Environmental Engineering Reference
In-Depth Information
7.1 Introduction
the sites of intensive livestock production. This
excessive P in soil runs off under different cli-
matic cycles to different water sources such as
ponds and rivers causing rapid growth of phy-
toplanktons, algae, creating dense population
of cyanobacterial blooms, hypoxia and death of
marine animals. These blooms also make plants
unable to photosynthesise and produce food for
their survival (Vats and Banerjee
2005
).
Adopting a suitable approach for phytic acid
P hydrolysis may lead to decreased environmen-
tal pollution and feed cost. Several interventions
have been suggested for phytic acid hydrolysis
comprising physical methods, e.g. autoclaving,
cooking; and chemical methods, e.g. ion exchange
and acid hydrolysis, but reported to compromise
the nutritional value of the food (Singh et al.
2011
). Therefore as an alternative, enzymatic hy-
drolysis is preferred for the reduction of phytic
acid content in food and feed in several studies
(Vohra and Satyanarayana
2003
; Vats and Baner-
jee
2004
; Greiner and Konietzny
2006
; Rao et al.
2009
; Singh and Satyanarayana
2011
; Singh et al.
2011
; Kumar et al.
2014
). These studies showed
considerable interest of food and feed industries
towards phytate-degrading enzymes, mainly phy-
tases (myo-inositol hexakisphosphate phospho-
hydrolase), which catalyse the hydrolysis of the
phosphate moieties in phytic acid (Fig.
7.1
). Since
Phosphorus (P) is a macronutrient for plants
and plays important roles in the biosynthesis of
nucleic acids, cell membranes and regulation
of many enzymes. It is available in soil either
as inorganic or organic fractions in significant
amounts and not readily accessible to plants,
leading to P deficiency in soil as a major problem
for agricultural production. The major storage
form of organic P in soil is phytate (salts of phytic
acid), which is not readily provide P to plants be-
cause of its complex with cations or adsorption
to various soil components. This form of P is also
the principal storage form in plants. Phytic acid
P constitutes 1-5 % weight in cereals, legumes,
oils, seeds and nuts (Sapna et al.
2013
). The phy-
tate P is generally unavailable to monogastric
animals (chicken, swine, fish, humans) due to ei-
ther absence or insufficient secretion of enzymes
essential for phytate hydrolysis in digestive tract
(Kumar et al.
2014
). Consequently, P remains un-
absorbed in the digestive tract and gets excreted
along with faeces as such in the environment
leading to P pollution. To supplement P require-
ment, animal feeds are commonly supplemented
with inorganic P. Further, the excretion of undi-
gested phytate along with inorganic P imposes
global ecological problems of P eutrophication at
Fig. 7.1
Phytic acid hydrolysis by phytase enzyme
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