Usage potential of apple and carrot pomaces as raw materials for newly isolated yeast lipid-based biodiesel production

It is vital to determine the novel oleaginous yeasts for biodiesel production, and lignocellulosic by-products have various advantages as growth media for microbial lipid production. By this context, in this study, lipid accumulation capacities and biodiesel production potentials of two newly isolated yeasts (Candida albicans and Kluyveromyces marxianus) were investigated. Sustainable agricultural wastes such as carrot and apple pomaces were used for lipid accumulation experiments. Some critical parameters such as pH (3-6), initial pomace loading (6%-12%), nitrogen type (soy wheat, urea, whey, KNO3, NH4NO3, and NH4Cl), and concentration (0.25-1.5 g/L) of nitrogen sources, incubation time (24-96 h), and solvent type in lipid extraction (n-hexane, chloroform:methanol, chloroform, methanol, and ethanol) were optimized. The maximum lipid concentrations and total C16 + C18 fatty acid methyl ester yields were found as 41.3% and 74.1% for C. albicans and 37.8% and 84.6% for K. marxianus, respectively. Because of some critical fuel properties of the fatty acid methyl esters such as cetane number, kinematic viscosity, and iodine value that were matched well with ASTM D6751 and EN 14214 standards, this study shows that apple and carrot pomaces are promising feedstocks for yeast lipid-based biodiesel production.