*Non-detected
Data are expressed as the mean ± SD. The lower-case letters show the
statistical difference between cell disruption methods (P< 0.05).
According to the results of fatty acids, there were not significant
differences in the cell disruption groups compared to the control
groups. Among the total crude lipid methods, Bligh and Dyer showed
better results in terms of fatty acids. It was thought that the
temperature applied in Soxhlet damaged the lipid material. Lower fatty
acid amounts were obtained in all Soxhlet applied groups. It also
appears that Soxhlet method damaged to DHA. In the study by Guckert et
al. (1988) on lipid solvent system for the analysis of lipid classes inChlorella , Bligh and Dyer provided the most quantitative and
reproducible recovery of all Chlorella lipid classes, also,
degradation of the polyunsaturated fatty acids was observed during the
Soxhlet procedure, similar with our study. Tang et al. (2011) in their
study on supercritical CO2 and Soxhlet extraction of
lipids and enrichment of DHA from oil-rich microalgaeSchizochytrium limacinum , DHA content was obtained in these
groups as 27.5% and 15.4%, respectively. It was concluded
supercritical CO2 extraction exhibits many advantages
over the Soxhlet extraction for the DHA enrichment and purity. In our
study, cell disruption methods, particularly osmotic shock, enzyme and
HCl resulted in high yields of saturated fatty acids, monounsaturated
fatty acids and polyunsaturated fatty acids in the extracted oil. The
highest DHA was detected in the BDE group. The enzymatic hydrolysis was
shown to be an effective and nontoxic procedure for improving of
extraction efficiency of intracellular compounds (Zhang et al., 2019).
Gomes et al. (2020) reported that the microbial cell disruption using
enzymes is a promising and highly energy-efficient technology.
Furthermore, enzymatic lysis process is considered to be more
environmentally friendly (Lee et al., 2017). Taher et al. (2014) in the
study on extracting lipid with enzyme (lysozyme and cellulase) and acid
treatment from Scenedesmus sp., reported C16:0 as the major
saturated fatty acid which was 16.4 ± 0.08%, 11.9 ± 0.3% and 15.1 ±
0.2% in the enzyme lysozyme and cellulase, and acid treatments,
respectively. Total fatty acids were 84.3%, 76.9%, 79.7%, 82.2% and
79.0%, in the groups of untreated freeze-dried algae, acid treatment,
lysozyme and cellulase enzyme, respectively. Treatments decreased the
total fatty acids compared with untreated algae, especially in the acid
applied group. Yu et al. (2015) in their study investigating the effect
of autoclaving, bead-beating, microwaving, sonication, acid (HCl)
digestion, and Soxhlet extraction to lipid extraction fromChlorella sorokiniana , declared that in Soxhlet method saturated
fatty acids 16:0 and 18:0 were affected, and lower results were obtained
compared with other methods. In autoclaving and microwaving methods,
16:1, 18:0, 18:2 and 18:3 were not obtained when these fatty acids were
relatively high in HCl digestion, especially for 18:2 with 28.9 ± 1.4%.
In our study, most of fatty acids were obtained with HCl digestion.
Although HCl that was reported to cause harm in the literature, did not
cause any loss in fatty acids in our study. But Taher et al. (2014)
reported that using acids requires special materials of construction,
which is not economic for large-scale applications. Safety issues, and
wastewater treatment are also essential for strong acid treatment (Lee
et al., 2017) and it is thought that the method will not be safe in
applications such as feed, food and cosmetics. In our study, effective
results were obtained in terms of fatty acids in the OS and UH groups
with the BD method. In the study by Prabakaran and Ravindran (2011) on
cell disruption methods (autoclaving, bead beating, microwave,
sonication, 10% NaCl solution) for lipid extraction fromChlorella sp., Nostoc sp. and Tolypothrix sp.
sonication was found as the most effective method. Osmotic shock has
advantages such as; lower energy consumption, easier scale-up, faster
extraction- suitable for all cell types, however it has disadvantages
like generation of waste salt water, salt’s high cost (Lee et al., 2017)
time consuming. Sonication also has disadvantages such as damaging
chemical structure of molecules (Byreddy et al., 2015).
In the present study, palmitic acid and DHA constitute most of the total
fatty acids. It is an expected result that palmitic is high in aquatic
plants, and the high amount of DHA, as a valuable fatty acid in terms of
human health, is an important criterion. High DHA adds value to our
product. It is thought that the evaluation of this algae for use in
areas such as food and feed will make an important contribution. Ju et
al. (2020) in their study the resulting microalgal lipids are mainly
docosahexaenoic acid (DHA) and palmitic acid, also they reported
palmitic acid is a saturated fatty acid (SFA) that is used as an
emollient and diluent in the cosmetics industry. Fedorova-Dahms et al.
(2011) reported that Schizochytrium sp. oil contains 40-45% DHA
and up to 10% EPA. Leaño et al. (2003) found the amount of lipid in the
range of 13.0-39.1%, in their studies of growth and fatty acid
production of Schizochytrium sp. at different salinity and
temperatures. In the study by Li et al. (2009) on was usedSchizochytrium as supplements in Ictalurus punctatus feed,
the highest PUFA in dry algae was determined as DHA with 31.39% and
Ʃn-3 PUFA was 37.08%. It was concluded that addition of 2% dried algae
in the diet markedly improves the levels of 22:6 n-3 and Ʃn-3 LC-PUFAs
in the edible tissue of fish. DHA and palmitic acid were high in %
total fatty acids similar with our study. In our study; ƩSFA, ƩMUFA and
ƩPUFA were obtained in the range of 67.08-85.82%, 7.38-10.53%, and
4.91-20.87%, respectively. In the study of Byreddy et al. (2015)
saturated, monounsaturated and polyunsaturated fatty acids were obtained
in the range of 49%-57%, 31%-35% and 2%-18%, respectively forSchizochytrium sp.. ƩPUFA obtained in our study higher than that
reported by Byreddy et al. (2015). n-3 FAs have beneficial effects
against chronic metabolic diseases, such as obesity, diabetes, and
cardiovascular diseases, different cancers, asthma, inflammatory bowel
disease, rheumatoid arthritis, psoriasis and osteoporosis (Prato et al.,
2019). Because of their health benefits of long-chain n-3
polyunsaturated fatty acids, especially DHA, consumer preference
increased for the products fortified with these desirable nutrients (Liu
et al., 2020). n-3, n-6 and n-3/n-6, DHA/EPA, PUFA/SFA, unsaturated
(UNS)/SFA ratios are widely used to evaluate the nutritional value of
lipid (Prato et al., 2019). In our present study Ʃn-3 and Ʃn-6 were
detected between 4.58 ± 2.44-19.53 ± 0.09% and 0.33 ± 0.07-1.79 ±
0.00%, respectively. n-6/n-3 ratio was detected in the range of 0.06 ±
0.00-0.09 ± 0.09. Gonçalves et al. (2021) reported that n-6/n-3 ratio
below 4.0 in a diet indicates desirable quantities for human health. In
our study, this ratio was below the limits that Gonçalves et al. (2021)
reported, in our study. Increasing consumption of fish and fish products
rich in n-3 PUFA (polyunsaturated fatty acids), which is important for
human health, and poor in n-6 PUFA, should be encouraged (Metin et al.,
2021). PUFA/SFA ratio was obtained between 0.06 ± 0.03-0.31 ± 0.00
values. Due to the high content of palmitic acid, this ratio was
obtained at low levels. However, the values were close to the minimum
limit value of 0.45 specified by Gonçalves et al. (2021) and Liu et al.
(2020) except for the SC group.
As a result; as Zhang et al. (2019) reported; compared with conventional
methods, the use of emerging techniques allowed the recovery
bio-molecules avoiding toxic solvent, high temperature and treatment
time.