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[en] Accumulation of succinate as a fermentation product of Fusobacterium varium was enhanced when the anaerobic bacterium was grown on complex peptone medium supplemented with fumarate. Residual substrates and fermentation products were determined by proton NMR spectroscopy. Cells collected from the fumarate-supplemented medium (8–10 h after inoculation) supported the conversion of fumarate to succinate when suspended with fumarate and a co-substrate (glucose, sorbitol, or glycerol). Succinate production was limited by the availability of fumarate or reducing equivalents supplied by catabolism of a co-substrate via the Embden-Meyerhof-Parnas (EMP) pathway. The choice of reducing co-substrate influenced the yield of acetate and lactate as side products. High conversions of fumarate to succinate were achieved over pH 6.6–8.2 and initial fumarate concentrations up to 300 mM. However, at high substrate concentrations, intracellular retention of succinate reduced extracellular yields. Overall, the efficient utilization of fumarate (≤ 400 mM) combined with the significant extracellular accumulation of succinate (corresponding to ≥ 70% conversion) indicated the effective utilization of fumarate as a terminal electron acceptor by F. varium and the potential of the methodology for the bioproduction of succinate.
[en] A microfabricated magnetic sifter has been designed and fabricated for applications in biological sample preparation. The device enables high-throughput, high-gradient magnetic separation of magnetic nanoparticles by utilizing columnar fluid flow through a dense array (∼5000/mm2) of micropatterned slots in a magnetically soft membrane. The potential of the sifter for separation of magnetic nanoparticles conjugated with capture antibodies is demonstrated through quantitative separation experiments with CD138-labeled MACS nanoparticles. Capture efficiencies ranging from 28% to 37% and elution efficiencies greater than 73% were measured for a single pass through the sifter.
[en] We present proof-of-concept experiments and modeling towards a high-sensitivity magnetic microarray which 'tags' a DNA fragment (or other biological samples) with a high-moment magnetic nanoparticle (NanoTag), which is in turn detected by a high-sensitivity spin valve (SV) or magnetic tunnel junction (MTJ) detector array. The detector can count the number of magnetic tags with a resolution of 1-20 magnetic NanoTags, potentially counting individual biomolecules