production of valuable chemicals. Yarrowia lipolytica is a non-conventional oleaginous yeast, which is able to grow on hydrophobic substrates, such as triglycerides, as carbon source. Its growth is associated with the production of different high-value bio-products, such as enzymes, organic acids, and lipids. In recent years, both basic and applied research have been carried out for improving its genetic manipulation and industrial use. The thorough knowledge of Y. lipolytica biolipid conversion and production pathways makes it a good candidate for its use as a cell factory for the design of alternative bioprocesses based on renewable substrates. Waste cooking oils (WCOs) are vegetable oils and animal fats that are discarded after food processing. Globally, high amounts of this waste product are produced every year. Due to their composition in triglycerides, WCO can be used as feedstock for microbial growth to create novel routes for the so-called “industrial symbiosis” following the circular economy approach, to upgrade a waste as a renewable feedstock for the bio-based industry. In particular, the goal of this study was the creation of new value chains from waste cooking oil (WCO) for the sustainable production of added-value compounds to valorize this type of waste and to reduce its incorrect disposal. Specifically, Y. lipolytica was investigated to evaluate its ability to grow in the presence of different concentrations of WCO compared to glucose as carbon source and determine its response both in terms of industrially-relevant compounds production and cell robustness. Flow cytometry analysis was performed to investigate the response of Y. lipolytica at increasing WCO concentrations in terms of intracellular lipids quantification and cellular viability
Metabolite transport and its impact on metabolic engineering approaches
Full text linkCells are the structural units of life and are separated from the environment by at least one cellular membrane consisting of a lipid bilayer. Thus, metabolite transport across cellular membranes is a key feature of living organisms. Specialized proteins or protein complexes mediate transport processes and are accessible to metabolic engineering approaches. Genetic modifications in metabolic engineering has mostly involved the deletion or overexpression of genes encoding for enzymes. The role of transporters has received much less attention, but as this special issue shows, it is a key factor to consider when rationally designing microbial cell factories. Transporters have been employed in metabolic engineering endeavors to target three fundamental aspects: Import of substrates , Export of products , Modification of intracellular fluxes
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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