Search

This study investigates the energy exchanges occurring in the volume and on the surface of water ponds and their influence on the energy consumption of a building. The mathematical model of water ponds is based on coupling the thermal model of the water pond and the airflow model of the surrounding air. It accounts for the heat transfer by radiation, conduction, convection and the latent heat transfer due to water evaporation. The governing equations are numerically solved by a finite difference method for the thermal model and by a finite volume method for the air flow model. The surface temperature and the spatial profiles of temperature and moisture are presented. The effect of the water pond on the cooling energy consumption is discussed. [ABSTRACT FROM AUTHOR]

The green fluorescent protein (GFP) was used as a model protein to study the recombinant protein production by the strain Methylobacterium extorquens ATCC 55366. Scale-up from shake flasks to 20 l fed-batch fermentation was achieved using methanol as a sole carbon and energy source and a completely minimal culture medium. Two different expression vectors were used to express GFP. Clone PCM-GFP containing the vector pCM110 with native promoter of the methanol dehydrogenase PmxaF produced approximately 100-fold more GFP than the clone PRK-GFP containing the vector pRK310 with the heterogeneous promoter Plac. Several fed-batch fermentations with and without selective pressure (tetracycline) were run in a 20 l stirred tank fermenter using the two different clones of M. extorquens. The methanol concentration was monitored with an on-line semiconductor gas sensor in the culture broth. It was maintained at a non-toxic level of 1.4 g l−1 with an adaptative control which regulates the methanol feed rate. The same growth profile was achieved in all fermentations. The maximum growth rate (μmax) was 0.18 h−1 with an overall yield (YX/S) of 0.3 g g−1 methanol. With this high cell density fermentation process, we obtained high levels (up to 4 g l−1) of GFP with the clone PCM-GFP. The maximum specific GFP production (YGFP/X) with this clone was 80 mg g−1 representing approximately 16% of the total cell protein. Additional feeding of pure oxygen to the fermenter permitted a longer phase of exponential growth but had no effect on the total yields of biomass and GFP. The specific GFP production of clone PCM-GFP remained unaffected in the presence or absence of selective pressure (tetracycline), within the initial 50 h of the fermentation culture. These results suggest that M. extorquens ATCC 55366 could be an interesting candidate for overexpression of recombinant proteins. [Copyright &y& Elsevier]

Copyright of World Journal of Microbiology & Biotechnology is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Lectins were used to characterize glycoconjugates on the cell surface of Treponema denticola, a suspected periodontopathogen. Bacteria were first screened by light microscopy using fluorescein isothiocyanate-coupled lectins. Wheat germ agglutinin (WGA) showed a high reactivity to T. denticola. While the WGA-binding activity was accentuated following heating or detergent treatments of bacterial cells, the reaction was inhibited by incorporation of competing carbohydrates. Scanning and transmission electron microscope studies were conducted in order to characterize the distribution of the WGA-binding sites on the cell surface of T. denticola. Data from these studies confirmed that heat treatment increases the percentage of labeled profiles and suggest that the WGA-binding sites are concentrated on specific regions on the spirochete surface. Initial biochemical analysis indicated that the high reactivity to WGA resides in a peptidoglycan fraction. [ABSTRACT FROM AUTHOR]