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Lactic
Acid
Fermentations |
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Lactic
Acid
Fermentations -
This
is
one
of
the
oldest
and
simplest
fermentations
known
and
is
important
in
the
souring
of
milk.
In
this
fermentation,
a
NAD
linked
lactic
dehydrogenase
reduces
pyruvate
to
lactate
quantitatively.
Since
2
moles
ATP
are
consumed
in
the
formation
of
a
hexose
diphosphate
from
glucose
and
4
moles
of
ATP
are
subsequent
produced,
the
net
yield
is
2
moles
of
ATP
per
mole
of
hexose.
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Many
lactic
bacteria
such
as
Lactobacillus
casei,
Streptococcus
cremoris
etc,
carry
out
lactic
fermentations
in
which
lactic
acid
is
the
only
end
Product.
Some
other
members
of
the
lactic
group
carry
nut
a
heterolactic
fermentation
in
which
only
half
of
the
glucose
is
converted
into
lactate.
In
heterolactics,
glucose
is
fermented
through
phospho
ketolase
pathway
to
lactic
acid,
ethanol
and
CO2.
In
addition
to
these
two
fermentations,
a
variety
of
other
fermentations
have
been
identified
in
microorganisms
which
yield
different
products.
Here,
it
is
not
the
purpose
to
describe
them
in
detail
but
some
will
be
briefly
described.
In
all
these
fermentations,
the
glycolytic
pathway
(glucose
pyruvic
acid)
is
common
and
pyruvate
is
the
key
intermediate
and
the
fate
of
pyruvate
in
these
various
fermentations
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