Bioconversion of commercial and crude glycerol to single-cell oils by the Antarctic yeast Rhodotorula glutinis R4 as a biodiesel feedstock

Abstract

Ability of the oleaginous yeast Rhodotorula glutinis R4 to produce single-cell oils (SCO) using different concentrations (25–100 g L−1) of commercial and crude glycerol as substrate was evaluated. R. glutinis R4 reached 44–57% and 41–52% (w/w) of lipid accumulation when grown with 25–100 g L−1of crude and commercial glycerol, respectively. R4 grown with 35 and 50 g L−1 of crude glycerol reached a lipid accumulation of 44–45% (w/w) at 120 h corresponding to 6 g L−1 of lipid concentration, with a yield YL/S ∼ 0.45 g g−1, lipid productivity (QL) of 0.05 g L−1h−1, and a glycerol consumption of 31 and 37.2 g L−1, respectively. Regarding the volumetric productivities at the different concentrations, the QL (0.05 g L−1 h−1) and QX (0.11 g L−1 h−1), did not differ statistically from the control (glucose). Lipid accumulation was higher at 216 h of culture using 100 g L−1 of glycerol (51 and 57% for commercial and crude, respectively), but a significant decrease of QL (from 0.05 to 0.03 g L−1 h−1) and Qx (0.11 to 0.09 g L−1 h−1) was observed. A negative effect on yield, Qx and QL was observed at glycerol concentrations above 50 g L−1. R4 SCO showed a fatty acid profiles rich in oleic acid and suitable for biodiesel production, and were efficiently transformed into biodiesel with yields above 90% by acid transesterification. Biodiesels derived from R4 using crude glycerol are fully complies with international biodiesel standards. This allows advance in a process of circular economy for biodiesel industry.