ACHIEVEMENT OF ZERO EMISSIONS BY THE BIOCONVERSION OF FISHERY WASTES INTO FERTILIZER - Fertilizers: Components, Uses in Agriculture and Environmental Impacts - page 78

The drop in the concentration of reducing sugars was due to consumption by the cells. It
was reported that glucose could significantly induce cellulase (Dhillon et al., 1985). After the
B. licheniformis TK3-Y strain utilized the monosaccharide, the active biodegradation of green
seaweed polysaccharides could occur after 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 1B and Figure 1C present the changes in the concentrations of cations and anions
during the biodegradation of green seaweed polysaccharides. As shown in Figure 1B, the
concentration of Na + steadily decreased from 2342.1 to 1002.2 mg l -1 , whereas the
concentration of NH 4 + increased from 1243.6 to 2231.7 mg l -1 . During biodegradation, the
concentrations of Cl - and NO 2 - increased, whereas the concentrations of PO 4 3- and NO 3 -
decreased due to their partial utilization by cells (Yamamoto et al., 2005). The convergence of
these changes was accomplished at approximately 3 d of culturing. The increase in the
concentrations of Cl - and NO 2 - was most likely due to the decrease in Na + and to the
conversion of NH 4 + , respectively. The high content of NaCl in the seaweed digestate causes
its ineligibility for use as fertilizer (Cecchi et al., 1996). It is recommended that a low level of
NaCl be contained in the biodegraded culture broth of seaweed for commercial use.
The average removal percentages of COD Cr and TN were 42.9 and 19.9%, respectively
(Figure 1D). The COD Cr /TN ratio decreased from 7.3 to 5.2 in the end such that the microbial
degradation occurred under a relatively stable C/N ratio. The C/N ratio was low compared
with that (10.5-13.1) achieved in seaweed composting (Tang et al., 2011).
As green seaweed polysaccharides were degraded by B. licheniformis TK3-Y over time,
TLC revealed the migration of degraded oligosaccharides with different degrees of
polymerization (DP) (Figure 2). Although the bands of DP 1-3 that were produced by the
Ulva powder pretreatment were observed at the beginning of the experiments, these bands
weakened over time in the culture.
Figure 2. TLC of the degradation products in the biodegraded culture broth of green seaweed. M1-M3
indicates standard markers. Lane 1, day 0; lane 2, day 1; lane 3, day 2; lane 4, day 3; lane 5, day 4; and
lane 6, day 5 of cultivation.