Morio Hirano

Removal of nitrate, nitrite, ammonium and phosphate ions from water by the aerial microalga Trentepohlia aurea

The aerial microalga Trentepohlia aurea has beeninvestigated in relation to removal characteristics of nitrate, nitrite,ammonium and phosphate ions. When the alga was cultured in medium with veryhighconcentrations of ammonium, nitrate and phosphate ions, it showed relativelyhigh growth and removal rates. It also grew quite well with high nitriteconcentration (< 141 mg NO2-N L−1).The removal rate was 0.28 mg NO2-N L−1day−1 in the 40-day culture, when it was cultured in modifiedBolds basal medium with added 51 mg NO2-NL−1. In addition, we examined simultaneous removal of nutrientions. The biomass was 1.5 times higher in medium which N- and P-sourcesufficient than in ordinary medium. Higher removal ratios of nitrite andnitratefrom medium were shown in a 30-day culture, reaching 37% and 32%, respectively.It is concluded that T. aurea has the potential for use inthe purification of wastewater.

Magnetic field effects on photosynthesis and growth of the cyanobacterium Spirulina platensis

We investigated the influence of a magnetic field on photosynthesis in, and the growth of Spirulina platensis (S. platensis), under magnetic fields with magnetic flux densities varying from 0.5 gauss (geomagnetic field) to 700 gauss. The specific growth rate of S. platensis was the highest at 100 gauss, being 1.5-fold that at 0.5 gauss, while the growth was obviously inhibited at 700 gauss. The existence of a magnetic field had no effect on the growth when S. platensis was cultured in the dark on a medium containing 0.3% glucose. The oxygen evolution rate during photosynthesis increased with increase in magnetic flux density, and the intracellular concentrations of sugar and phycocyanin, a light-harvesting pigment present in the thylakoid membrane in which reactions of the photosynthetic electron transfer system occur, reached maximal values at 100 gauss. At magnetic flux densities of a over 100 gauss, the phycocyanin content decreased with increase in magnetic flux density. The content of glyceroglycolipid, which exists exclusively in the thylakoid membrane, decreased with increase in magnetic flux density, especially so at 700 gauss, when it became 44% that at 0.5 gauss. From the aforementioned results, it is evident that magnetic fields accelerate the growth of S. platensis associated with activation of light excitation in the photosynthetic electron transfer system and increase in phycocyanin contents, and that these effects are maximal at magnetic flux densities of around 100 gauss. Nevertheless, when a magnetic flux density of over 400 gauss was applied, growth inhibition was observed with decrease in the phycocyanin content, and production of chemical energy necessary for sugar synthesis.

Simultaneous production of β-carotene, vitamin E and vitamin C by the aerial microalga Trentepohlia aurea

The biomass production and antioxidant accumulation of the aerial microalga Trentepohlia aurea were examined. Using ammonium chloride as nitrogen source for growth in liquid medium, the growth rate was exponential and accompanied by a marked fall in the pH of the medium. The highest growth rate of 152 mg L-1 day-1 (logarithmic phase) was attained when T. aurea was cultured with aeration of 5% CO2-enriched air in medium buffered with HEPES. The growth rate and antioxidant content were enhanced under 5% CO2 by switching the light intensity from 43 to 143 μmol photon m-2 s-1 for the two-stage culture. As a result, T. aurea cells accumulated 2.1 mg β-carotene, 0.3 mg L-ascorbic acid and 2.4 mg tocopherols, respectively, per g dry cell. The simultaneous production of useful materials, such as β-carotene, vitamin E and vitamin C, was demonstrated.

Removal of inorganic nitrogen sources from water by the algal biofilm of the aerial microalga Trentepohlia aurea

Removal of inorganic nitrogen sources by cells of the aerial microalga Trentepohlia aurea grown on the surface of substrate, such as filter paper, has been investigated in a batch system. When the alga grew on the paper dampened with medium, it actively ingested inorganic nitrogenous compounds in the medium. Immobilized cells on the filter papers were called ‘algal biofilm’ in this study. When the algal biofilms were soaked in modified Bolds Basal medium (using 1 g NH4Cl l−1 as a N source), the removal rate was 4.25 mg ammonium-N l−1 day−1 in 40 days. In modified medium with added 26 mg nitrite-N, the removal rate of the total inorganic N ion by the biofilms reached 5.11 mg N l−1 day−1. This removal rate of total N ion was higher than that in the medium by addition of 26 mg nitrate-N. In addition, we tried to examine simultaneous removal of ammonium, nitrate, and nitrite ions and growth inhibition of cyanobacteria in the medium by using the algal biofilms. Consequently, it was demonstrated that the algal biofilms of T. aurea could be utilized as a biofunctional material for the purification of wastewater.

Development of laboratory-scale photobioreactor for water purification by use of a biofilter composed of the aerial microalga Trentepohlia aurea (Chlorophyta)

Biofilms formed by the green alga Trentepohlia aurea could be a useful tool in the removal of nitrate and phosphate from water. When a prepared biofilter was dampened with medium and incubated under low light intensity (10xa0μmol photons m−2 s−1) between 5 and 50xa0μmol photons m−2 s−1, the efficiency of removal of inorganic compounds from water was higher without the decomposition of chlorophylls in the cells. Algal cells immobilized on a glass fiber filter could be kept for 12xa0weeks under dark conditions at 4°C in the refrigerator. We tried to construct a laboratory-scale photobioreactor for the removal of inorganic nitrogen and phosphate from water by the biofilm. In this study, the synthetic wastewater was prepared by diluting 18-fold Bold’s basal medium with deionized water. The photobioreactor could efficiently remove nitrate and phosphate from the synthetic wastewater under continuous illumination. The removal ability of nitrate and phosphate per sheet of the biofilter in the photobioreactor exhibited about an 8- and 16-fold increase, respectively, in 3 days, compared with the bath experimental results. This study showed that the cycling of wastewater in the reactor by the pump led to a significant improvement in the efficiency of the inorganic ion uptake from water.

Characteristics of chlorophyll formation of the aerial microalga Coelastrella striolata var. multistriata and its application for environmental biomonitoring

The growth and ammonium uptake of the aerial microalga Coelastrella striolata var. multistriata, which was isolated from the surface of rocks, were characterized in this study. The specific growth rate of the alga was mu=0.3 d(-1), as calculated in the growth logarithmic phase. The algal cells were able to remove almost 100% of the ammonium ions from medium in 5 d, with the removal rate of ammonium-N being 0.4 mg/l/h. It was shown that the alga has a unique ability to be a reddish orange to green color depending on the nitrogen source concentration in the medium. Astaxanthin, adonixanthin, canthaxanthin, and beta-carotene were found in the reddish orange cells of the alga. The assessment of water pollution was attempted using this aerial microalga. When the reddish orange alga was incubated in the experimental medium with added ammonium-, nitrate-, or urea-N as a nitrogen source, an approximately linear relationship existed between the nitrogen concentration and chlorophyll formation. Using the chlorophyll formation of the alga, for example, it was possible to estimate spectrophotometrically the total nitrogen content in water collected from aquatic systems. Biofunctional materials for environmental biomonitoring using photosynthetic microorganisms are called green devices in this study.

Polyunsaturated fatty acid production by Ribes rubrum calli

Abstract Methods of polyunsaturated fatty acid (PUFA) production by plant tissue culture techniques were investigated. Ribes rubrum calli were induced from leaves, and the highest rates of callus induction and proliferation were observed in B5 modified medium supplemented with 4.0 mg/ l 1-naphthalene acetic acid (NAA) and 2.0 mg/ l 6-benzyl amino purine (BAP). PUFA accounted for 53.8% (w/w) of the total higher fatty acid content in the calli obtained at a culture temperature of 25°C and 59.7% in these obtained at a culture temperature of 10°C. It was demonstrated that fats and oils with a high PUFA content were produced efficiently by the low-temperature treatment.

Characterization of Ribes rubrum callus cultured under low temperature.

Ribes rubrum callus was cultured at the temperature of 15 degrees C for 28 d. The contents of proteins and lipids in the callus cultured at 15 degrees C in a 28 d culture was significantly increased, being 1.1- and 1.2-fold, respectively, of those in callus cultured at 25 degrees C. Comparisons of the contents of monogalactosyldiacylglycerol (MGDG), digalactosyldiacylglycerol (DGDG), sulfoquinovosyldiacylglycerol (SQDG) and phosphatidyldiacylglycerol (PG) revealed that in the callus cultured at 25 degrees C, the content of MGDG was significantly decreased and those of the others significantly increased compared to those in callus cultured at 15 degrees C, in a 7 d culture. But, in a 28 d culture, the contents of these lipids in callus at 15 degrees C became the same as those in callus cultured at 25 degrees C. In regard to the protein composition, the contents of proteins 30 KDa or less in callus cultured at 15 degrees C in a 28 d culture were significantly higher than those in callus cultured at 25 degrees C. These consequences reflect that not only increase in the polyunsaturated fatty acid (PUFA) ratio of total fatty acid (TFA) with cold treatment reported by us previously [Hirano, M., J. Ferment. Bioeng., 83, 608-611 (1997)], but also an increase in low-molecular-weight protein content might be responsible for the cold-tolerance of R. rubrum callus.