The influence of metal crystallite size of the cobalt Fischer-Tropsch catalyst on the re-oxidation of cobalt with water

Bibliography: leaves 127-134.Catalyst productivity and selectivity to C5+ hydrocarbons are an important criteria in choice of Fischer-Tropsch catalyst. Cobalt-based catalysts appear to provide the best compromise between performance and cost for the synthesis of hydrocarbons [Iglesia, 1997]. The cobalt-based catalysts can be best applied in slurry reactor technology because of the high activity and the good heat transfer of the slurry reactor. Due to the nature of the slurry reactor, high partial pressures of water are generated when operated at high conversions. In addition, the back-mixing in the slurry reactors gives a homogenous concentration profile throughout the reactor with high water and low reactants concentrations. The cobalt catalyst is more expensive than the iron catalyst and to make the cobalt catalyst economically viable, the lifetime of the catalyst has to be stretched to 2-3 years. Possible deactivation by water thus becomes of major concern. Although the deactivation of bulk cobalt with water is not thermodynamically feasible, the re-oxidation of the metal surface might be possible. The surface atoms of a solid are exposed to a different environment than the atoms in the bulk of the solid. They have fewer neighbours than the bulk atoms do. The neighbours of each surface atom may be distributed anisotropically. Therefore the thermodynamic properties associated with the surface region are defined separately from the bulk thermodynamic properties. Studies of small particles have shown that these exhibit properties different from those of the bulk phase especially when dispersion approaches unity [Somorjai, 1994]. Significant surface oxidation is found when the Co/Al2O3 is treated with low H2O/H2 ratio [Schanke et. al. 1996]. In the present study the role of the cobalt crystallite size on the re-oxidation of a 5%(wt) Co/SiO2 catalyst has been investigated with TPR, TPO, H2 chemisorption, TEM and Fischer-Tropsch synthesis. The supported catalysts used in this study were prepared by impregnating a silica support with an aqueous solution of cobalt nitrate, using the incipient wetness technique. Impregnation was followed by drying and activation of the cobalt precursor

Characterization and engineering of Bacillus megaterium AS-35, for use in biodegradation of processed olive wastewater

Philosophiae Doctor - PhDThe popularization and health benefits associated with the "Mediterranean diet" saw a world wide increase in the production and consumption of processed olives and olive oil. During the brining of table olives large quantities of processed olive waste water is seasonally generated. This blackish-brown, malodours liquid is rich in organic and phenolic compounds, which cause environmental problems upon discarding. Currently, processed wastewater is discarded into large evaporation ponds where it poses serious environmental risks. The biodegradation of organic substrates present in the olive wastewater is inhibited by the high concentrations of phenolic compounds

Characterization of a putative pilus assembly and secretion system in Pseudomonas aeruginosa DSM 1707

Please read the abstract in the section 00front of this documentDissertation (MSc (Microbiology))--University of Pretoria, 2005.Microbiology and Plant Pathologyunrestricte

Post-genomic era in agriculture and veterinary science: successful and proposed application of genetic targeting technologies

Gene editing tools have become an indispensable part of research into the fundamental aspects of cell biology. With a vast body of literature having been generated based on next generation sequencing technologies, keeping track of this ever-growing body of information remains challenging. This necessitates the translation of genomic data into tangible applications. In order to address this objective, the generated Next Generation Sequencing (NGS) data forms the basis for targeted genome editing strategies, employing known enzymes of various cellular machinery, in generating organisms with specifically selected phenotypes. This review focuses primarily on CRISPR/Cas9 technology in the context of its advantages over Zinc finger proteins (ZNF) and Transcription activator-like effector nucleases (TALEN) and meganucleases mutagenesis strategies, for use in agricultural and veterinary applications. This review will describe the application of CRISPR/Cas9 in creating modified organisms with custom-made properties, without the undesired non-targeted effects associated with virus vector vaccines and bioactive molecules produced in bacterial systems. Examples of the successful and unsuccessful applications of this technology to plants, animals and microorganisms are provided, as well as an in-depth look into possible future trends and applications in vaccine development, disease resistance and enhanced phenotypic traits will be discussed

Whole-genome sequencing of African swine fever virus from wild boars in the Kaliningrad region reveals unique and distinguishing genomic mutations

Since the first report of outbreaks of African swine fever (ASF) in Georgia in 2007, the disease has expanded into Europe, Russia, and Asia, spreading rapidly via contact with infected animals including domestic pigs and wild boars. The vast expansion of this Genotype II African swine fever virus (ASFV) across wide-ranging territories and hosts inevitably led to the acquisition of novel mutations. These mutations could be used to track the molecular epidemiology of ASFV, provided that they are unique to strains restricted within a certain area. Whilst whole-genome sequencing remains the gold standard for examining evolutionary changes, sequencing of a single locus with significant variation and resolution power could be used as a rapid and cost-eective alternative to characterize multiple isolates from a single or related outbrea

Genetic characterization of the central variable region in African swine fever virus isolates in the Russian federation from 2013 to 2017

African swine fever virus (ASFV), classified as genotype II, was introduced into Georgia in 2007, and from there, it spread quickly and extensively across the Caucasus to Russia, Europe and Asia. The molecular epidemiology and evolution of these isolates are predominantly investigated by means of phylogenetic analysis based on complete genome sequences. Since this is a costly and timeconsuming endeavor, short genomic regions containing informative polymorphisms are pursued and utilized instead. In this study, sequences of the central variable region (CVR) located within the B602L gene were determined for 55 ASFV isolates submitted from 526 active African swine fever (ASF) outbreaks occurring in 23 different regions across the Russian Federation (RF) between 2013 and 2017. The new sequences were compared to previously published data available from Genbank, representing isolates from Europe and Asia. The sequences clustered into six distinct groups

A guide to molecular characterization of genotype ii African swine fever virus: Essential and alternative genome markers

African swine fever is a contagious viral disease that has been spreading through Europe and Asia since its initial report from Georgia in 2007. Due to the large genome size of the causative agent, the African swine fever virus (ASFV), the molecular epidemiology, and virus evolution are analyzed by employing different markers. Most of these markers originate from single nucleotide polymorphisms or disparities in the copy number of tandem repeat sequences observed during the comparisons of full genome sequences produced from ASFVs isolated during different outbreaks. Therefore, consistent complete genome sequencing and comparative analysis of the sequence data are important to add innovative genomic markers that contribute to the delineation of ASFV phylogeny and molecular epidemiology during active circulation in the field. In this study, the molecular markers currently employed to assess the genotype II ASFVs circulating in Europe and Asia have been outlined

Widespread Reassortment Contributes to Antigenic Shift in Bluetongue Viruses from South Africa

Bluetongue (BT), a viral disease of ruminants, is endemic throughout South Africa, where outbreaks of different serotypes occur. The predominant serotypes can differ annually due to herd immunity provided by annual vaccinations using a live attenuated vaccine (LAV). This has led to both wild-type and vaccine strains co-circulating in the field, potentially leading to novel viral strains due to reassortment and recombination. Little is known about the molecular evolution of the virus in the field in South Africa. The purpose of this study was to investigate the genetic diversity of field strains of BTV in South Africa and to provide an initial assessment of the evolutionary processes shaping BTV genetic diversity in the field. Complete genomes of 35 field viruses belonging to 11 serotypes, collected from different regions of the country between 2011 and 2017, were sequenced. The sequences were phylogenetically analysed in relation to all the BTV sequences available from GenBank, including the LAVs and reference strains, resulting in the analyses and reassortment detection of 305 BTVs. Phylogenomic analysis indicated a geographical selection of the genome segments, irrespective of the serotype. Based on the initial assessment of the current genomic clades that circulate in South Africa, the selection for specific clades is prevalent in directing genome segment reassortment, which seems to exclude the vaccine strains and in multiple cases involves Segment-2 resulting in antigenic shift

Evidence of intragenic recombination in African horse sickness virus

Intragenic recombination has been described in various RNA viruses as a mechanism to increase genetic diversity, resulting in increased virulence, expanded host range, or adaptability to a changing environment. Orbiviruses are no exception to this, with intragenic recombination previously detected in the type species, bluetongue virus (BTV). African horse sickness virus (AHSV) is a double-stranded RNA virus belonging to the Oribivirus genus in the family Reoviridae. Genetic recombination through reassortment has been described inAHSV, but not through homologous intragenic recombination. The influence of the latter on the evolution of AHSV was investigated by analyzing the complete genomes of more than 100 viruses to identify evidence of recombination. Segment-1, segment-6, segment-7, and segment-10 showed evidence of intragenic recombination, yet only one (Segment-10) of these events was manifested in subsequent lineages. The other three hybrid segments were as a result of recombination between field isolates and the vaccine derived live attenuated viruses (ALVs).The Economic Competitive Support Package (ECSP) from National Treasury of the South African Government.http://www.mdpi.com/journal/virusesam2019Veterinary Tropical Disease

Whole-genome sequencing of African swine fever virus from wild boars in the Kaliningrad region reveals unique and distinguishing genomic mutations

IntroductionSince the first report of outbreaks of African swine fever (ASF) in Georgia in 2007, the disease has expanded into Europe, Russia, and Asia, spreading rapidly via contact with infected animals including domestic pigs and wild boars. The vast expansion of this Genotype II African swine fever virus (ASFV) across wide-ranging territories and hosts inevitably led to the acquisition of novel mutations. These mutations could be used to track the molecular epidemiology of ASFV, provided that they are unique to strains restricted within a certain area. Whilst whole-genome sequencing remains the gold standard for examining evolutionary changes, sequencing of a single locus with significant variation and resolution power could be used as a rapid and cost-effective alternative to characterize multiple isolates from a single or related outbreak.Material and methodsASFVs obtained during active ASF outbreaks in the Russian region of Kaliningrad between 2017 and 2019 were examined. Since all of the viruses belonged to Genotype II and no clear differentiation based on central variable region (CVR) sequencing was observed, the whole-genome sequences of nine ASFV isolates from this region were determined. To obtain insights into the molecular evolution of these isolates, their sequences were compared to isolates from Europe, Asia, and Africa.ResultsPhylogenetic analysis based on the whole-genome sequences clustered the new isolates as a sister lineage to isolates from Poland and Germany. This suggests a possible shared origin followed by the addition of novel mutations restricted to isolates from this region. This status as a sister lineage was mirrored when analyzing polymorphisms in MGF-505-5R and MGF-110-7L, whilst a polymorphism unique to sequences from Kaliningrad was identified at locus K145R. This newly identified mutation was able to distinguish the isolates obtained from Kaliningrad with sequences of Genotype II ASFVs available on GenBank.DiscussionThe findings of this study suggest that ASFVs circulating in Kaliningrad have recently obtained this mutation providing an additional marker to the mutations previously described