On-line coupling of a miniaturized bioreactor with capillary electrophoresis, via a membrane interface, for monitoring the production of organic acids by microorganisms

Capillary electrophoresis (CE) can be a valuable tool for on-line monitoring of bioprocesses. Production of organic acids by phosphorus-solubilizing bacteria and fermentation of UHT milk were monitored and controlled by use of a membrane-interfaced dialysis device and a home-made microsampler for a capillary electrophoresis unit. Use of this specially designed sampling device enabled rapid consecutive injections without interruption of the high voltage. No additional sample preparation was required. The time resolution of monitoring in this particular work was approximately 2 h, but could be reduced to 2 min. Analytes were detected at low microg mL(-1) levels with a reproducibility of approximately 10%. To demonstrate the potential of CE in processes of biotechnological interest, results from monitoring phosphate solubilization by bacteria were submitted to qualitative and quantitative analysis. Fermentation experiments on UHT milk showed that monitoring of the processes by CE can provide good resolution of complex mixtures, although for more specific, detailed characterization the identification of individual substances is needed.     

Synthesis and gas-sensing properties of phenylhydrazine-functionalized single wall carbon nanotubes in polymer matrix

Gas sensor material was prepared by encapsulation of functionalized single-walled carbon nanotubes (SWCNT) into a gas-permeable polymer poly(1-trimethylsilyl-1-propyne) (PTMSP). A phenylhydrazino group was used for the functionalization of SWCNTs to improve their solubility and compatibility with polymers. Syntheses were carried out in aqueous surfactant solutions and in pure phenylhydrazine without surfactant. Two different temperatures (24 and 50°C) and two surfactants (sodium dodecyl sulfate and tricaprylmethylammonium chloride — Aliquat®336) were compared. Functionalized SWCNTs were characterized by X-ray photoelectron (XPS), Raman and Fourier transform infrared (FTIR) spectroscopy. Analyses showed that the synthesis at higher temperature in pure phenylhydrazine resulted in the highest functionalization yield. Phenylhydrazine itself proved to be a good solvent for SWCNTs. The functionalized nanotubes were soluble in organic solvents that under the same conditions were appropriate solvents for polymers. The sensitivity of functionalized SWCNT-PTMSP thin film composite to NO₂ gas at room temperature was significantly higher than that of the similar sensor material containing the pristine SWCNTs.