Assay of nitrogen sources in water by the green device
The concentration of nitrogen sources in the water of River
Keihin-unga, River Nomi, and River Meguro (flowing into
Tokyo bay) could be estimated using the green device, for
example, and changes in the color of the cell suspension discriminated
with color sheets as shown in Fig. 9 (nitrogensource concentration: estimated to be from 5 to 10 mg/l).
Biotests of the total nitrogen content in water collected from
a lake, canal, and river were spectrophotometrically carried
out using the chlorophyll formation of the green device (see
Table 2). After filtration of the collected water, the pH was
adjusted to 7.5 with 30 mM HEPES and HCl or NaOH. The
suspended cells in the collected water were shaken reciprocally
in a disposable absorption cell with a shaker for 48 h at
40 mol photons/m
2
/s and 25C. The algal regreening presented
in this study was carried out in water without the addition
of trace elements (Mg, Fe ions, etc.) as nutrients. The
total nitrogen contents assayed by the green device were estimated
from the relationship between the ammonium-N
concentration and the chlorophyll formation in Fig. 6a. The
total nitrogen contents obtained by the green device seem
to be approximately similar, although the values were somewhat
higher than those obtained using the Japanese industrial
standard method.
Thus, the growth and ammonium uptake of the aerial microalga
C. striolata var. multistriata, which was isolated
from the surface of rocks, were characterized in this study.
In addition, we showed that the assessment of water pollution
could be readily conducted using the algal cells, whichhave a unique ability to be a reddish orange to green color
depending on the nitrogen source concentration in the culture
medium. This biofunctional material for environmental
biomonitoring and remediation using photosynthetic micro-organisms was called a green device.