Abstract

Microbial lipid was produced by the soil isolated oleaginous yeast Torulaspora maleeae Y30 using glucose in flask-batch fermentation. At low concentration of nitrogen, maximum lipid production rate was observed; while high nitrogen concentration (0.4 g/l) resulted in high volumetric cell mass production rate (0.960 g/l d) and specific growth rate (0.266 d^-1). The isolated yeast T. maleeae Y30 had maximum values of 0.382 g/l d, 0.507 g lipid/g cells, 3.06 g/l and 0.105 g/L d for volumetric lipid production rate, specific yield of lipid, lipid concentration and specific rate of lipid production, respectively when culture was performed in nitrogen-limiting medium supplemented with 90 g/l glucose and 0.2 g/l (NH₄)₂SO₄. The Monod’s constant (K_S, g/l) and µ_max (1/d) of 24.52 and 0.156, were obtained, respectively. The three major constituent fatty acids of the isolated yeast T. maleeae Y30 were palmitic acid, stearic acid and oleic acid that are comparable to vegetable oils, suggesting that, microbial lipid from these yeast can be used as potential feedstock for biodiesel production.

Key words: Microbial lipid, oleaginous yeast, Torulaspora maleeae Y30, biodiesel.

Abbreviation

K_s, Monod’s constant; P, lipid concentration (g/l); Q_P, volumetric lipid production rate (g/Ld); Q_S, volumetric substrate consumption rate (g substrate/L d); Q_X, volumetric cell mass production rate (g cells/L d); q_p, specific rate of lipid production (g lipid /g cells d); q_s, specific rate of substrate consumption (g substrate/g cells d); S, substrate concentration (g/l); X, cell mass concentration (g/L); Y_P/S, process product yield (g lipid/g substrate); Y_P/X, specific yield of lipid (g lipid/g cells); Y_X/S, cell yield coefficient (g cells/g substrate); µ, specific growth rate coefficient (1/d); µ_max, maximum specific growth rate (1/d).