Agriculture Reference
In-Depth Information
Figure 4. TLC of the degradation products in the biodegraded culture broth of red seaweed. M1-M3
indicates standard markers. Lane 1, day 0; lane 2, day 1; lane 3, day 2; lane 4, day 4; and lane 5, day 5
of cultivation.
Brown Seaweed
A time course monitoring the degradation of brown seaweed polysaccharides by M.
oxydans is shown in Figure 5. As shown in Figure 5A, the pH steadily decreased from 6.09 to
4.20 after 5 d as the biodegradation proceeded. The cell number increased from 4.5×10 6 CFU
ml -1 to 1.6×10 7 CFU ml -1 after 2 d, and then was almost maintained until the end. The
concentration of reducing sugar was 0.18 g l -1 and steadily increased to 0.35 g l -1 after 5 d.
The small amount of reducing sugars that were present at the beginning of biodegradation
was due to the Laminaria powder pretreatment to improve its solubility. The production of
alginolytic enzymes has been shown to improve in the presence of glucose and peptone
(Alekseeva et al., 2004). Most likely, M. oxydans utilized this reducing sugar, resulting in the
active biodegradation of brown seaweed polysaccharides at approximately 3 d. Based on the
changes in pH, cell number, and in the concentration of reducing sugars, the 4-d culture broth
was selected, and its fertilizing ability was later tested.
Figure 5B and Figure 5C present the changes in the concentrations of cations and anions
during the degradation of brown seaweed polysaccharides. As shown in Figure 5B, the
concentration of Na + slightly decreased from 1322.0 to 1301.0 mg l -1 , whereas the
concentration of NH 4 + slightly decreased from 109.0 to 98.5 mg l -1 . During biodegradation,
the concentrations of Cl - , NO 3 - and PO 4 3- slightly decreased, whereas the concentration of
NO 2 - was almost maintained.
The average removal percentages of COD Cr and TN were 21.4 and 5.0%, respectively
(Figure 5D). The COD Cr /TN ratio decreased from 28.8 to 23.8 in the end under a relatively
stable C/N ratio. This high C/N ratio was dependent on the microbial characteristics.
As brown seaweed polysaccharides were degraded by M. oxydans over time, TLC
revealed the migration of degraded oligosaccharides with different DP (Figure 6). It was
clearly observed that a glucose band appeared after 3 d culture, supporting the idea that the M.
oxydans strain degraded brown seaweed polysaccharides in an exolytic manner. Alginate
oligosaccharides have been reported to promote the germination and shoot elongation of
Search WWH ::




Custom Search