Microbial Oils from Tropical Fruit-Derived Oleaginous Yeasts: Lipid Profiles and Predicted Biodiesel Potential

Microbial oils produced by oleaginous yeasts are promising renewable lipid resources for biofuel and other biotechnological applications. Tropical fruits may harbor diverse yeasts with the capacity to accumulate intracellular microbial oils, but their lipid profiles and biodiesel-related characteristics remain insufficiently characterized. This study aimed to isolate and screen oleaginous yeasts from tropical fruits in Thailand and evaluate their intracellular microbial oil accumulation, fatty acid composition, and predicted biodiesel-related properties. A total of 56 fruit-derived yeast isolates were screened using Sudan IV staining, followed by gravimetric determination of intracellular microbial oil content. Eleven isolates were Sudan IV-positive, of which two were classified as oleaginous based on lipid contents exceeding 20% of dry biomass. These isolates were identified as Pichia kudriavzevii strain SA(I)02 and Candida tropicalis strain PSM(I)01, with microbial oil contents of 29.953% and 40.622%, respectively. Their fatty acid profiles differed markedly, with P. kudriavzevii showing higher MUFA content, particularly oleic acid, whereas C. tropicalis exhibited a higher proportion of saturated fatty acids. Consequently, P. kudriavzevii showed a higher predicted degree of unsaturation and a lower long-chain saturated factor, while C. tropicalis showed a higher predicted cetane number and a higher long-chain saturated factor. These findings show that lipid accumulation capacity and fatty acid composition are distinct characteristics that should be considered together when evaluating oleaginous yeasts for potential biodiesel applications.