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    ABSTRACT: Control of dental plaque-related diseases has traditionally relied on non-specific removal of plaque by mechanical means. As our knowledge of oral disease mechanisms increases, future treatment is likely to be more targeted, for example at small groups of organisms, single species or at key virulence factors they produce. The aim of this review is to consider the current status as regards novel treatment approaches. Maintenance of oral hygiene often includes use of chemical agents; however, increasing problems of resistance to synthetic antimicrobials have encouraged the search for alternative natural products. Plants are the source of more than 25% of prescription and over-the-counter preparations, and the potential of natural agents for oral prophylaxis will therefore be considered. Targeted approaches may be directed at the black-pigmented anaerobes associated with periodontitis. Such pigments provide an opportunity for targeted phototherapy with high-intensity monochromatic light. Studies to date have demonstrated selective killing of Porphyromonas gingivalis and Prevotella intermedia in biofilms. Functional inhibition approaches, including the use of protease inhibitors, are also being explored to control periodontitis. Replacement therapy by which a resident pathogen is replaced with a non-pathogenic bacteriocin-producing variant is currently under development with respect to Streptococcus mutans and dental caries.
    International Journal of Antimicrobial Agents 10/2008; 33(1):8-13.
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    ABSTRACT: In a CO2-limited algal culture, grown in a tubular loop photobioreactor, the maximum rate of CO2 absorption increased about 1.5-fold when the culture pH value was increased from 6.5 to 7.5 with a fixed initial PCO2. The mean volumetric CO2 transfer coefficient (KLa) increased about 1.8-fold. The bicarbonate ion concentration would be increased 10-fold by the pH increase. The effect of pH on the absorption rate is attributed to changes in either the CO2 diffusivity, the gas bubble size, or the CO2 reaction kinetics at the gas/liquid boundary.
    Journal of Chemical Technology and Biotechnology. Biotechnology. 04/2008; 34(1):28 - 32.
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    ABSTRACT: The photosynthetic efficiency (PE) of a growing algal culture was determined from the growth yield (Y), that is, biomass produced/light absorbed and the calorific value of the biomass (k); PE = kY. To obtain the maximum photosynthetic efficiency the algae were grown in light-limited chemostat cultures in urea-mineral salts media plus CO2 and steady-states were obtained at different specific growth rates. With a given light input the biomass output rate was independent of the specific growth rate up to at least 70% of the maximum specific growth rate. The photosynthetic efficiency was independent of the incident light intensity over the range studied, 5.3–21.3 W m−2. The light source had a spectral range of 400–700 nm and its mean wavelength was assumed to be 575 nm. The values of the maximum growth yields (YG, g dry weight kJ−1) were 0.0153 for the Sorokin Chlorella strain 211/8k and 0.0206 for a newly selected mixed culture MA003 which consisted of an alga and three species of heterotrophic bacteria. The maintenance energy (m) of the mixed culture MA003 was in the range 0–0.32 kJ g−1 dry weight h−1 and the specific maintenance rate (mYG) was in the range 0–0.0066 h−1. In Chlorella strain 211/8k the maximum PE was 34.7% which corresponds to a quantum demand (n) of 6.6 per O2 molecule evolved. In the mixed culture MA003 the maximum PE was 46.8% with 95% confidence limits, 42.7–51.5. This PE value corresponds to a quantum demand (n) of 4.8 per O2 molecule evolved. These results call in question the current model of photosynthesis which predicts that the maximum PE with absorbed light of mean wavelength 575 nm should not exceed 29% and the minimum quantum demand, n = 8. From our results with culture MA003 it is deduced that the maximum practicable storage of total solar energy by algal biomass growth in vitro is 18%.
    Journal of Chemical Technology and Biotechnology. 05/2007; 30(1):25 - 34.
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    ABSTRACT: By means of chemostat culture and automatic control of pH and dissolved oxygen tension the penicillin fermentation was controlled so that the partial pressure of carbon dioxide (Pco2) in the gas phase was the only variable. This reveals that under the conditions used carbon dioxide strongly inhibits penicillin production. The synthesis rate (units/mg dry mycelium x h) was decreased about 50% by a Pco2 of 0.08 atm.
    Journal of Applied Chemistry and Biotechnology 04/2007; 25(10):781 - 783.
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    ABSTRACT: Starch and amylose utilisation by K. aerogenes under chemostat conditions were studied as models of polymer degradation in the chemostat. The effects of growth rate on the process and upon cellular concentrations of α-amylase and pullulanase were determined. The debranching enzyme (pullulanase) activity was greatest when the highly branched polymer (starch) limited growth. The pullulanase activity varied inversely with the dilution rate when starch limited growth but increased with dilution rate when nitrogen limited growth. Pullulanase seems to be the enzyme controlling growth rate. The polymer substrate affinities (Ks values) expressed on a molar basis were about the same as the values observed for monomers.
    Journal of Applied Chemistry and Biotechnology 04/2007; 25(4):297 - 304.
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    ABSTRACT: Satisfactory growth of Bacillus macerans and high activities of cyclodextrin glycosyltransferase (CGT) were obtained in media containing potato extract. The appearance of CGT in culture supernatant fluids during the stationary phase of growth was not due to autolysis, since intracellular levels of the enzyme were very low throughout the cultivation. When cell growth was limited by the starch concentration in the medium, CGT activity remained low during the logarithmic phase of growth but high activities appeared suddenly in the supernatant fluid when growth ceased. Negligible activities were produced by cultures growing in a nitrogen-deficient medium in which starch was present in excess. CGT therefore appears to be a true extracellular enzyme, produced in response to exhaustion of the starch from the medium. A simple fractionaltion procedure was developed for concentrating the CGT from culture supernatant fluids. This enzyme preparation was used to convert 20% (w/v) starch solutions to cyclodextrins in 24 h and the cyclodextrins recovered were equivalent to 55% of the original starch.
    Journal of Applied Chemistry and Biotechnology 04/2007; 21(11):330 - 334.
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    ABSTRACT: The shortage of fossil fuels restricts the world supply of reduced carbon compounds and energy sources. Biotechnology offers the most feasible route to renewing the supplies of reduced carbon compounds. This involves recycling of CO2 through photosynthesis. Conventional agriculture has little or no potential for supplying biomass and its derivatives on sufficient scale to offer an alternative to the fossil fuels. The agricultural wastes, on the whole, are intractable to conversion into useful carbon and energy sources and in any case are not available in amounts to provide a significant alternative to the fossil fuels. In contrast, microbial photosynthesis, optimised in photobioreactors, has vast potential to provide organic matter on a scale to match the consumption of fossil fuels. The quantitative study of microbial photosynthesis as a biotechnological route to biomass has been neglected. As a result there is a chaos of conflicting data on fundamental parameters, for example, the photosynthetic efficiency of biomass production. New photosynthetic biotechnology with fully controlled continuous-culture systems is providing unequivocal values for the parameters. For the scale-up of microbial photosynthesis a tubular-loop reactor is proposed.
    Journal of Chemical Technology and Biotechnology. 04/2007; 32(1):198 - 202.
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    ABSTRACT: Our understanding of the relationship between microbes and their animal hosts have changed dramatically in the last decade. The development of powerful new molecular methods as well as different animal models, particularly germ free rodents, has enabled precise characterisation of the ways in which commensal bacteria in the gastrointestinal tract and other areas interact with their hosts. It is now clear that animal development, far from being genetically determined is intimately bound up with the microbial flora of that particular animal. In germ free mice, the addition of Bacteroides thetaiotaomicron mediates the maturation and function of the gastrointestinal tract in several different ways. Similarly Bacteroides fragilis directs the development of the immune system both in and outside the gastrointestinal tract. The relevance of these findings and others to our understanding of human development and disease is discussed.
    Early Human Development 04/2007; 83(3):165-70.
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    ABSTRACT: The nature of the interaction between Porphyromonas gingivalis and the multifunctional peptides adrenomedullin and calcitonin gene-related peptide (CGRP) was investigated. Growth of P. gingivalis was not inhibited in the presence of either of these peptides [minimal inhibitory concentration (MIC)>250 microg mL(-1)]. The ability of the arginine- and lysine-specific proteases from P. gingivalis to breakdown these peptides was investigated. Adrenomedullin and CGRP were incubated with culture supernatants from wild-type and protease gene knockout strains. No significant effect on antimicrobial activity against the indicator organism Escherichia coli BUE55 was found (MIC=6.25 microg mL(-1) in all cases). The role of anionic components on the surface of P. gingivalis, which may alter binding of these cationic peptides, was also investigated in relation to adrenomedullin. Growth of gene knockout strains lacking surface polysaccharide and capsule components was not inhibited (MIC>250 microg mL(-1)). It is suggested that a lack of sensitivity to adrenomedullin and CGRP may enable P. gingivalis to persist in the oral cavity and cause disease.
    FEMS Immunology & Medical Microbiology 02/2007; 49(1):91-7.
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    ABSTRACT: The radioactive melanin used in this study was extracted from the cell walls of the fungus Aspergillus nidulans after growth in the presence of 14C-labelled precursors. The counting systems investigated comprised solid samples suspended in a liquid scintillator with or without silica gel, solubilized samples blended in a liquid scintillator and solubilized samples adsorbed on to glass-fibre discs wich were suspended in a liquid scintillator. Results obtained by counting solid samples with an end window detector are compared with the liquid scintillation data. High counting efficiencies were realized with the glass-fibre disc method which is recommended for the assay of soluble samples. Liquid scintillation counting of silica gel suspensions was vastly superior to end window counting for the assay of solid samples. The data suggest that 14C-labelled materials of a particulate or highly pigmented nature can be counted with high efficiency in a liquid scintillation system.
    Journal of Labelled Compounds 07/2006; 4(2):181 - 191.
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