Agriculture Reference
In-Depth Information
ability of water soluble nitrogen due to the action of proteases. The sharp decline in
urease activity may be due to the accumulation of nitrates in composting mixture.
Cayuela et al. (
2008
) reported very low urease activity during the entire duration of
semi-solid olive mill waste composting, which was attributed to the low concentra-
tion of nitrogen and also to the low levels of available substrates released during
mineralization. Liu et al. (
2011
) reported the presence of significant urease activity
during the second week of composting of daily manure with rice chaff. Correlation
analysis indicated a strong correlation with water soluble nitrogen and ammonium
ions. A similar result was also reported by Garcia et al. (
1995
), wherein an increase
in urease activity was directly correlated to the availability of water soluble nitro-
gen. Dehydrogenase activity is used as measure of overall microbial activity and
reflects the amount of microbial biomass involved in the process of respiration and
metabolic processing (Castaldi et al.
2008
). Phosphatase activity has been reported
during the early phase of composting followed by decline in activity (Raut et al.
2008
); however, Ros et al. (
2006
) reported an increase in alkaline phosphatase ac-
tivity during the beginning of composting, reaching a maximum by the end of the
process. Phosphatase activity could be related to the amount and availability of
organic phosphate compounds present in the composting mixture. This enzyme has
high agronomic value because it hydrolyses compounds of organic phosphorous
and transforms them into different forms of inorganic phosphorus which is assimi-
lated by plants. The phosphatase enzyme is also considered a general microbial
indicator (Raut et al.
2008
). Phosphatase is a key enzyme in the phosphorus cycle
and is induced by the presence of carbohydrate derived structures that are degraded
to glucose by enzymatic action. This enzyme is only synthesized by microbes, and
is not released by plants and/or organic matter residues Alkaline phosphatase is thus
a relevant enzyme for characterization of the composting process (Raut et al.
2008
;
Fig.
6.1
).
6.7
Cellulolytic Thermophilic
Bacilli
and Cellulases
from Compost
Amore et al. (
2013
) reported the isolation of novel cellulolytic bacterial strains from
industrial waste based compost. The potent bacterial strains were identified as
B.
licheniformis
strain 1,
B. subtilis
subsp.
subtilis
strain B7B,
B. subtilis
subsp.
spizizenii
strain 6 and
B. amyloliquefaciens
strain B13C.
B. amyloliquefaciens
strain
B13C was found to be thermotolerant as growth was observed in the range of 28-
47 °C. The enzyme was purified to homogeneity and SDS-PAGE indicated the pres-
ence of a 55.0 kDa protein. LC-MS analysis of the proteome corresponded to the
presence of a peptide belonging to the GH5 family of endoglucanases. The endo-
glucanase exhibited broad temperature optima (50-70 °C) and retained 90 % activ-
ity following 144 h incubation at 40 °C. The kinetic parameters including
K
m
(9.95 mg/ml) and V
max
(284 μmol/min) were determined for the purified enzyme.
Acharya et al. (
2012
) reported the isolation of 10 thermophilic and 15 thermotoler-
