After production of yeast lipid from industrial wastes, the yeast
lipid was converted into biodiesel by the transesterification process.
The transesterification of yeast lipid was performed according
to the three procedures as shown in Fig. 1. In Procedure I, the lipid
was extracted from yeast cells prior to transesterification. The effect
of molar ratio of methanol to oil was investigated by varying
the ratio at 20:1, 42:1, 84:1 and 125:1 (Fig. 4). The compositions
of the yeast lipid at the initial time were triglyceride (TG) 48.3%,
diglyceride (DG) 7.8%, monoglyceride (MG) 25.7% and free fatty
acid (FFA) 18.2%. Normally an alkali catalyst is used in the transesterification
reaction of plant oil, but in case of yeast lipid that contains
high amount of free fatty acids the alkali would react with
these free fatty acids and produced a soap instead of the methyl esters.
Therefore, this yeast lipid was transesterified by using acid as
the catalyst. The sulfuric acid was added at a concentration of
0.4 M. At a low methanol molar ratio of 20:1 (Fig. 4a), no significant
amount of fatty acid methyl ester (FAME) was produced.
The MG decreased rapidly coupled with a rapid increase of FFA
during the first 30 min of the reaction and gradually increased until
3 h. An increase of the methanol molar ratio up to 42:1 (Fig. 4b) resulted
in an increase of FAME up to 15% but it took a very long
reaction time of 24 h. A further increase of the methanol molar ratio
up to 84:1 (Fig. 4c) did increase the production of FAME up to
72% within 3 h of the reaction time coupled with a rapid decrease
of the TG to almost zero.
After production of yeast lipid from industrial wastes, the yeast
lipid was converted into biodiesel by the transesterification process.
The transesterification of yeast lipid was performed according
to the three procedures as shown in Fig. 1. In Procedure I, the lipid
was extracted from yeast cells prior to transesterification. The effect
of molar ratio of methanol to oil was investigated by varying
the ratio at 20:1, 42:1, 84:1 and 125:1 (Fig. 4). The compositions
of the yeast lipid at the initial time were triglyceride (TG) 48.3%,
diglyceride (DG) 7.8%, monoglyceride (MG) 25.7% and free fatty
acid (FFA) 18.2%. Normally an alkali catalyst is used in the transesterification
reaction of plant oil, but in case of yeast lipid that contains
high amount of free fatty acids the alkali would react with
these free fatty acids and produced a soap instead of the methyl esters.
Therefore, this yeast lipid was transesterified by using acid as
the catalyst. The sulfuric acid was added at a concentration of
0.4 M. At a low methanol molar ratio of 20:1 (Fig. 4a), no significant
amount of fatty acid methyl ester (FAME) was produced.
The MG decreased rapidly coupled with a rapid increase of FFA
during the first 30 min of the reaction and gradually increased until
3 h. An increase of the methanol molar ratio up to 42:1 (Fig. 4b) resulted
in an increase of FAME up to 15% but it took a very long
reaction time of 24 h. A further increase of the methanol molar ratio
up to 84:1 (Fig. 4c) did increase the production of FAME up to
72% within 3 h of the reaction time coupled with a rapid decrease
of the TG to almost zero.
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