Agriculture Reference
In-Depth Information
To characterize the degradation of brown seaweed polysaccharides by M. oxydans ,
experiments were performed in a 1000 ml flask (with a 250 ml working volume). The culture
medium that was used for the degradation experiment was the same medium that was used for
the culture in tubes, as described above. The previously harvested cells were proliferated for 9
h under the same culture conditions and used as an inoculum (0.5%, w v -1 ) for this
experiment. After inoculation, the flask was incubated in a rotary shaking incubator at 30 °C
and 180 rpm for 5 d.
In each biodegradation experiment, samples were periodically taken from each flask to
measure the changes in pH, cell density and in the concentration of reducing sugars. The
samples were also analyzed to examine the concentrations of COD Cr , TN, cations and anions.
Seed Germination Test
The phytotoxicity of the biodegraded culture broths of seaweeds was evaluated by a seed
germination test according to the method of Wong et al. (2001). Ten milliliters of each culture
broth was filtered through a 0.45-µm membrane filter after centrifugation at 8000 rpm for 10
min. In parallel, 10 ml of the culture broth containing cells was also tested. For measurements
of seed germination and root length, 5 ml of the filtrate or of the original culture broth at
various dilution ratios was pipetted into a sterile Petri dish that was lined with Whatman #1
filter paper. Ten cress ( Lepidium sativum ) seeds were placed evenly in each Petri dish and
incubated at 25 ºC in the dark at 75% humidity. After 72-h incubation, the seed germination
and root length in each Petri dish were measured against the control using distilled water. The
percentages of relative seed germination (RSG), relative root growth (RRG), and germination
index (GI) were estimated according to the following formula (Hoekstra et al., 2002):
Number of seeds germinated in the culture broth
RSG (%) =
× 100
Number of seeds germinated in the control
Mean root length in the culture broth
RRG (%) =
× 100
Mean root length in the control
RSG × RRG
GI (%) =
100
Hydroponic Culture
Kidney bean and barley were selected as reference plants and cultivated in a mini-
hydroponic culture pot (5×12×8 cm 3 ) against the control to evaluate the fertilizing ability of
the biodegraded culture broths of seaweeds. For the hydroponic cultures, each culture broth at
maximal degradation and its mixture were used, and a commercial seaweed fertilizer, which
sold at a moderate price in Korea, was tested for relative evaluation by comparison. The
mixed culture broths of seaweeds and fish (mackerel) wastes were also tested. The
hydroponic culture pot was composed of a glass vessel and a plastic screen inside. In each
pot, 10 seeds of kidney bean or 20 seeds of barley were placed on top of the plastic screen.
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