The results in Fig. 3a confirmed that among the wastes tested
the crude glycerol, especially at 4% glycerol concentration
(Fig. 3a: E), was the most suitable source for lipid production by
Y. lipolytica TISTR 5151 followed by palm oil mill effluent without
dilution (Fig. 3a: A). The results also showed that crude glycerol
could be used as a good co-substrate to palm oil mill effluent
(Fig. 3a: D) to increase the lipid production. Although the use of
serum latex alone (Fig. 3a: G) gave very low amount of lipid, the
use of 3-fold diluted serum latex added with either crude glycerol
(Fig. 3a: J) or molasses (Fig. 3a: M) significantly increased the lipid
production. The lipids produced from single and some combined
industrial wastes shown in Fig. 3a were further analyzed for their
fatty acid compositions (Table 3). Among the single industrial
wastes tested, crude glycerol gave the highest content of oleic acid
(41.1%) followed by palm oil mill effluent (39.3%) and serum
(32.2%). Moreover, when crude glycerol was used as a co-substrate
with palm oil mill effluent (D: POME + CG4%) and serum latex (J:
Serum1/3 + CG4%) the content of oleic acid increased from 39.3
to 43.6% and from 32.2 to 49.1%, respectively. It should be noted
that the use of glycerol also increased both the ratio of C18 to
C16 and the ratio of unsaturated fatty acids (USFA) to saturated
fatty acids (SFA). The similar result was also observed when molasses
was added into the 3-fold diluted serum latex (M: Serum1/
3 + Molasses4%). This implied that the use of glycerol and a high
C/N ratio positively affected the elongation and desaturation process
of fatty acid biosynthesis of Y. lipolytica TISTR 5151. The longer-
chain and higher content of unsaturated fatty acids would
provide excellent fuel properties at low temperatures, which is
an advantage for operations in winter.