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.
Yeast growth and biomass production are greatly influenced by the length of the
incubation period during cultivation. Therefore, this study was conducted to
investigate the growth kinetics of five Lipomyces starkeyi strains as determined by
biomass production. The five L. starkeyi strains, namely L. starkeyi ATCC 12659, L.
starkeyi MV-1, L. starkeyi MV-4, L. starkeyi MV-5 and L. starkeyi MV-8, were inoculated
in sterilized Yeast Malt broth, and, incubated for 192 hr at ambient temperature.
Biomass yields were assessed and calculated gravimetrically every 24 hr. Results
indicated that the optimal biomass production of L. starkeyi ATCC 12659, L. starkeyi
MV-1, L. starkeyi MV-4, L. starkeyi MV-5 and L. starkeyi MV-8 were at 120, 168, 144,
168 and 120 hr, with the concentrations of 6.64, 6.43, 9.78, 11.23 and 8.56 g/L,
respectively. These results indicate that each L. starkeyi strain requires specific
incubation period for the optimum production of fungal biomass. Therefore, by
cultivating each L. starkeyi strain at the predetermined incubation period, biomass
yields could significantly be improved for further downstream applications such as
single cell protein and lipid production.