Papers by Oswald Gekko Kierkegaard
Microalgae have been studied as natural resources for a number of applications, most particularly... more Microalgae have been studied as natural resources for a number of applications, most particularly food, animal feed, biofuels, pharmaceuticals, and nutraceuticals. In addition to the intracellular compounds of interest, microalgae can also excrete various extracellular polymeric substances (EPS) into their immediate living environment during their life cycle to form a hydrated biofilm matrix. These microalgal EPS mainly consist of polysaccharides, proteins, nucleic acids and lipids. Most notably, EPS retain their stable matrix structure and form a 3-D polymer network for cells to interact with each other, and mediate their adhesion to surfaces. EPS also play a role as extracellular energy and carbon sinks. They are also abundant source of structurally and compositionally diverse biopolymers which possess unique bioactivities for special high-value applications, specifically as antivirals, antitumor agents, antioxidants, anticoagulants and antiinflammatories. Their superior rheological properties also make microalgal EPS particularly useful in mechanical engineering (e.g., biolubricants and drag reducers) and food science/engineering (e.g., thickener and preservatives) applications. The chemical composition and structure of EPS appear to correlate with their applications, but the fundamentals of such relationship are not well understood. This article summarizes previous research on microalgal EPS derived from green algae, diatoms and red algae, including compositions/functions/structure, production, and potential applications. The importance of exopolysaccharides and EPS proteins, with their particular metabolic characteristics, are also described because of their potential highvalue applications. This review concludes with potential future research areas of microalgal EPS.
Extracellular polymeric substances comprised of average molecule size 1264.354 m, exhibited chara... more Extracellular polymeric substances comprised of average molecule size 1264.354 m, exhibited characteristic diffraction peaks at 6.025 • , 9.675 • , 22.775 • and 28.475 • with d-spacing 14.74755, 9.36297, 3.88747 and 3.11512Å, respectively. EDX confirms the presence of sulphate (2.7%) and 1 H NMR reveals uronic acid, primary amine, aromatic-compounds, halides, aliphatic alkyl and sulfides. EPSs were thermostable upto 270 • C with CI xrd 0.12 and CI DSC 0.18. The dynamic viscosity is significantly high at pH 3.0 and decreases concomitantly with shear rate, confirming pseudoplastic rheological property. MALDI TOF-TOF represents a series of masses in linear mode corresponding to mass of pentose and hexose with ions. The positive ion reflector mode exhibited low mass peaks (m/z) corresponding to oligosaccharide and higher peaks for polysaccharide consist of different ratio of pentose and hexose associated with ions. EPSs allow further exploration of D. salina as potential EPSs producer and make it a promising candidate for biotechnological and industrial exploitation.
Algae biomass-fed wastewaters are a promising source of lipid and bioenergy manufacture, revealin... more Algae biomass-fed wastewaters are a promising source of lipid and bioenergy manufacture, revealing substantial end-product investment returns. However, wastewaters would contain lytic pathogens carrying drug resistance detrimental to algae yield and environmental safety. This study was conducted to simultaneously decipher through highthroughput advanced Illumina 16S ribosomal RNA (rRNA) gene sequencing, the cultivable and uncultivable bacterial community profile found in a single sample that was directly recovered from the local wastewater systems. Samples were collected from two previously documented sources including anaerobically digested (AD) municipal wastewater and swine wastewater with algae namely Chlorella spp. in addition to control samples, swine wastewater, and municipal wastewater without algae. Results indicated the presence of a significant level of Bacteria in all samples with an average of approximately 95.49% followed by Archaea 2.34%, in local wastewaters designed for algae cultivation. Taxonomic genus identification indicated the presence of Calothrix, Pseudomonas, and Clostridium as the most prevalent strains in both local municipal and swine wastewater samples containing algae with an average of 17.37, 12.19, and 7.84%, respectively. Interestingly, swine wastewater without algae displayed the lowest level of Pseudomonas strains < 0.1%. The abundance of some Pseudomonas species in wastewaters containing algae indicates potential coexistence between these strains and algae microenvironment, suggesting further investigations. This finding was particularly relevant for the earlier documented adverse effects of some nosocomial Pseudomonas strains on algae growth and their multidrug resistance potential, requiring the development of targeted bioremediation with regard to the beneficial flora.
Ecology 92, 218 (2011). Acknowledgments: I thank J. Hoogland for encouraging me to reexamine my i... more Ecology 92, 218 (2011). Acknowledgments: I thank J. Hoogland for encouraging me to reexamine my information on dispersal; my 150+ research assistants over the 31 years of research (especially my four offspring);
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Papers by Oswald Gekko Kierkegaard