1,720,960 research outputs found
Innovative biotechnological process for the conversion of lignocellulosic biomasses into high added-value products.
No full textClimate change and environment degradation are an concrete threats for the world. To overcome these threats, the European Union (EU) has put in place the European Green Deal (EGD), a growth strategy aimed at developing an EU competitive and sustainable economy. The EGD, adopted at the end of 2019, provides the action plan to achieve the carbon neutrality, resource efficiency and zero pollution in the EU by 2050. This set of policy initiatives, coupled with the new EU Recovery Plan developed to support the repair of the economic and social damages caused by the COVID-19 pandemic, represents today the most crucial milestones in the green transition towards a more resilient, competitive and environmentally sustainable Europe. The transition from a fossil-based economy to a bio-based economy is necessary to guarantee a sustainable future for the society. In this sense, the development of biorefinery processes able to replace traditional fossil processes has attracted great attention. Biorefineries are technological platforms making use of both biotechnological and/or chemical processes to convert different bioresources into a spectrum of high value-added products. One of the most widespread and consolidated biomass biorefinery processes concerns the production of first-generation biofuels from vegetable oils, but the environmental externalities due to the intensive cultivation of oil crops has led several European countries to discourage the use of some vegetable oils for biofuels production. An excellent, green, and sustainable alternative to vegetable oils is represented by microbial oils produced by oleaginous microorganisms.
Some microorganisms are defined oleaginous in consequence of their ability to accumulate lipids for over 20% of their dry cellular weight. This group includes several eukaryotic microorganisms (such as fungi, yeasts and algae) and some species of autotrophic and heterotrophic bacteria able to accumulate lipids in the form of triglyceride (TAG). Among these, the yeasts are considered the best candidates for industrial processes thanks to their rapid growth, the ability to utilize a wide variety of raw materials and the easy cultivation in large fermenters. The lipids produced by oleaginous yeasts, better known as Single Cell Oil (SCOs), have a composition very similar to vegetable oils, with a predominance of oleic acid (18:1), followed by palmitic acid (C16:0), linoleic acid (C18:2), and stearic acid (C18:0). Of the 1500 known species belonging to 100 different genera, about 30 of them are capable of accumulating lipids, and the most known oleaginous yeasts include the genera Yarrowia, Rhodotorula (Rhodosporidium), Lipomyces, and Cryptococcus. SCOs may serve as a renewable source of edible oil and as an intermediate ‘‘building block’’ for oleochemicals, including: fuels, soaps, plastics, paints, detergents, textiles, rubber, surfactants, lubricants, additives for the food and cosmetic industry and many other chemicals.
Although the use of SCOs as a feedstock for biofuels and biochemicals has received interest in recent years, high production costs, estimated in the range 4.1 and 5.8 $ / kg, prevented their industrial applications. Using low-cost carbon sources together with more efficient bioconversion processes could make this process more competitive.
Several types of waste and low-cost carbon sources, including olive mill wastewater, and by-products of the dairy industry, food processing, and lignocellulosic residues have been used as feedstock to produce microbial lipids. Due to the high content of inorganic material, widely available lignocellulosic residues such as agricultural straws could be more suitable to achieve fermentable sugars with respect to produce heat and electricity through thermal processes. Due to their recalcitrant nature, lignocellulosic biomasses require pre-treatments to favour the breakdown of the lignin structural matrix and favour the enzymatic hydrolysis of polysaccharides. Pre-treatment involves the application of physical, chemical, biological or physicochemical approaches, among which steam explosion has been recognized as one of the most effective, economical and sustainable processes. The main limit of this technology is the formation of thermal degradation by-products, such as 5-hydroxymethylfurfural (5-HMF), furfural, weak acids, and phenols. These molecules could inhibit the growth of most microorganisms. For these reasons scientific efforts are aimed at identifying robust microorganisms able of tolerating the stress induced by these molecules. In addition, genetic engineering, adaptive evolutionary techniques, and fermentation strategies could improve the specific microorganism resistance and increase the process yields.
This PhD was supported by regional government in the framework of the industry 4.0 strategy and, in order to meet the needs of the Basilicata region, the main objective of this PhD activity was the development of a process which might be useful for regional economy. By considering the strong agricultural vocation of Basilicata region and the presence in this area of one of the largest oil fields in Europe, this PhD project was aimed to develop a biorefinery process for valorisation of agricultural wastes, for the production of high added-value products. The development of a biorefinery process useful for enhancing the local agriculture by-products represents a green and sustainable alternative to classic petrochemical processes.
The aim of this Ph.D. thesis was the investigation and the optimization of innovative processes to convert lignocellulosic residues into microbial oils at industrial relevant conditions. In fact the profitable conversion of lignocellulosic biomass into biobased products through the platform sugars requires the intermediate production of concentrated biomass hydrolysates that, however, could contain many microbial inhibitors. The development of optimized bioconversions processes could alleviate the production costs for the hydrolysates detoxification. In particular, the research work concerned the conversion of second-generation sugars through previously optimized processes of steam pretreatment and enzymatic hydrolysis of wheat straw and cardoon residues into microbial oils. Teste microorganisms included oleaginous yeasts belonging to the species Cutaneotrichosporon curvatus CA-3802, Lipomyces tetrasporus Li-0407, and Yarrowia lipolytica ATCC 46483. Many fermentation set-up were developed to overcome the inhibition induced by thermal degradation by-products and maximize the conversion yields. The fermentation process optimized in shaken flasks was then scaled-up in the 2, 10 and 50 L stirred tank bioreactor. According to sustainable chemistry strategies and to improve the economic feasibility of the process, the downstream phase was implemented through the use of sustainable and non-hazardous solvents. Furthermore, the suitability of the microbial oil versus target applications was investigated for the production of biodiesel, green diesel and polyurethanes. Finally, on the basis of the biorefinery process developed in this Ph.D. thesis, a technical-economic analysis was carried out.
Specific aims of the research project were the following:
I. To study and optimize the growth of oleaginous yeasts in simulated medium and un-detoxified biomass hydrolysates, and improvement of the microbial conversion in order to produce high-titer lipids;
II. scale-up of the biorefinery process from laboratory to pilot scale;
III. evaluate an innovative extraction mixture and synthesize high added-value products, such as intermediates for the food and oleochemical industries;
IV. to evaluate the overall economic feasibility of the implemented process through a technical-economic analysis;
In particular, Chapter I describes the state of the art of the proposed process with particular interest on the use of oleaginous yeasts for the production of SCOs.
Chapters II and III describe the microbial conversion of undetoxified lignocellulosic hydrolysates, such as cardoon residues hydrolysate and wheat straw hydrolysate, by the use of Cutaneotrichosporon curvatus CA-3802, Lipomyces tetrasporus Li-0407, and Yarrowia lipolytica ATCC 46483. The activities were focused on the process conditions useful to overcome the inhibition induced by the biomass degradation products. Furthermore, the microbial lipids obtained were characterized and converted into high added-value products.
Chapter IV describe the implementation of economic feasibility and scale-up of the process. The first step was addressed to the optimization of enzymatic hydrolysis process of steam pretreated wheat straw in order to enhance economic feasibility of the process through the decrease of the enzymatic load. Subsequently, cheap nitrogen sources were also evaluated in the lipid synthesis phase. The scale-up of the process was carried out in pilot scale 50 L bioreactor.
Lipids extraction and synthesis of high added-value products were described in Chapter V. An innovative extraction solvent was studied. Microbial lipids produced were converted into advanced fuels for hydrocarbon industry and microbial bioplastics.
Finally, the technical-economic analysis of the proposed biorefinery process was described in Chapter VI
Techno-economic Analysis of a Lignocellulosic Biorefinery Producing Microbial Oils by Oleaginous Yeasts
No full textThe lignocellulosic biomass valorisation is a central challenge of the bioeconomy transition, which passes through optimization of the entire value chain, from feedstock availability, sustainable conversion processes, to final target products. In this framework, the oleaginous yeasts represent a versatile tool to produce biobased chemicals and intermediates. They are flexible microbial factories able to grow on different side-stream carbon sources such as those deriving from lignocellulosic biomass, and this characteristic makes them excellent candidates for integrated biorefinery processes through the production of microbial lipids/oils. This work aims at a techno-economic analysis of a lignocellulosic biorefinery producing microbial oils by oleaginous yeasts (Lipomyces tetrasporus). The wheat straw residues were considered as the lignocellulosic feedstock thanks to a huge amount in the European territory. Experimental data obtained by a complete lab-scale 2G-sugars platform (steam explosion pretreatment, enzymatic hydrolysis, fermentation) were used for the analysis until microbic growth. Commercial/literature data were considered for the lipids extraction and purification stages. An assessment of the mass and energy balances, equipment sizing, costs estimation was carried out with the main results showing a production cost of the microbial oil about 4 €/kg with the enzymes supply as the major cost contribution
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
Catalytic and biocatalytic cascade conversion of giant reed and cardoon residues to glucose, levulinic acid, and long-chain fatty acid methyl esters
No full textGiant reed was hydrolysed by the green salt FeCl3 under microwave irradiation. Differently, cardoon residues were pretreated by steam explosion and hydrolysed by the same catalyst. Each pretreatment showed efficient biomass fractionation, with xylan hydrolysis reaching 99 mol% for giant reed and 70 mol% for cardoon. Then, glucose yields of 55 and 30 mol% were obtained for giant reed and cardoon, respectively, under mild reaction conditions (34 min, 150 °C, biomass loading 9 wt%, FeCl3 2.7 wt%). Sugars-rich hydrolysates were fermented by the yeasts L. starkeyi and L. tetrasporus to produce triglycerides. L. starkeyi achieved a lipid yield of 13.5 wt% from giant reed hydrolysate and 14.2 wt% from cardoon hydrolysate. L. tetrasporus reached a lipid yield of 16.0 and 17.6 wt% from giant reed and cardoon hydrolysate, respectively. Moreover, both yeasts were able to convert cardoon hemicellulose into triglycerides, reaching at pH 5.5 a lipid yield of 13.9 wt% (L. starkeyi) and 19.4 wt% (L. tetrasporus). These oils were converted to long-chain fatty acids methyl esters. The final valorisation of unconverted glucan in solid residues resulted in the FeCl3-catalysed production of levulinic acid and formic acid to close the biorefinery cycle of both biomasses
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
- …
