Microbial Oil Production by Yarrowia lipolytica Under Semi-Continuous Cultivation and Potential Utility of Spent Supernatant

Microbial oil production has gained attention as a sustainable and cost-effective alternative to conventional vegetable and fish oils. Among oleaginous microorganisms, Yarrowia lipolytica is notable for its ability to accumulate lipids exceeding 20% of its dry weight. This study aimed to evaluate semi-continuous cultivation as a strategy for sustainable microbial oil production by Y. lipolytica, while also assessing the potential utility of the spent supernatant. Three different feeding frequencies were evaluated. In the 24 h feeding regime, the maximum oil concentration reached 11.22 g/L, decreasing to 8.43 g/L by the 88th hour. In the 6–6–12 h feeding strategy, crude protein content peaked at 43.75% of dry mass at 22 h. Fatty acid profiling revealed consistently low saturated fatty acid (SFA) levels (4.93–10.30%), while unsaturated fatty acids (UFA) dominated (89.69–95.05%). Monounsaturated fatty acids (MUFA) were predominant, reaching up to 81.24%, whereas polyunsaturated fatty acids (PUFA) ranged from 20.78% to 29.98%. Oleic acid was the most abundant fatty acid across all conditions. This composition supports the potential of microbial oil from Y. lipolytica as a sustainable alternative edible lipid ingredient for human food applications, complementing conventional plant-based oils. The favorable unsaturated fatty acid profile indicates its potential suitability for incorporation into food formulations requiring nutritionally desirable lipid sources. As part of the sustainability-oriented approach of the study, the freeze-dried post-culture supernatant was also evaluated for its potential further utilization. With a calorific value of 10.43 kJ/g and significant phosphorus and potassium levels, it shows potential as a biofuel feedstock and as a biofertilizer or biostimulant.