Enhanced waste glycerol recycling by yeast for efficient biodiesel production: Towards waste biorefinery

The present study aimed to evaluate a new oleaginous yeast for biodiesel production with high potential of lipid accumulation in waste glycerol as a carbon source. Seven strains were isolated and identified using 5.8S-ITS based on their ability to assimilate glycerol. Naganishia diffluens CDU-M7rc showed the maximum lipid productivity (LP) of 881.9 mg L-1 d(-1) at 96 h. Further optimization of pretreated waste glycerol (PWG) concentration enhanced the biomass yield to 20.3 g L-1 using 100 g L(-1)PWG and enhanced lipid content to 34.36 dw% at 120 g L(-1)PWG. However, the highest LP of 1.704 g L(-1)d(-1) was recorded at 100 g L-1 PWG, which represented 2.2-time more than the control. Using glucose as a carbon source, the dominant fatty acids in N. diffluens CDU-M7rc lipids were C16:0, C18:1, and C18:2, representing 23.91%, 55.45%, and 13.46% of total fatty acids, respectively. Utilization of PWG enhanced the proportion of C16:0 (33.39% of total fatty acids), with simultaneous reduction in C18:1 (41.12% of total fatty acids). Thus, supplementation of PWG enhanced saturated fatty acids proportion, which resulted in 10.8% reduction in the unsaturation degree of the produced biodiesel. All studied biodiesel characteristics showed acceptable values with the biodiesel international standards.