Biomedical subjects

Fukiko Kubota

Publications and source records attributed to Fukiko Kubota.

4 recordsLinked to original sources

PubMed2005

Optical resolution of various amino acids using a supported liquid membrane encapsulating a surfactant-protease complex.

We have encapsulated a surfactant-protease complex (the main protease used being alpha-chymotrypsin) in an organic phase of a supported liquid membrane (SLM) for the optical resolution of various amino acids. L-Isomers of amino acids were enantioselectively permeated through the SLM. The mechanism of the amino acid permeation through the SLM was considered to be as follows; an L-amino acid was enantioselectively esterified with ethanol by a surfactant-protease complex encapsulated in the SLM, and the resulting L-amino acid ethyl ester dissolved into the organic phase of the SLM and diffused across the SLM. Another surfactant-alpha-chymotrypsin complex in the receiving phase catalyzed ester hydrolysis to produce the initial L-amino acid and ethanol, which are water-soluble. Thus, the L-amino acid was selectively transported to the receiving phase through the SLM on the basis of the molecular recognition of the surfactant-protease complex in the SLM. It was found that the catalytic activity and enantioselectivity of the surfactant-protease complex governed the permeate flux of amino acids and the enantiomeric excess in the membrane separation.

Amino Acids↗

PubMed2004

Liquid membrane operations in a microfluidic device for selective separation of metal ions.

A three-phase flow, water/n-heptane/water, was constructed in a microchannel (100-microm width, 25-microm depth) on a glass microchip (3 cm x 7 cm) and was used as a liquid membrane for separation of metal ions. Surface modification of the microchannel by octadecylsilane groups induced spontaneous phase separation of the three-phase flow in the microfluidic device, which allows control of interfacial contact time and off-chip analysis using conventional analytical apparatus. Prior to the selective transport of a metal ion through the liquid membrane in the microchannel, the forward and backward extraction of yttrium and zinc ions was investigated in a two-phase flow on a microfluidic device using 2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester (commercial name, PC-88A) as an extractant. The extraction conditions (contact time of the two phases, pH, extractant concentration) in the microfluidic device were examined. These investigations demonstrated that the conventional methodology for solvent extraction of metal ions is applicable to solvent extraction in a microchannel. Finally, we employed the three-phase flow in the microchannel as a liquid membrane and observed the selective transport of Y ion through the liquid membrane. In the present study, we succeeded, for the first time, in the selective separation of a targeted metal ion from an aqueous feed solution to a receiving phase within a few seconds by employing a liquid membrane formed in a microfluidic device.

Cations↗

PubMed2003

Enzymatic degradation of p-chlorophenol in a two-phase flow microchannel system.

Enzymatic degradation of p-chlorophenol was carried out in a two-phase flow in a microchannel (100 microm width, 25 microm depth) fabricated on a glass plate (70 mm x 38 mm). This is the first report on the enzymatic reaction in a two-phase flow on a microfluidic device. The surface of the microchannel was partially modified with octadecylsilane groups to be hydrophobic, thus allowing clear phase separation at the end-junction of the microchannel. The enzyme (laccase), which is surface active, was solubilized in a succinic aqueous buffer and the substrate (p-chlorophenol) was in isooctane. The degradation of p-chlorophenol occurred mainly at the aqueous-organic interface in the microchannel. We investigated the effects of flow velocity and microchannel shape on the enzymatic degradation of p-chlorophenol. Assuming that diffusion of the substrate (p-chlorophenol) is the rate-limiting step in the enzymatic degradation of p-chlorophenol in the microchannel, we proposed a simple theoretical model for the degradation in the microchannel. The calculated degradation values agreed well with the experimental data.

Algorithms↗

PubMed2003

Ionic liquids as a novel solvent for lanthanide extraction.

Octyl(phenyl)-N,N-diisobutylcarbamoylmethyl phosphine oxide (CMPO) dissolved in an ionic liquids, 1-butyl-3-methyl-imidazolium hexafluorophosphate, greatly enhances extractability and selectivity of lanthanide cations compared to that dissolved in conventional organic solvents; further, the recovery of lanthanides extracted into ionic liquids can be accomplished using several stripping solutions containing complexing agents. The possibility of utilizing ionic liquids as novel separation media in an industrial liquid-liquid extraction process was demonstrated.

Journal Article↗