The isolated 23 yeast strains were precultured in inoculum medium, and then 24 h old preculture were
inoculated in 125 mL flasks containing 25 mL crude glycerol based medium and incubated for 72 h at
room temperature with shaking at 140 rpm. Among 23 isolates, four of them (BY4-523, BY4-571, JU4-
57 and BU4-598) gave high lipid yield with lipid content higher 40% when grown in crude glycerol base
medium broth. Fig. 1 shows time courses of cell growth and lipid yield of four strains. It was found that
BY4-523 accumulated highest lipid content up to 53.28% (10.28 g/L of biomass and 5.48 g/L of lipid
yield) while JU4-57 grew fastest and gave comparable high lipid content 41.50% (17.05 g/L of biomass
and 7.48 g/L of lipid yield). It should be noted that the isolated yeast strains were not inhibited by crude
glycerol. Easterling et al. [5] reported that oleaginous yeasts have the ability to grow and accumulate
lipids when grown on glycerol and have short generation times, and very minimal nutrient requirements.
It was also reported that the crude glycerol from biodiesel manufacturing contains macro elements such as
calcium, potassium, magnesium, sulfur and sodium [6]. Thus, using the crude glycerol to produce yeast
oils as biodiesel feedstock would provide an added bonus of offsetting costs of production. Yeast strains
JU4-57 and BY4-523 which gave highest lipid yield and highest lipid content, respectively, were selected
for the next study.
The isolated 23 yeast strains were precultured in inoculum medium, and then 24 h old preculture were
inoculated in 125 mL flasks containing 25 mL crude glycerol based medium and incubated for 72 h at
room temperature with shaking at 140 rpm. Among 23 isolates, four of them (BY4-523, BY4-571, JU4-
57 and BU4-598) gave high lipid yield with lipid content higher 40% when grown in crude glycerol base
medium broth. Fig. 1 shows time courses of cell growth and lipid yield of four strains. It was found that
BY4-523 accumulated highest lipid content up to 53.28% (10.28 g/L of biomass and 5.48 g/L of lipid
yield) while JU4-57 grew fastest and gave comparable high lipid content 41.50% (17.05 g/L of biomass
and 7.48 g/L of lipid yield). It should be noted that the isolated yeast strains were not inhibited by crude
glycerol. Easterling et al. [5] reported that oleaginous yeasts have the ability to grow and accumulate
lipids when grown on glycerol and have short generation times, and very minimal nutrient requirements.
It was also reported that the crude glycerol from biodiesel manufacturing contains macro elements such as
calcium, potassium, magnesium, sulfur and sodium [6]. Thus, using the crude glycerol to produce yeast
oils as biodiesel feedstock would provide an added bonus of offsetting costs of production. Yeast strains
JU4-57 and BY4-523 which gave highest lipid yield and highest lipid content, respectively, were selected
for the next study.
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