2. Materials and methods
2.1. Screening of oleaginous yeasts
The waste samples were collected from soil and waste of palm oil mill and biodiesel plant in southern
region of Thailand. 5% of samples will be enriched in 25 mL YPD medium (yeast extract 10 g/L andpeptone 10 g/L) by using 40 g/L glucose or glycerol as a carbon source at acid pH (4.0) or neutral pH
(6.0) with 0.0001% chloramphenicol. Then 0.1 mL diluted culture was isolated on YPD agar medium
using spread-plate technique for 72 h at room temperature. Total yeast strains were stained with Sudan
black B technique and observed under a phase contrast microscope on oil immersion for the presence of
blue or greyish colored fat globules within the cell [7]. The yeast strains showing fat globules within the
cell were selected for further quantitative analysis. The yeast strains were precultured in inoculum
medium, and then 24 h old preculture were inoculated in 25 mL crude glycerol based (crude glycerol 100
g/L with corresponding glycerol concentration of 40 g/L, yeast extract 10 g/L and peptone 10 g/L, pH
6.0) at the C/N molar ratio of 7.4 and incubated for 72 h at room temperature with shaking at 140 rpm.