1,720,961 research outputs found
Evaluation of chitosan–coated magnetic nanoparticle-immobilized thermostable hemicellulases for enhanced saccharification and production of bioethanol
No full textSubmitted in complete fulfillment for the Degree of Master of Applied Sciences in Biotechnology, Durban University of Technology, Durban, South Africa, 2022.Enhancing the efficiency of saccharification of pentose and hexose sugars present in
lignocellulosic biomass is a major bottleneck for industrial bioethanol production. This problem
can be addressed by a concerted effort combining nanotechnology, enzymology and fermentation
technology. Functionalized chitosan-coated magnetic nanoparticles (CCMNPs) were prepared and
used for co-immobilization of purified xylan hydrolysing xylanase and xylosidase from the
thermophilic fungus Thermomyces lanuginosus SSBP for the release of xylose. Stability studies
revealed that immobilized enzymes were more stable than free enzymes over a wide range of pH
(4.0 – 7.0) and temperature (40 – 90 °C) for xylanase and 30 – 80 °C for xylosidase. The optimum
activity of the co-immobilized enzymes shifted slightly as compared to the free enzymes, with coimmobilized xylanase and xylosidase showing optimum activity at pH 6.5 and 6.0, respectively.
The study showed sustained production of xylose as the major fermentable sugar under repeated
batch and fed-batch saccharification of lignocellulosic biomass. Statistical optimization of
saccharification of 1% xylan using response surface methodology indicated the enhanced release
of xylose at 50 °C, pH 7.0 and enzyme dose of 60 U/mL xylanase and 30 U/mL xylosidase. Finally,
liberated xylose was fermented with Scheffersomyces stipitis to yield bioethanol.
Formulation and in vitro analysis of essential oil blended (Cymbopogon citratus, Syzgium aromaticum and Melaleuca alternifolia) biocompatible hand sanitizer against common bacterial pathogens
No full textSubmitted in fulfillment of the requirements of the degree of Master of Somatology, Durban University of Technology, Durban, South Africa, 2024.ABSTRACT Essential oils (EOs) are predominantly known for their use in aromatherapy, cosmetic, food and pharmaceutical industries. Combination of EOs may result in holistic synergistic effects due to a blended biocompatible mixture. In this study, three EOs were selected out of the seven EOs tested for their efficacy against Gram-positive and Gram-negative bacteria based on the results of disc diffusion. The Minimum Bactericidal Concentration (MBC) of EOs from Cymbopogon citratus (lemongrass), Melaleuca alternifolia (tea tree) and Syzgium aromaticum (clove) were determined against Micrococcus luteus, Bacillus subtilis, Bacillus cereus, Klebsiella pneumoniae and Escherichia coli ATCC 11775. The EOs were analysed using gas chromatography mass spectrometry (GC-MS) to identify the volatile organic compounds. Geranial, neral, neryl acetate and β-caryophyllene were present in highest concentrations among 48 chemicals identified in lemon grass essential oil (LGEO). GC-MS identified 17 chemical compounds in clove EO (CEO) with eugenol, eugenol acetate and β-caryophyllene present in highest concentrations. A total of 52 compounds were identified with terpineol-4, γ-terpinene, α-terpipene and 1,8-cineole (eucalyptol) being the most prevalent compounds in tea tree EO (TTEO). Response surface methodology (RSM) using central composite design (CCD) was used to develop a mathematical model that determined the optimal concentrations of LGEO, TTEO and CEO as 0.10%, 0.11% and 0.10%, respectively. This investigation highlighted the importance of microbiological techniques and statistical optimization tools to study the synergistic effect of selected EOs towards developing a combined EO - based antibacterial treatment technology. Overall, this study showed the potential of developing a biocompatible hand sanitizer which resulted in marked log reduction of bacteria. Further study on the efficacy of the developed EO-mixture against viruses, fungi and nematodes will provide useful scientific knowledge.
Production, characterisation and applications of a thermo-acid-stable phytase from Enterobacter sp. ACSS
No full textSubmitted in complete fulfillment for the Degree of Master of Applied Sciences in Biotechnology, Durban University of Technology, Durban, South Africa, 2016.A bacterial strain producing an extracellular phytase was identified as Enterobacter sp. ACSS. Optimization of process parameters using statistical methods such as Plackett-Burman design (PBD), the steepest ascent method, and response surface methodology (RSM) significantly improved phytase production by 4.6–fold in shake-flasks. In addition, an overall 1.9-fold increase in phytase production was attained in fed-batch fermentations in a 5 l laboratory fermenter, respectively. The purified 62 kDa phytase from Enterobacter sp. ACSS was active between 40 to 80°C and an acidic pH range of 2.0 to 6.0 with half-life of 693 and 577.5 min at 60°C and pH 2.0, respectively. Additionally, the enzyme is fairly stable with proteolytic enzymes under physiological conditions. It was activated by Ca+2, Mg+2 and Mn+2 while inhibition was caused by Zn+2, Cu+2, Fe+2, Pb+2, Co+2, Ba+2 and surfactants. The Km, Vmax and Kcat observed were 0.21 mM, 131.58 nmol mg-1s-1 and 1.64 × 103 s-1, respectively. The enzyme released inorganic phosphate from animal feed (4.0-6.62 mg/g of diet) and insoluble metal-phytates (45-219 µg/ml) and was effective in improving the characteristics of brown bread. Overall, this study shows that Enterobacter sp. ACSS has the potential to produce significant titres of a thermo- and acid-stable phytase and can be applied in dephytinizing animal feeds, and the baking industry.
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
Development of chitosan biopolymer films by fungal fermentation of waste substrates
No full textSubmitted in fulfillment for the Degree of Master of Applied Science in Biotechnology, Durban University of Technology, Durban, South Africa, 2024.Zygomycetes are known for their relatively high chitosan content (approximately 10% m/m) in comparison with other fungal genera. In this study, Mucor circinelloides was grown on the following industrial waste substrates: corn steep liquor (CSL); soft drink overflow spillage waste (DBW); and sugarcane molasses (MOL). Biomass production on waste substrates was statistically optimized by Plackett-Burman design in conjunction with Response Surface Methodology, followed by validation of the model. DBW hindered fungal biomass growth and was found to be a statistically insignificant variable and therefore omitted from further optimizations. The validated model produced a biomass of 77.87 g/L, a 2.65-fold increase over the highest-yielding unoptimized medium. Fungal biomass obtained after batch fermentation was subjected to acid-alkaline treatment for chitin extraction from the cell wall and deacetylation of the chitin to chitosan. A yield of 8-9% chitosan was obtained from the fungal biomass. FTIR spectroscopic analysis was conducted on the extracted fungal chitosan to compare extracted chitosan against commercial chitosan and chitosan monomer. The waste-grown, fungal-derived chitosan profiles were similar to those of commercial crustacean chitosan. The extracted chitosan was used in conjunction with additives and solvent systems to create biopolymer variants with differing properties. A library of data from the chitosan biopolymer variants was generated with considerable differences in characteristics based on their composition. Improvements in sample #11 (the most modified formulation) in contrast to the most common chitosan biopolymer film composition used in literature (sample #9), included a 3.37-fold improvement in the static force required to break the film. There was a 3.39-fold increase in tensile strength and an 11-fold reduction in elongation (%) and elongation rates. The creation of these variants will allow the use of these chitosan biopolymers for specific industrial applications.
Production, characterization and applications of two distinct phytases from Thermomyces lanuginosus SSBP
No full textSubmitted in fulfillment for the Degree of Master of Applied Sciences in Biotechnology, Durban University of Technology, Durban, South Africa, 2018.Phosphorous (P) is an essential element which is primarily stored as phytic acid in plants and exits as dominating form of organic P in soil. The phytate anion has strong chelation properties and can bind with essential metal ions, proteins, starch and several biomolecules under physiological conditions, and accumulates in soil due to strong binding with soil solid phase. Phytases are enzymes that hydrolyse phytate in stepwise manner to release inositol phosphates and orthophosphate, thereby releasing the chelated molecule.
In this study, we report two phytases (Tlphy1 and Tlphy2) from a thermophilic compost-dwelling filamentous fungus, Thermomyces lanuginosus SSBP. The total phytase production was enhanced by 8.56-fold in submerged fermentation after statistical optimization, which was further improved in fed-batch cultivations. Tlphy1 and Tlphy2 were purified to homogeneity with an overall purification of 24.7- and 18.7-fold with 5.16% and 6.4% yield, respectively. Tlphy1 was estimated to be 49 kDa and was optimally active at 55°C and pH 5.0, while Tlphy2 was purified as a 60 kDa protein showing optimal activity at 50°C and pH 2.5. Tlphy1 and Tlphy2 were stable over wide ranges of pH and temperature with a half-life of 138.6 and 58.72 min, respectively at 70°C. The applicability of these phytases was investigated for the improvement of bioethanol production using Colocasia esculenta, dephytinisation of a local non-alcoholic beverage, mageu and in improving growth promotion of common bean plants. Tlphy1 reduced phytate content in Colocasia esculenta starch from 1.43 mg/g to 0.05 mg/g that resulted in an improvement in the availability of fermentable sugars with a concomitant reduction in viscosity and 1.59-fold improvement in ethanol production. Supplementation of 50 U Tlphy2 in 100 g ical industries.of mageu efficiently reduced the total fermentation time from 24 h to 16 h with significant dephytinisation and marked enhancement of essential metal ions. Additionally, Tlphy2 also promoted germination of bean seeds, while an enzyme dose of 25 U markedly improved root and shoot length of bean plants. Overall, the two distinct phytases from T. lanuginosus SSBP have multifarious applicability, and therefore can be of major interest to several biotechnology.
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
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