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

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-1 of 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 Y-L/S similar to 0.45 g g(-1), lipid productivity (Q(L)) of 0.05 g L(-1)h(-1), and a glycerol consumption of 31 and 37.2 g L-1, respectively. Regarding the volumetric productivities at the different concentrations, the Q(L) (0.05 g L-1 h(-1)) and Q(X) (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 Q(L) (from 0.05 to 0.03 g L-1 h(-1)) and Q(x) (0.11 to 0.09 g L-1 h(-1)) was observed. A negative effect on yield, Q(x) and Q(L) 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.