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New Australian thraustochytrids: A renewable source of Biofuels, Omega-­‐3 oils and other bioproducts

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Chang, KJL (2013) New Australian thraustochytrids: A renewable source of Biofuels, Omega-­‐3 oils and other bioproducts. PhD thesis, University of Tasmania.

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Abstract

The
potential
of
biofuel
production
from
microalgae
is
of
intense
interest
globally
owing
to
growing
concern
with
rising
crude
oil
prices
and
future
availability.
In
addition
to
producing
lipids
for
potential
biofuel
application,
thraustochytrids
are
capable
of
forming
other
high-­‐value
bioproducts,
such
as
proteins,
enzymes,
omega-­‐3
polyunsaturated
fatty
acids
(PUFA),
carotenoid
pigments
and
exopolysaccharides
(EPS).
The
co-­‐production
of
high-­‐value
bioproducts
during
biofuel
production
is
desirable
when
it
adds
greater
value
to
the
production
process
and
improves
process
economics.
Thirty-­‐six
new
thraustochytrids
have
been
isolated
from
the
southeast
coast
of
Tasmania
and
far
north
Queensland.
They
were
separated
into
eight
chemotaxonomic
groups
(A

H)
based
on
fatty
acid
and
sterol
composition,
with
the
groups
clustered
closely
with
four
different
genera
(Aurantiochytrium,
Schizochytrium,
Thraustochytrium
and
Ulkenia)
based
on
18S
rDNA
molecular
identification.
In
an
initial
screening
study,
some
strains
produced
>
60
%
docosahexaenoic
acid
(DHA)
under
unoptimized
culture
conditions.
Aurantiochytrium
sp.
strains
(groups
G
and
H)
contained
15:0
(pentadecanoic
acid)
at
between
20

30
%
of
the
total
fatty
acids
(TFA)
and
16:0
(palmitic
acid)
in
the
range
of
7

15
%
TFA,
suggesting
these
strains
could
be
potential
candidates
for
biodiesel
production.
β,β-­‐Carotene,
canthaxanthin
and
astaxanthin
were
identified
in
pigmented
strains.
Part
of
the
process
to
scale
up
is
to
select
the
best
performing
strain
based
on
growth
and
biochemical
characteristics.
In
the
subsequent
trials,
eight
thraustochytrid
strains
from
the
different
chemotaxonomic
groups
(A

H)
were
compared
in
1
L
scale
baffled
shake
flasks
for
the
synthesis
of
EPS,
in
addition
to
biomass
yield
and
fatty
acid
profiles.
The
crude
chemical
characterization
of
the
EPS,
which
were
released
into
the
culture
media
by
these
strains,
was
performed
as
an
initial
step
in determining
the
potential
for
biotechnological
application
of
these
biomaterials.
Aurantiochytrium
sp.
strain
TC
20
had
the
highest
biomass
production
(18.5
g/L)
and
oil
yield
(7.5
g/L)
after
9
days
of
growth
in
4
%
w/v
glucose
basal
media
at
20
°C,
with
0.18
g/L
EPS
extracted
from
the
supernatant.
The
maximum
yield
of
EPS
was
observed
in
Schizochytrium
sp.
strain
TC
02
(0.3
g/L).
High
biomass
producing
strains
that
also
had
high
lipid
and
high
EPS
yield
may
be
better
candidates
for
commercial
production
of
biofuels
and
other
bioproducts.
The
next
phase
was
to
optimize
biomass
in
2
L
bioreactors.
The
growth
of
Aurantiochytrium
sp.
TC
20
was
also
investigated
using
glycerol
as
a
carbon
source.
Glycerol
is
becoming
increasingly
available,
because
it
is
a
by-­‐product
of
biofuel
production
from
vegetable
oil
and
animal
fats.
Fortification
of
the
feed
with
additional
nutrients
improved
the
biomass
yield
from
56
g/L
(34
%
total
fatty
acids)
to
71
g/L
(52
%
total
fatty
acids,
cell
dry
weight)
at
69
h.
A
life-­‐cycle
assessment,
from
the
upstream
biomass
production
to
the
direct
emission
of
biodiesel
combustion,
was
applied
to
assess
the
energy
balance
and
the
potential
environmental
impacts
of
this
heterotrophic
microalgal-­‐derived
biodiesel.
The
scenario
analysis
of
a
virtual
production
facility,
modeled
on
experimental
yield
data,
demonstrated
that
cultivation
of
heterotrophic
microalgae
for
the
production
of
biodiesel
is
comparable
in
terms
of
greenhouse
gas
emissions
and
energy
usage
to
production
of
petroleum
diesel.
The
LCA
identified
that
improvements
in
cultivation
conditions,
in
particular
the
bioreactor
energy
inputs
and
microalgae
yield,
will
be
critical
in
developing
a
sustainable
production
system.
This
study
demonstrates
the
potential
of
heterotrophic
cultivation
of
newly
isolated
endemic
thraustochytrids
to
provide
Australia’s
transportation
fleet
with
a
secure,
environmentally
sustainable
alternative
fuel
feedstock,
and
co-­‐production
of
high
value
bioproducts
that
can
provide
additional
revenue
to
benefit
the
economics
of
biofuel
production.

Item Type: Thesis (PhD)
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Date Deposited: 04 May 2014 23:07
Last Modified: 15 Sep 2017 01:06
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