Only a few reports available about the assimilation of hydrophobic or oil-based feedstock as carbon sources by Lipomyces starkeyi. In this study, the ability of L. starkeyi to efficiently utilize free fatty acids (FFAs) and real biomass like palm acid oil (PAO) as well as crude palm kernel oil (CPKO) for growth and lipid production was investigated. PAO, CPKO, and FFAs were evaluated as sole carbon sources or in the mixed medium containing glucose. L. starkeyi was able to grow on the medium supplemented with PAO and FFAs, which contained long-chain length FAs and accumulated lipids up to 35% (w/w) of its dry cell weight. The highest lipid content and lipid concentration were achieved at 50% (w/w) and 10.1 g/L, respectively, when L. starkeyi was cultured in nitrogen-limited mineral medium (-NMM) supplemented with PAO emulsion. Hydrophobic substrate like PAO could be served as promising carbon source for L. starkeyi.
The ability of oleaginous yeast Lipomyces starkeyi to efficiently produce lipids when cultivated on sap extracted from felled oil palm trunk (OPT) as a novel inexpensive renewable carbon source was evaluated. OPT sap was found to contain approximately 98 g/L glucose and 32 g/L fructose. Batch fermentations were performed using three different OPT sap medium conditions: regular sap, enriched sap, and enriched sap at pH 5.0. Under all sap medium conditions, the cell biomass and lipid production achieved were approximately 30 g/L and 60% (w/w), respectively. L. starkeyi tolerated acidified medium (initial pH ≈ 3) and produced considerable amounts of ethanol as well as xylitol as by-products. The fatty acid profile of L. starkeyi was remarkably similar to that of palm oil, one of the most common vegetable oil feedstock used in biodiesel production with oleic acid as the major fatty acid followed by palmitic, stearic and linoleic acids.