Biomedical subjects

Tomohisa Katsuda

Publications and source records attributed to Tomohisa Katsuda.

10 recordsLinked to original sources

PubMed2006

Single nucleotide polymorphism detection method by temperature-gradient affinity chromatography using a single-stranded oligo-DNA coupled column.

We developed an affinity chromatographic method for simple single nucleotide polymorphism (SNP) detection by use of a single-stranded DNA-coupled column and temperature gradient elution, utilizing the difference in thermal stability between hybridized double-stranded DNAs with and without mismatched base-pairs in the course of temperature gradient elution. We studied experimentally and theoretically the elution behavior of DNAs with and without SNPs in this chromatography and proposed a numerical calculation method based on a thermodynamic dissociation model. The effects of the column volume, flow rate of eluent and heating rate of the column on elution profiles were clarified. For designing DNA ligands, mismatched base-pair positions favorable for detection of SNPs were also explored by use of hybridized DNAs coding a part of the human TP53 gene.

Base Pair Mismatch↗

PubMed2006

Degradation of cyanuric acid in soil by Pseudomonas sp. NRRL B-12227 using bioremediation with self-immobilization system.

The rates of degradation of cyanuric acid, a key intermediate in a metabolic pathway of s-triazine herbicides, were measured for Pseudomonas sp. NRRL B-12227. The rate of degradation was affected by the rate of cyanuric acid transport through cell membranes and the activity of cyanuric acid amidohydrolase inside the cells. At low concentrations of cyanuric acid, the acclimation of cells to cyanuric acid and/or added nutrients effectively enhanced the degradation rate. The strain was also applied to bioremediation using a Bioremediation with Self-Immobilization System (BSIS), in which Pseudomonas sp. NRRL B-12227 cells were co-immobilized with Bacillus subtilis, the latter of which secretes a viscous polymer, in a shallow layer of soil packed in a column. More than 70% of the Pseudomonas sp. NRRL B-12227 cells were co-immobilized with the B. subtilis in a 7.5 cm layer of the packed soil by self-aggregation. More than 60% of the 1 mM cyanuric acid supplied to the packed soil was degraded in this layer during a 72 h period.

Biodegradation, Environmental↗

PubMed2006

New detection method for hydrogen gas for screening hydrogen-producing microorganisms using water-soluble wilkinson's catalyst derivative.

A water-soluble color indicator was developed for the effective screening of hydrogen-producing microorganisms. This indicator consists of a coloring agent and a water-soluble derivative of Wilkinson's catalyst. Wilkinson's catalyst, Tris(triphenylphosphine) rhodium chloride, had been developed as a catalyst for the hydrogenation of olefins. We used a sulfonate of the catalyst for the hydrogenation of coloring agent in an aqueous medium. Several coloring agents, such as methyl orange, methyl red sodium, neutral red and Evan's blue, dissolved in water together with the sulfonated catalyst showed a change in color when hydrogen gas was fed into the solution by sparging at room temperature. We confirmed that methyl orange was decolorized by biologically produced hydrogen, when the photosynthetic bacterial strain Rhodobacter capsulatus ST-410 was grown in a medium containing 0.6 mM catalyst and 0.075 mM methyl orange in test tubes of 5 ml working volume.

Catalysis↗

PubMed2006

Effect of flashing light from blue light emitting diodes on cell growth and astaxanthin production of Haematococcus pluvialis.

To conserve energy in the production of astaxanthin by the green alga Haematococcus pluvialis, we utilized intermittent flashing light from blue light emitting diodes (LEDs) and investigated the effects of the incident light intensity (2-12 micromol m(-2) s(-1)), duty cycle (17-67%) and frequency (25-200 Hz) of flashing on the cell growth and astaxanthin production. In the above ranges, the final astaxanthin concentration under illumination by flashing light was significantly higher than that obtained under illumination with continuous light at the same incident intensity. For example, flashing light at an incident intensity of 8 micromol m(-2) s(-1) gave the same final astaxanthin concentration that was obtained under continuous light illumination at 12 micromol m(-2) s(-1), thus reducing energy consumption by 1/3. We therefore conclude that flashing light from blue LEDs is a promising illumination method for indoor algal cultivation using photobioreactors.

Bioreactors↗

PubMed2006

Effective utilization of transmitted light for astaxanthin production by Haematococcus pluvialis.

A new cultivation method, in which physiological responses of Haematococcus pluvialis to different intensities and wavelengths of illuminating light are utilized, is proposed. In this method, light transmitted through a cultivation vessel illuminated from the opposite side was utilized for the early-phase cultivation of H. pluvialis in another inoculated vessel that was located behind the cultivation vessel, to save time required for the growth of cells. After harvesting cells from the front vessel, the vessel that was originally behind was shifted to the position of the front vessel. The abrupt increase in light intensity caused by shift of the position induced the effective accumulation of astaxanthin. These procedures for inoculation, shift of vessels and harvest were repeated using two vessels arranged in series along the light path. After four repeated cycles of cultivation (840 h from the start of cultivation), using 2.5 cm thick vessels, astaxanthin production per unit volume and the astaxanthin content were higher than obtained in a batch cultivation with two 2.5 cm vessels.

Bioreactors↗

PubMed2005

Fed-batch culture under illumination with blue light emitting diodes (LEDs) for astaxanthin production by Haematococcus pluvialis.

To increase the cell concentration and the accumulation of astaxanthin, the effects of the fed-batch addition of 10-fold-concentrated medium to supply nutrients, as well as illumination with blue light emitting diodes (LEDs), on cell growth and accumulation of astaxanthin were studied for the cultivation of Haematococcus pluvialis. Using the fed-batch addition method, the cell concentration increased above 1 mg-dry cell/cm3, and under illumination with blue LEDs, the astaxanthin concentration reached approximately 70 microg/cm3. This method was much simpler to operate than the medium replacement method in operation and enabled us to attain a higher total yield of astaxanthin.

Biotechnology↗

PubMed2005

Improvement of growth stability of photosynthetic bacterium Rhodobacter capsulatus.

Using a semicontinuous culture method, in which operational parameters such as cell concentration and light intensity distribution were maintained almost constant, instability of the specific growth rate of Rhodobacter capsulatus B-100, a purple bacterium, was observed to be similar to that of R. capsulatus ST-410 when cultivated under high ratios of light intensity on the illuminated side to that of the transmitted light. Such instability was not observed in the cultivation of Chlorella vulgaris, a eukaryotic green alga, even at higher cell concentrations. Under the same conditions, the increase in only the ferrous concentration from 43 microM, the concentration in the original RCV medium, to 172 microM sustained a stable growth, whereas Fe(2+) was slightly consumed during the cultivation. Supplemental illumination with a fluorescent lamp on the transmitted side of a flat plate photobioreactor sustained a moderate level of stable growth, while a halogen lamp slightly affected the growth stability. Our results showed that an increase in Fe(2+) concentration or supplemental illumination improves the growth stability of R. capsulatus.

Bioreactors↗

PubMed2004

Characteristics of neutralization of acids by newly isolated fungal cells.

Soil microorganisms play an important role in maintaining soil pH at levels suitable for other soil organisms. To clarify the biological neutralization mechanism in soil, we isolated soil microorganisms showing a high ability to neutralize acids and studied their characteristics. From our taxonomic study, three isolated strains were identified as filamentous fungi, namely Mucor sp., Aspergillus fumigatus, and Aureobasidium pullulans. These strains could secrete basic materials, such as ammonia, for neutralization, grow in the medium at pH 4.0 and increase the pH of the medium to approximately 8.0. These microbial cells could neutralize not only nitric acid but also sulfuric and hydrochloric acids. The strains could also grow by utilizing nitric acid as a sole nitrogen source. In the soil containing these organisms, the pH was maintained in the neutral range by the buffering action of basic materials that they secrete. These results suggest that these fungal cells are useful for protecting the soil from acidification by acid rain.

Journal Article↗

PubMed2004

Effects of nutrient supply methods and illumination with blue light emitting diodes (LEDs) on astaxanthin production by Haematococcus pluvialis.

In order to increase the cell concentration and the accumulation of astaxanthin, the effects of nutrient concentration, pH, illumination and methods of supplying nutrients were studied for the cultivation of Haematococcus pluvialis. The replacement of media to avoid the deficiency of nutrients increased the cell concentration above 1 mg-dry cell cm(-3) without induction of astaxanthin accumulation. Illumination with blue light emitting diode lamps and nutrient starvation induced accumulation of astaxanthin, and the interactive effects of these two increased the astaxanthin concentration to 76 mug cm(-3).

Journal Article↗

PubMedDate not supplied

Effects of light intensity distribution on growth of Rhodobacter capsulatus.

For cultivation of photosynthetic cells under defined light intensity distributions, the repeated batch culture, in which a part of culture broth containing grown cells was repeatedly replaced at predetermined time intervals with a fresh medium to keep the cell concentration constant at an initial value, was employed. By use of this method the effects of the light intensity distribution on the growth characteristics of Rhodobacter capsulatus were studied. Unexpected decreases in the specific growth rate were observed in culture of R. capsulatus at high cell concentrations and a long light path length. Big differences in the light intensities of lightly and darkly illuminated portions in photobioreactors, which reflects the light intensity distribution, seemed to cause this phenomenon, which must be taken into consideration for stable growth of photosynthetic cells.

Adaptation, Physiological↗