الفهرس 
1. IntroductionOnly 14 pages are availabe for public view
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Abstract
The present study aimed to isolate oleaginous fungi which are strong lipid
accumulators that can produce and accumulate 20% or more of their biomass as
lipid, and to study their fatty acid profiles to investigate the potentiality of these
lipids to be used as sources of valuable fatty acids which can be employed for
different applications.
Firstly, a large number of filamentous fungi and yeasts were isolated from
different soil, marine water, and food samples. Qualitative and quantitative
screening were performed to elect the organisms with the highest potential for
lipid production.
The most potent lipid producer amongst the tested isolates was identified, both
morphologically and molecularly, as the Zygomycetous fungus, Cunnighamella
echinulata AUMC 14396.
The lipid of the fungus was extracted and transesterified to produce FAMEs,
which were analyzed via GC-MS to elucidate the FA composition of the fungal
lipid. Saturated FAs dominated the FA profile with a concentration of 44.49%,
then came PUFAs (35.61%), and the lowest concentration was for MUFAs as it
was 19.91%. The medicinally important PUFA, GLA, was present in a
considerably high concentration which was 8.02% .
Optimization of culture conditions of C. echinulata AUMC 14396 for maximum
lipid production was performed. Several factors were included in the optimization
process including incubation time, inoculum concentration, carbon source,
nitrogen source, nitrogen concentration, carbon concentration, incubation
temperature, initial pH, yeast extract concentration, and salinity by addition of
different NaCl concentrations, either initially in the medium before cultivation or
at a later stage after a particular time of incubation .
The highest lipid yield was obtained at the following circumstances: incubation
time = 7 days, inoculum concentration = 5×105
spore/mL, glucose as the carbon
source at a concentration of 40 g/L, sodium nitrite (NaNO2) as the nitrogen
source at a concentration of 1 g/L, incubation temperature = 28° C, pH = 6.5,
yeast extract concentration = 7 g/L, and finally it was found best to supplement
the medium with NaCl after 72 h of incubation to yield a concentration of 1%
NaCl. The lipid yield which resulted from the cultivation of C. echinulata AUMC
14396 under these conditions was 6.7394±0.2250 g/L which is 3.3-fold the lipid
yield at the beginning of the optimization process .
The fatty acid composition of the lipid produced on the optimized medium was
obtained via GC-MS analysis, and it revealed differences from the preoptimization FA profile. Generally, PUFAs concentration was highest as
compared to the other FA groups. It increased from 35.61% before optimization
to 41.89%. The concentration of SFAs decreased by about 10%, while MUFA
concentration increased by nearly 5%. Amongst the FAs, linoleic acid had the
highest concentration (18.69%). Interestingly, the concentration of GLA
increased significantly from 8.02% to 14.82% which is a desirable increase .
A variety of industrial and agro-industrial byproducts and wastes were used as
substrates to evaluate their suitability for supporting the growth and lipid
production of C. echinulata AUMC 14396. The substrates used included
molasses, glycerol, waste cooking oil, orange peel, pasta dough waste, and olive
mill pomace, both fresh and dry .
Waste cooking oil proved to be the best substrate as the biomass and lipid
produced were 19.3413±0.9065 g/L and 10.8270±0.1842 g/L, respectively, which
were significantly high compared to any other results. Pasta dough waste came in
second place regarding biomass production as it produced 17.6843±0.4170 g/L,
but the lipid yield was much lower than that of WCO (2.6120±0.1698 g/L).
Growth on molasses resulted in the production of a biomass of 12.8383±0.1056
g/L and a lipid yield of 2.9460±0.2943 g/L which is higher than that of pasta
dough waste. The results of glycerol were close to those of molasses, although a
bit lower. Overall, all the substrates supported the growth of C. echinulata
AUMC 14396 and most supported lipid production in varying degrees .
The effects of varying the carbon sources/substrates on the fatty acid
compositions of the produced lipids were studied. The percentages of the
different fatty acids varied greatly amongst the different lipids .
In molasses, the total concentrations of SFAs and PUFAs were almost identical,
while MUFAs concentration was lower. The contents of stearic, oleic, and
linoleic acids were very similar to one another (" ~ "16%). They were followed by
GLA, the concentration of which was quite high (14.15%). This fatty acid profile
was very close to that formed on glucose .
In glycerol, SFAs had the highest concentration (45.27%), then PUFAs and
MUFAs followed (31.17% and 23.56%, respectively). Oleic acid was the one
with the highest percentage (17.08%) and GLA concentration was 9.37%.
Lignoceric acid (C24:0) was also present in a considerable amount (13.12%).
In waste cooking oil, the FA profile was very different. MUFAs had the highest
percentage (62.87%), while SFAs and PUFAs had much lower concentrations.
Oleic acid was the dominant FA with a percentage of 60.44%. However, GLA
percentage was very low (1.67%). Interestingly, the amount of the ɷ-3 FA,
docosahexaenoic acid, arose to a high level as its concentration was uniquely high
on this substrate (10.50%).
As to xylose, the percentage of SFAs was highest (40.46%). It was directly
followed by PUFAs, then MUFAs (35.02% and 24.52%, respectively). Here,
GLA recorded its highest concentration amongst all other cases, as it was
16.22% .
The effects of shifting the incubation temperature on the FA composition of C.
echinulata AUMC 14396 to a lower temperature (4°C for 30 days) were studied,
and it was found that the most significant change was the increase of the
percentage of PUFAs by about 10% to become 51.32% with GLA being the most
dominant FA as it reached 22.79% of the total fatty acids.
In conclusion, the oleaginous Zygomycetous fungus, Cunninghamella echinulata
AUMC 14396, was proven to be a good lipid producer, both on glucose and on
other low-cost substrates. It can be utilized for the production of lipids that can be
employed in various applications. By varying the substrate on which the
organism is grown and/or shifting the incubation temperature to lower degrees,
the FA profile of the lipid can be manipulated to produce FAs of desire which can
then be directed to different applications and/or industries, i.e., biodiesel
production and synthesis of medicinally important pharmaceutical and
nutraceutical products rich in PUFAs.