Solid byproducts of Aurantiochytrium sp. oil made into the biodiesel
Shu-Yao Tsai．Hsiang-Yu Lin．Guan-Yi Lu．Chun-Ping Lin*
Abstract Microalgae have rich oil production under full photosynthesis, which reaches over 50 mass%. In addition,
microalgae oil contains the prolific cis-4,7,10,13,16,19-docosahexaenoic acid (DHA) that is usually refined for making
health food or food additives. This study investigated Aurantiochytrium sp., which is a kind of microalgae, the oil of
which is also refined for use in health food or food additives. The solid byproducts of Aurantiochytrium sp. oil are more
than 20 mass%, discarded as rubbish. Fortunately, the solid byproducts have been found to contain a large amount of
palmitic acid that exceeds more than 67 mass%, but it is difficult to transesterify from the solid byproducts of
Aurantiochytrium sp. oil, such as the waste cooking oil or waste engine oil, which contain many impurities. Thus, the
impurities, the free fatty acids, and the microalgae cell wall of solid byproducts interfere with transesterification.
Sequences of saponification, reduction reaction, and acid-catalyzed reactions were conducted for the full process of
transesterification in this study. Gas chromatography (GC) analysis, differential scanning calorimetry (DSC) thermal
analysis, and Fourier transform infrared spectroscopy (FTIR) repeatedly corroborated the results of the transesterification,
which proved that the solid byproducts of Aurantiochytrium sp. oil form a high yield and high quality biodiesel. Overall,
we have successfully obtained more than 92 mass% transesterification rate from the solid byproducts of
Aurantiochytrium sp. oil. The solid byproducts are waste turned into gold.
Keywords: Microalgae oil．cis-4,7,10,13,16,19-Docosahexaenoic acid (DHA)．Aurantiochytrium sp．Palmitic acid．
Biodiesel
S.-Y. Tsai．G.-Y. Lu
Department of Health and Nutrition Biotechnology, Asia University, 500, Lioufeng Rd., Wufeng, Taichung, Taiwan
41354, ROC
H.-Y. Lin
Department of Neonatology, Children’s Hospital, China Medical University Hospital, China Medical University, 2, Yude
Rd., Taichung 40447, Taiwan, ROC
C.-P. Lin ( )
Department of Health and Nutrition Biotechnology, Asia University, 500, Lioufeng Rd., Wufeng, Taichung 41354,
Taiwan, ROC & Department of Medical Research, China Medical University Hospital, China Medical University, 91,
Hsueh-Shih Rd., Taichung 40402, Taiwan, ROC
e-mail: cp.lin@asia.edu.tw; chunping927@gmail.com
1
Introduction
Microalgae have rich oil under full photosynthesis, which reaches over 50 mass%. In addition, the
microalgae oil contains the prolific cis-4,7,10,13,16,19- docosahexaenoic acid (DHA) (C22H32O2)
that is usually refined for making into health food or food additives. In fact, dietary DHA may reduce
the risk of heart disease by reducing the level of blood triglycerides in humans. Below-normal levels
of DHA have been associated with Alzheimer's disease. A low level of DHA is also seen in patients
with retinitis pigmentosa [1–3].
This study focused on Aurantiochytrium sp., which is a kind of microalgae, the oil of which is
also refined for DHA for making into health food or food additives. Specifically, the DHA
manufactured using microalgae can be supplied to vegetarians. More than 20 mass% of the solid
byproducts of Aurantiochytrium sp. oil are discarded as rubbish under current operating procedures
in food factories. Fortunately, the solid byproducts include rich palmitic acid that exceeds upper of
67 %. There are two critical points about good biodiesel from a green energy plant. First, it neither
crowds out food farming nor occupies arable land. Secondly, the biodiesel could be done in
large-scale production from a green energy plant. This study is in line with the specifications.
It is difficult to transesterify from the solid byproducts of Aurantiochytrium sp. oil, because waste
cooking oil or waste engine oil, for example, contains many impurities [4–7]. The impurities, the free
fatty acids, and the microalgae cell wall of solid byproducts interfere with transesterification.
Therefore, we conducted the full process of transesterification by sequences of saponification,
reduction reaction, and acid-catalyzed reactions. We also focused on biomass oil, which could
become high quality environmentally friendly diesel, including a suitable transesterification process
for biodiesel and the highest yield of biodiesel from the solid byproducts of Aurantiochytrium sp. oil
[8].
We used differential scanning calorimetry (DSC) to determine the melting temperature, the
crystallization temperature, and the enthalpy of endothermic and exothermic of the crude, the solid
byproducts, and the refined liquid oil of Aurantiochytrium sp. oil [9–21]. In addition, gas
chromatography (GC) was applied to analyze the fatty acid profile and the results of
transesterification of Aurantiochytrium sp. oil [22, 23]. Fourier transform infrared spectroscopy
(FTIR) was also used in the results of transesterification for identifying the characteristic functional
groups [24]. Therefore, developing high quality environmentally friendly diesel from the solid
byproducts of Aurantiochytrium sp. oil in this study is an important project.
Overall, we needed to overcome the difficulties of transesterification to obtain a high
transesterification rate from the solid byproducts of Aurantiochytrium sp. oil. Thus, this study is a
complete, forward-looking and innovative research project in green energy. From such a perspective,
this project addresses the problem of making full use of marine resources and turning waste into
gold.
Materials and methods
Samples
Aurantiochytrium sp. oil, which was supplied directly from VEDAN Enterprise Corp. in Taiwan, was
stored frozen at –20 °C. The manufacturing and refining process flow diagram of the
Aurantiochytrium sp. oil is in Fig. 1, and the original fatty acid profile of Aurantiochytrium sp. oil
provided by VEDAN Enterprise Corp. is given in Table 1.
Refined solid byproducts of Aurantiochytrium sp. oil
We first prepared to refine the solid byproducts of Aurantiochytrium sp. oil, which could not directly
be transesterified into biodiesel by general transesterification. The solid byproduct was heated above
60 °C for melting, and then sifted by 20 mesh cloth for preliminary refining. Important composition
and experimental data of the preliminary refined solid byproducts was also estimated; the fat content
2
was 56.5 ± 2.7 mass%, the moisture was 0.4 mass%, and the acid value was 1.7 mg KOH g–1,
individually. The goal was a fixed fatty acid composition, which was saponified with sodium
hydroxide under ca. 90 °C for two hours, and then the impurities, the free fatty acids, and the
microalgae cell were removed to form the microalgal oil soap. The microalgal oil soap then
underwent further transesterification.
Transesterification
The solid byproducts of Aurantiochytrium sp. oil contained more than 56 mass% of fatty acid.
Relatively, the impurities of solid byproducts were also beyond more than 40 mass%, which would
interfere with transesterification. It is very important to overcome the obstruction of impurities for
conducting transesterification of the solid byproducts [5–8]. Therefore, the sequences of
saponification, reduction reaction, and acid-catalyzed reactions were conducted for the full process
of transesterification. From the above-mentioned via saponification, which excluded the impurities,
the free fatty acids, and the microalgae cell, we could obtain high purity fatty acid for the next step of
the reduction reaction by mixed sulfuric acid (2NaOH + H2SO4→Na2SO4 + 2H2O). The reduction
reaction was mixed with sulfuric acid to form the fatty acids under 85–90 °C for two hours. Finally,
the acid-catalyzed reactions were mixed with dil. sulfuric acid (< 0.02 mass% ratio of fatty acid) and
methanol (fatty acids: methanol = 1:5 weight ratio) under reflux for overnight.
Gas chromatography (GC) analysis
Fatty acid methyl esters (FAMEs) were analyzed by gas chromatograph (Agilent 6890N) equipped
with a flame ionization detector (GC-FID) and a Restek Rt-2340 NB Cap. column (105 m × 0.25 mm
× 0.20 µm). The oven temperature was initially set at 170 °C, and then programmed to 250 °C using
helium as the carrier gas at a flow rate of 1.1 mL min–1 and held for 30 min. The injector and detector
temperatures were 250 °C. The split ratio was 1:80. Fatty acids were identified by comparing the
retention time of FAME peaks with Supelco 37 FAME mixture standards (Sigma). Results were
expressed as relative percentage of each fatty acid calculated by internal normalization of the
chromatographic peak area [22, 23]. The fatty acid profile of solid byproducts of Aurantiochytrium
sp. oil and fatty acid methyl esters composition of microalgae biodiesel by GC analysis are listed in
Tables 2 and 3, respectively.
Differential scanning calorimetry (DSC) tests
Temperature–programmed screening experiments were performed with DSC (TA Q20). DSC
analysis on samples sealed in 20 μL hermetic aluminum pans; the test cell was sealed manually by a
special tool equipped with TA’s DSC. In all studies with DSC, nitrogen was the carrier gas with a
flow rate of 50 mL min–1 [18–20]. ASTM E698 was used to obtain thermal curves for analyzing the
parameters. About 1.7 to 2.0 mg of the sample was used for acquiring the experimental data.
Non-isothermal tests of the scanning rate selected for the programmed temperature ramp were 2, 4, 6,
and 8 °C min–1 for the range of temperature rise chosen from 30–65 °C and then cooled to –30 °C for
each endothermic and exothermic reaction experiment, and from 30–300 °C for each thermal
stability and phase behavior experiment, respectively.
Infrared spectroscopy analysis
The fatty acids of Aurantiochytrium sp. oil’s solid byproducts and the fatty acid methyl esters of
microalgae biodiesel were deposited dropwise onto a KBr disc from a concentrated dichloromethane
solution, respectively [24]. Evaporation of the solvent resulted in a uniform film. Infrared spectra
were acquired using a Bruker Alpha FTIR spectrometer. Spectra were collected in the transmission
mode with an unpolarized light beam, at a resolution of 4 cm–1 with six scans, and a spectral range of
4000–400 cm–1. Background spectra of the clean KBr disc were collected at the same temperatures
and subtracted from the sample spectra.
3
Results and discussion
The results of transesterification
The study was via GC to obtain the profile of fatty acids and fatty acid methyl esters of the solid
byproducts of Aurantiochytrium sp. Fatty acid carbon chain length for the possibility of becoming
biodiesel is an important crucial factor. Generally, the C12–C22 of the fatty acids is most suitable as
biodiesel. It is an important quality indicator of biodiesel; the greater proportion of fat and the highly
transesterified rate are as the bio-oil into biodiesel. The fatty acid and FAME content (mass %) was
calculated using the following equation [22, 23]:
c
(  E ) Emh
C V
 mh mh  100
Emh
M
where ΣE is the total peak area of methyl esters from C14–C24:1, Emh is the peak area representing
methyl heptadecanoate, Cmh is the concentration of methyl heptadecanoate solution used (mg mL–1),
Vmh is the volume of the methyl heptadecanoate solution used (mL), and M is the sample mass (mg).
Table 2 shows the fatty acid profile of solid byproducts from GC analysis, which verified the
fatty acid composition of the solid byproducts again. Comparing Tables 1 and 2 and Fig. 2, we
confirmed the amount of palmitic acid and DHA was more than 75 mass% of total fatty acids. In
addition, from Table 2, the C14–C18 of the fatty acids were more than 79 mass% of the total fatty
acid profile. For the free fatty acids and the microalgae cell wall, many impurities were removed by
saponification and reduction reaction. There are advantages in the subsequent transesterification of
solid byproducts.
Table 3 and Fig. 3 show the high ratio of transesterification exceeded 92 mass% and the amount
of C14–C18 was also more than 89 mass% by acid-catalyzed reactions in this study. From the
sequences of saponification, reduction reaction, and acid-catalyzed reactions which were conducted
for the full process of transesterification, which excluded the impurities, the free fatty acids, and the
microalgae cell wall, we successfully obtained a high ratio method of transesterification for the solid
byproducts of Aurantiochytrium sp. oil.
DSC analysis
The phase behavior of Aurantiochytrium sp. oil has been characterized by DSC in terms of the
temperature and the enthalpy of the phase transition. From Figs. 4–6, the DSC curves clearly show
that the crude oil, the refined liquid oil, and the solid byproducts, in the liquid and solid state undergo
distinct phase transitions, respectively, which can be associated with the refining method and
separate control technology. Three conditions of the onset temperature, the peak maximum
temperature, and the endothermic and exothermic reaction of enthalpy associated with the DSC
transition, were found for the thermal characteristics of the crude oil, refined liquid oil, and solid
byproducts. In fact, the DSC peak maximum temperature and enthalpy measured for the crude oil,
the refined liquid oil, and the solid byproducts very clearly discriminate the differences. The detailed
results of DSC analysis are listed in Table 4.
Figure 4 shows that the DSC curve programmed temperature ramp was 2, 4, 6, and 8 °C min–1
for the range of temperature rise chosen from 30–65 °C and then cooled to –30 °C for each crude oil
experiment. For the unrefined crude oil, though there was a deviation from the baseline, we can see
at 30–65 °C an obvious endothermic peak as that of unrefined crude oil, but 65 °C cooled to –30 °C
has two exothermic peaks for exhibiting a significant crystallization reaction. Moreover, Figs. 5 and
6 indicate a trace of DHA and saturated fatty acids of different content, which influenced the thermal
characteristics of Aurantiochytrium sp. oil by DSC tests. In comparisons of Figs. 4–6, Fig 4 of DSC
curves was almost a hybrid of Figs. 5 and 6.
Figures 7 and 8 show DSC non-isothermal tests of the scanning rate selected for the programmed
temperature ramp were 2, 4, 6, and 8 °C min–1 for the range of temperature rise chosen from 30–300
°C for each and phase behavior experiment, respectively. From Fig. 7, a peak maximum temperature
4
of ca. 62 °C was previously reported (Fig. 6) for the phase transition of solid byproducts of
Aurantiochytrium sp. oil. The main phase transition temperatures are phase behavior by heat, which
could prove the main component of palmitic acid in the solid byproducts of Aurantiochytrium sp. oil
again. Figure 8 shows the biodiesel of solid byproducts compared to the full DSC curves of solid
byproducts (Fig. 7). The biodiesel of solid byproducts (which are heated beyond more than the peak
maximum temperature 170 °C that will be converted into gases) is liquid at room temperature. The
main transition peak is a factor of biodiesel of solid byproducts of Aurantiochytrium sp. oil. The
detailed results of DSC tests of the solid byproducts and biodiesel of solid byproducts of
Aurantiochytrium sp. oil at various with scanning rates of 2, 4, 6, and 8 °C min–1 for performing the
range of temperature from 30–300 °C are listed in Table 5.
Infrared spectroscopy
From Fig. 9, we observed the hydroxyl (–OH) groups of long carbon chain of carboxylic acid; the
stretching-vibration absorption peak wavenumbers were 3600–3300 cm–1 and 2800–2600 cm–1, the
stretching-vibration absorption peak wavenumbers were 930 cm–1 and 750 cm–1, which the
characteristic functional group of fatty acids clearly exhibited in the IR spectrum. In addition, for the
carbonyl group (–C=O) of carboxylic acids, the stretching-vibration absorption peak wavenumber
was 1760 cm–1, the C–O stretching-vibration absorption peak wavenumber was 1320–1210 cm–1, and
C–O–H bending-vibration absorption peak wavenumber was 1440–1395 cm–1, respectively, which
are also clearly shown in the spectrogram.
Comparisons of Figs. 9 and 10 indicate that the hydroxyl (–OH) groups in fatty acids could
generate methyl groups (–O–CH3) through methyl transesterification. Figure 10 shows the hydroxyl
group in fatty acid was gradually transesterified, the stretching-vibration absorption peaks
(3600–3300 cm–1 and 2800–2600 cm–1) gradually disappeared, along with the hydroxyl (–O–H)
stretching-vibration absorption peak wavenumbers 930 cm–1and 750 cm–1, and the C–O–H
bending-vibration absorption peak wavenumbers 1440–1395 cm–1 gradually disappeared too.
The above transesterified results of fatty acid via GC analysis, DSC tests, and FTIR spectrogram
repeatedly corroborated the accuracy of the transesterification, proving that the solid byproducts of
Aurantiochytrium sp. oil form biodiesel. Therefore, we overcame the difficulties of
transesterification to obtain a highly transesterified rate from the solid byproducts of
Aurantiochytrium sp. oil.
Conclusion
Overall, we have obtained a more than 92 % transesterified rate from the solid byproducts of
Aurantiochytrium sp. oil. Sequences of saponification, reduction reaction, and acid-catalyzed
reactions were conducted for the full process of transesterification, which excluded the impurities,
and successfully obtained a high ratio of transesterification for the solid byproducts. Moreover, GC
analysis, DSC thermal analysis, and FTIR spectrum repeatedly corroborated the results of the
transesterification, which proved that the solid byproducts of Aurantiochytrium sp. oil form a high
yield and high quality biodiesel.
This study is a complete, forward-looking and innovative research project in green energy. From
this perspective, the project addresses the problem of making full use of marine resources and
turning waste into gold. In the future, we will enhance the transesterification technology for the solid
byproducts of Aurantiochytrium sp. oil to find improved energy efficiency and a less polluting
method in the mass production of green energy. The energy crisis problem is not just a country's
problem, but also one that has to be faced around the world.
5
Acknowledgments
The authors are indebted to the donors of National Science Council (NSC), Taiwan, R.O.C. under the
contract No.: NSC 102-2221-E-468-001-MY2 for financial support. In addition, we are grateful to
VEDAN Enterprise Corp. in Taiwan for providing the microalgae oil.
6
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8
Table captions
Table 1 Aurantiochytrium sp. oil major fatty acid profile.
Table 2 GC analysis results of the fatty acid profile of solid byproducts.
Table 3 GC analysis results of fatty acid methyl ester composition of microalgae biodiesel.
Table 4 Results of DSC tests of the crude oil, refined liquid oil, and solid byproducts with
scanning rate 2, 4, 6, and 8 °C min–1 of the range of temperature rise chosen from 30–65 °C and then
cooling to –30 °C.
Table 5 Results of DSC tests of the solid byproducts and biodiesel with scanning rate 2, 4, 6,
and 8 °C min–1 of the range of temperature rise chosen from 30–300 °C.
9
Table 1
Aurantiochytrium sp. oil major fatty acid profile.
Sample
DHA/mass%
Palmitic acid/mass% Total fatty acid/mass%
Crude oil
35.9
39.1
90.8
Refined liquid oil
38.4
34.2
88.4
Solid byproduct
11.7
67.9
91.5
18
Table 2
GC analysis results of the fatty acid profile of solid byproducts.
Fatty acid
Myristic acid
Pentadecanoic acid
Palmitic acid
Palmitoleic acid
Heptadecanoic acid
Stearic acid
Oleic acid
Linoleic acid
Erucic acid
Docosadienoic acid
Lignoceric acid
Neryonic acid
cis-4,7,10,13,16,19-Docosahexaenoic acid
Total saturation
Form
C14:0
C15:0
C16:0
C16:1
C17:0
C18:0
C18:1n9c
C18:2n6c
C22:1n9
C22:2
C24:0
C24:1
C22:6n3
mass%
4.94
2.11
67.26
0.48
0.88
1.97
1.85
0.19
0.45
0.25
0.45
2.84
16.33
77.64
22.36
Total unsaturation
18
Table 3
GC analysis results of fatty acid methyl ester composition of microalgae biodiesel.
Fatty acid methyl ester
Myristic acid methyl ester
Pentadecanoic acid methyl ester
Palmitic acid methyl ester
Palmitoleic acid methyl ester
Heptadecanoic acid methyl ester
Stearic acid methyl ester
Oleic acid methyl ester
Oleic acid methyl ester
Lignoceric acid methyl ester
cis-4,7,10,13,16,19-Docosahexaenoic acid methyl ester
Total esters
18
Form
mass%
C14:0
C15:0
C16:0
C16:1
C17:0
C18:0
C18:1n9c
C18:2n6c
C24:0
C22:6n3
6.06
2.61
78.43
0.20
0.89
1.54
0.08
0.03
0.06
3.26
93.16
Table 4
Results of DSC tests of the crude oil, refined liquid oil, and solid byproducts with scanning rate 2, 4, 6, and 8 °C min–1 of the range of
temperature rise chosen from 30–65 °C and then cooling to –30 °C.
Sample
Crude
oil
Refined
Liquid oil
Solid
byproduct
Massa Conditionb
1.9
1.9
1.9
1.9
2.0
1.8
1.8
1.8
1.8
1.8
2.0
2.0
2
4
6
8
2
4
6
8
2
4
6
8
EndoToc
EndoTpd
EndoΔHe
1ExoTof
1ExoTpg
1ExoΔHh
2ExoToi
2ExoTpj
2ExoΔHk
39.6
39.9
39.8
40.3
N/A
N/A
N/A
N/A
56.0
56.4
59.0
59.0
48.4
47.5
47.3
45.9
N/A
N/A
N/A
N/A
59.7
59.9
61.1
61.2
14.7
14.6
15.1
11.0
N/A
N/A
N/A
N/A
137.1
115.7
125.2
128.6
23.5
21.0
22.2
21.1
3.4
3.1
3.1
2.9
38.2
37.7
37.3
37.2
19.2
15.8
17.5
12.9
-4.6
-3.0
-2.9
-3.1
36.9
36.6
36.0
36.1
-10.4
-8.3
-11.1
-7.8
-45.9
-47.4
-48.6
-43.5
-120.2
-106.9
-110.5
-99.5
3.1
-0.2
-0.9
2.3
N/A
N/A
N/A
N/A
7.3
7.2
7.2
1.6
2.1
-1.9
-3.5
-4.9
N/A
N/A
N/A
N/A
4.5
4.2
-1.4
-1.9
-43.9
-40.7
-42.3
-37.7
N/A
N/A
N/A
N/A
-9.7
-9.9
-10.6
-9.5
Mass: sample mass (mg). bHeating condition: non-isothermal DSC test (°C min–1). cOnset temperature of endothermic reaction (°C). dPeak temperatureof endothermic reaction (°C).
Enthalpy of endothermic reaction (kJ kg–1). fOnset temperature of first peak of exothermic reaction (°C). gPeak temperature of first peak of exothermic reaction (°C). hEnthalpy of first
peak of exothermic reaction (kJ kg–1). iOnset temperature of second peak of exothermic reaction (°C). jPeak temperature of second peak of exothermic reaction (°C). k Enthalpy of
second peak of exothermic reaction (kJ kg–1).
a
e
Remarks: Standard deviation: temperature accuracy: +/- 0.1; temperature precision: +/- 0.05
calorimetric reproducibility: +/- 1 mass%; sensitivity: 1.0 uW.
20
Table 5
Results of DSC tests of the solid byproducts and biodiesel with scanning rate 2, 4, 6, and 8 °C
min–1 of the range of temperature rise chosen from 30–300 °C.
Sample
Solid
byproduct
Biodiesel
Massa
Conditionb
EndoToc
EndoTpd
EndoΔHe
1.9
2.0
2.0
1.7
2.0
1.8
1.8
1.8
2
4
6
8
2
4
6
8
58.2
60.3
57.1
62.3
170.0
114.0
179.2
165.5
62.4
62.0
62.8
63.9
177.0
183.8
189.6
195.0
151.0
151.2
103.4
159.1
44.4
114.0
68.0
127.3
Mass: sample mass (mg). bHeating condition: non-isothermal DSC test (°C min–1). cOnset temperature of endothermic
reaction (°C). dPeak temperature of endothermic reaction (°C). eEnthalpy of endothermic reaction (kJ kg–1).
a
Remarks: Standard deviation: temperature accuracy: +/- 0.1; temperature precision: +/- 0.05
calorimetric reproducibility: +/- 1 mass%; sensitivity: 1.0 uW.
20
Figure captions
Fig. 1. The manufacturing and refining Aurantiochytrium sp. oil process flow diagram.
Fig. 2. Results of the fatty acid profile of solid byproducts by GC analysis.
Fig. 3. Results of the fatty acid methyl ester composition of solid byproducts by GC analysis.
Fig. 4. DSC thermal curves of heat flow versus temperature for the crude oil with scanning rate 2,
4, 6, and 8 °C min–1 of the range of temperature rise chosen from 30–65 °C and then cooling to –30
°C.
Fig. 5. DSC thermal curves of heat flow versus temperature for the refined liquid oil with
scanning rate 2, 4, 6, and 8 °C min–1 of the range of temperature rise chosen from 30–65 °C
and then cooling to –30 °C.
Fig. 6. DSC thermal curves of heat flow versus temperature for the solid byproducts with
scanning rate 2, 4, 6, and 8 °C min–1 of the range of temperature rise chosen from 30–65 °C
and then cooling to –30 °C.
Fig. 7. DSC thermal curves of heat flow versus temperature for the solid byproducts at various
scanning rate 2, 4, 6, and 8 °C min–1 of the range of from 30–300 °C.
Fig. 8. DSC thermal curves of heat flow versus temperature for the microalgae biodiesel at various
scanning rate 2, 4, 6, and 8 °C min–1 of the range of temperature from 30–300 °C.
Fig. 9. FTIR spectrogram of microalgae oil’s solid byproducts.
Fig. 10. FTIR spectrogram of the biodiesel of microalgae oil’s solid byproducts.
21
Fig. 1.
The manufacturing and refining Aurantiochytrium sp. oil process flow diagram.
Fig. 2.
Results of the fatty acid profile of solid byproducts by GC analysis.
Fig. 3.
Results of the fatty acid methyl ester composition of solid byproducts by GC analysis.
22
Fig. 4. DSC thermal curves of heat flow versus temperature for the crude oil with scanning rate 2,
4, 6, and 8 °C min–1 of the range of temperature rise chosen from 30–65 °C and then cooling to –30
°C.
Fig. 5. DSC thermal curves of heat flow versus temperature for the refined liquid oil with
scanning rate 2, 4, 6, and 8 °C min–1 of the range of temperature rise chosen from 30–65 °C
and then cooling to –30 °C.
23
Fig. 6. DSC thermal curves of heat flow versus temperature for the solid byproducts with
scanning rate 2, 4, 6, and 8 °C min–1 of the range of temperature rise chosen from 30–65 °C
and then cooling to –30 °C.
Fig. 7. DSC thermal curves of heat flow versus temperature for the solid byproducts at various
scanning rate 2, 4, 6, and 8 °C min–1 of the range of from 30–300 °C.
24
Fig. 8. DSC thermal curves of heat flow versus temperature for the microalgae biodiesel at various
scanning rate 2, 4, 6, and 8 °C min–1 of the range of temperature from 30–300 °C.
Fig. 9.
FTIR spectrogram of microalgae oil’s solid byproducts.
25
Fig. 10.
FTIR spectrogram of the biodiesel of microalgae oil’s solid byproducts.
26