ACHIEVEMENT OF ZERO EMISSIONS BY THE BIOCONVERSION OF FISHERY WASTES INTO FERTILIZER - Fertilizers: Components, Uses in Agriculture and Environmental Impacts - page 85

This result suggested the possibility of seaweed culture broth as liquid fertilizer because
the1000-fold diluted liquid fertilizer could be used more often in horticulture for general
purposes. Similar to the culture broth of fish waste (Kim et al., 2010), there was no
phytotoxicity present in 1,000-fold-diluted culture broths of seaweeds.
The GI tests were also executed for the original culture broths of seaweeds containing
cells, and the results are presented in Figure 8. The GI values of all the seaweed culture broths
tended to increase with the presence of cells. It has been reported that phytotoxicity caused by
organic compounds can be remedied by aerobic decomposition (Wong et al., 2001), and in
particular, biofertilizers containing microorganisms can promote plant growth (Rokhzadi et
al ., 2008). For this reason, relatively better results may be observed with the culture broths of
seaweeds that contain polysaccharide-degrading bacteria.
Amino Acid Composition
The amino acid composition of the biodegraded culture broths of seaweeds was analyzed
because amino acids are an essential part of the active fraction of organic matter in a
fertilizer. The amino acid levels of the biodegraded culture broths are presented in Table 2.

Table 2. Amino acid composition of the biodegraded culture broths
(unit: g 100 g protein -1 )

Amino acid Green seaweed Red seaweed Brown seaweed

Lysine 3.22 0.70 0.06

Histidine 0.22 n.d. a n.d.

Arginine n.d. n.d. n.d.

Aspartic acid 0.05 0.06 0.06

Threonine n.d. n.d. n.d.

Serine n.d. n.d. n.d.

Glutamic acid n.d. n.d. 0.24

Proline n.d. n.d. 0.04

Glycine 0.03 0.07 0.06

Alanine n.d. n.d. 0.23

Valine 0.01 0.06 0.05

Cysteine n.d. 0.48 n.d.

Tryptophane n.d. n.d. n.d.

Methionine 0.78 0.46 n.d.

Leucine 0.12 n.d. 0.07

Tyrosine 1.49 n.d. 0.03

Isoleucine n.d. n.d. 0.03

Phenylalanine 2.6 n.d. 0.39

Glutamine 0.41 0.64 n.d.

Asparagine n.d. n.d. n.d.

Total 8.93 2.47 1.26

a n.d.: not detected.

Each culture broth contained essential amino acids in different proportions, and the levels
of arginine, threonine, serine, tryptophan and asparagines were not detected in all cases. The
levels of total amino acids in the culture broths of green, red and brown seaweeds were 8.93,
2.47 and 1.26 g 100 g protein -1 , respectively. The level of total amino acids in the culture