Synthesis of intracellular lipids by yeast cultivated in a medium ...

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20 Φεβ 2013 (πριν από 4 χρόνια και 1 μήνα)

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S
YNTHESIS OF INTRACEL
LULAR LIPIDS BY YEAS
T CULTIVATED IN A ME
DIUM
SUPPLEMENTED WITH WA
STE GLYCEROL


Katarzyna Stasiewicz,
Marek Adamczak
, Włodzimierz Bednarski

Department of Food Biotechnology, University of Warmia and Mazury
i
n Olsztyn,

J. Heweliusz St.

1, 10
-
718 Olsztyn, Poland, e
-
mail: marek.adamczak@uwm.edu.pl


The aim of the experiments was to evaluate waste glycerol uptake by selected fungi strains.

In the experiment
,

the following fungi strains were used:
Cryptococcus curvatus

2,
Cryptococcus curva
tus

10,
Yarrowia lipolytica

from
the
Department of Industrial and Food
Microbiology (University of Warmia and Mazury in Olsztyn, Poland),
Rhodosporidium
toruloides

DSM 4444 from German Collection of Microorganisms and Cell Cultures (DSMZ,
Braunschweig,
Germany). The strains were propagated on wort agar medium
and cultivated
in a mineral medium supplemented with different carbon sources
at 30 °C or 25 °C. The
cultivation was performed in
500 cm³ Erle
nmeyer fl
a
sks at 25 or 30 °C in
an
incubator shaker
at 2
50

rpm

for 24

h
.

During the cultivation, t
he following parameters were determined: concentration of total
biomass in the medium (X, g L
-
1
), concentration of lipid free biomass in the medium (X
f
, g L
-
1
), concentration of intracellular lipids in the medium
(L, g L
-
1
), lipid percentage in biomass
(Y
L/X
, %, w:w),
lipid
yield
per unit of

glycerol consumed (Y
L/S
, g of lipids synthesized per g
of glycerol), yield of lipid free biomass
per unit of

glycerol consumed (Y
Xf/S
, g g
-
1
), glycerol
consumed (Gly
U
, % of ini
tial amount of glycerol).

The initial experiments were performed in the medium supplemented with glucose or
different quality glycerol fraction at a concentration of 30 g L
-
1
. The highest amount of
intracellular lipids 3.6 and 1.3


3.1 g L
-
1

was synthesized by
C. curvatus

2 in the medium
with glucose and with different quality glycerol fraction, respectively.

A similar amount of
lipids was also synthesized by
Rh.
t
oruloides

but the yield of lipids per unit of glycerol
consumed was higher for

C. curvatus

2 (18.2


31 %).

The initial glycerol concentration in the medium from 10 to 100 g l
-
1

resulted in changes in the
glycerol uptake by
C. curvata

2 from 92.9 to 32.5 %, respectively. The use of a mixture of
glucose and glycerol as a carbon sour
ce indicated that glucose inhibited the glycerol uptake.
When the glucose
-
to
-
glycerol proportion was 4 : 1 (mol:mol) the glycerol uptake was 25.8 %
and when the proportion was 1 : 4 (mol:mol) the uptake increased to 78.5 %. However, the
intracellular lipid

amount and biomass growth were reduced at higher amounts of glycerol.
During the cultivation of
C. curvatus

2, the rate of glycerol uptake was lower than 0.02 g g
-
1
l
-
1

when the mixture of glucose and glycerol (3:2, mol:mol) was used and was from 0.02 to
0.09
g g
-
1
l
-
1

when glycerol was added to the medium.

The possibility to synthesize tailor
-
made lipids by yeast cultivation in the medium with
glycerol as the main carbon source will be analyzed in the future.