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Cells L (cell + l)
Selected AbstractsOptimization of Cyclodextrin Glycosyltransferase Production from KlebsiellapneumoniaeAS-22 in Batch, Fed-Batch, and Continuous CulturesBIOTECHNOLOGY PROGRESS, Issue 6 2003Bharat N. Gawande Production of a novel cyclodextrin glycosyltransferase (CGTase) from Klebsiella pneumoniaeAS-22 strain, which converts starch predominantly to ,-CD at high conversion yields, in batch, fed-batch, and continuous cultures, is presented. In batch fermentations, optimization of different operating parameters such as temperature, pH, agitation speed, and carbon-source concentration resulted in more than 6-fold increase in CGTase activity. The enzyme production was further improved by two fed-batch approaches. First, using glucose-based feed to increase cell density, followed by starch-based feed to induce enzyme production, resulted in high cell density of 76 g dry cell weight/L, although the CGTase production was low. Using the second approach of a single dextrin-based feed, 20-fold higher CGTase was produced compared to that in batch fermentations with media containing tapioca starch. In continuous operation, more than 8-fold increase in volumetric CGTase productivity was obtained using dextrin-based media compared to that in batch culture using starch-based media. [source] Periphyton as alternative food source for the filter-feeding cladoceran Daphnia magnaFRESHWATER BIOLOGY, Issue 1 2009SILVANA SIEHOFF Summary 1., Daphnia magna, a well-studied primary consumer, is mainly known as a filter feeder. In this study, we investigated the ability of D. magna to use periphyton as an alternative food source to phytoplankton. We examined the development of laboratory populations fed with different food sources (Desmodesmus subspicatus and/or periphyton or neither) over a period of 42 days, and observed the behaviour of the daphnids. 2.,The addition of periphyton to phytoplankton food led to an increase of daphnid population biomass. When fed with periphyton as the only food source, a small but stable D. magna population developed. 3.,The behaviour of daphnids fed with both food sources revealed a preference for feeding on D. subspicatus. Only below a concentration of D. subspicatus of approximately 0.05 mg C L,1 (0.4 × 107 cells L,1) did D. magna use periphyton as an alternative food source. 4.,Periphyton showed distinct reactions to grazing by D. magna. The thickness of the periphyton layer was reduced from about 4 to 1 mm and we observed a change in species composition due to grazing. 5.,The ability of D. magna to graze on periphyton could serve to stabilize its population density and reinforce its competitive advantage over other cladocerans. By switching between food sources, D. magna can act as a coupler between pelagic and benthic habitats and food webs. [source] Post-Impoundment Biomass and Composition of Phytoplankton in the Yangtze RiverINTERNATIONAL REVIEW OF HYDROBIOLOGY, Issue 3 2007Hui Zeng Abstract Damming, and thus alteration of stream flow, promotes higher phytoplankton populations and encourages algal blooms (density >106 cells L,1) in the Three Gorges Reservoir (TGR). Phytoplankton composition and biomass were studied in the Yangtze River from March 2004 to May 2005. 107 taxa were identified. Diatoms were the dominant group, followed by Chlorophyta and Cyanobacteria. In the Yangtze River, algal abundance varied from 3.13 × 103 to 3.83 × 106 cells L,1, and algal biomass was in the range of 0.06 to 659 mg C m,3. Levels of nitrogen, phosphorus and silica did not show consistent longitudinal changes along the river and were not correlated with phytoplankton parameters. Phytoplankton abundance was negatively correlated with main channel discharge (Spearman r = ,1.000, P < 0.01). Phytoplankton abundance and biomass in the Yangtze River are mainly determined by the hydrological conditions rather than by nutrient concentrations. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Metabolic fate of l -lactaldehyde derived from an alternative l -rhamnose pathwayFEBS JOURNAL, Issue 20 2008Seiya Watanabe Fungal Pichia stipitis and bacterial Azotobacter vinelandii possess an alternative pathway of l -rhamnose metabolism, which is different from the known bacterial pathway. In a previous study (Watanabe S, Saimura M & Makino K (2008) Eukaryotic and bacterial gene clusters related to an alternative pathway of non-phosphorylated l -rhamnose metabolism. J Biol Chem283, 20372,20382), we identified and characterized the gene clusters encoding the four metabolic enzymes [l -rhamnose 1-dehydrogenase (LRA1), l -rhamnono-,-lactonase (LRA2), l -rhamnonate dehydratase (LRA3) and l -2-keto-3-deoxyrhamnonate aldolase (LRA4)]. In the known and alternative l -rhamnose pathways, l -lactaldehyde is commonly produced from l -2-keto-3-deoxyrhamnonate and l -rhamnulose 1-phosphate by each specific aldolase, respectively. To estimate the metabolic fate of l -lactaldehyde in fungi, we purified l -lactaldehyde dehydrogenase (LADH) from P. stipitis cells l -rhamnose-grown to homogeneity, and identified the gene encoding this enzyme (PsLADH) by matrix-assisted laser desorption ionization-quadruple ion trap-time of flight mass spectrometry. In contrast, LADH of A. vinelandii (AvLADH) was clustered with the LRA1,4 gene on the genome. Physiological characterization using recombinant enzymes revealed that, of the tested aldehyde substrates, l -lactaldehyde is the best substrate for both PsLADH and AvLADH, and that PsLADH shows broad substrate specificity and relaxed coenzyme specificity compared with AvLADH. In the phylogenetic tree of the aldehyde dehydrogenase superfamily, PsLADH is poorly related to the known bacterial LADHs, including that of Escherichia coli (EcLADH). However, despite its involvement in different l -rhamnose metabolism, AvLADH belongs to the same subfamily as EcLADH. This suggests that the substrate specificities for l -lactaldehyde between fungal and bacterial LADHs have been acquired independently. [source] | ||||||||||