Prediction of lipid accumulation-degradation in oleaginous micro-organisms growing on vegetable oils.

Oleaginous micro-organisms (yeasts, moulds), in culture media having the carbon source as limited factor, degrade reserve lipids and produce new biomass, after the onset of carbon exhaustion from the medium. In this paper the process of lipid accumulation-degradation in oleaginous micro-organisms, growing on a vegetable oil was simulated. The model was integrated with 4 different methods and the parameters were optimised with the least squares method. It was found that the degradation of endocellular carbon pool is a very slow process characterised, however, by a good yield in fat-free biomass. Low values of the specific growth rates of the fat-free microbial mass, both from consumption of extracellular and endocellular carbon pools, favourite the production of microbial lipid. The maximum of the specific rate of lipid accumulation is positively affected by the low values of the specific growth rate of the fat-free microbial mass from consumption of extracellular carbon pool, but remained unaffected by the specific growth rate of the fat-free microbial mass from consumption of endocellular carbon pool. On the other hand, lipid production and specific rate of lipid accumulation are positively influenced by the high values of the specific rate of storage lipid formation. In conclusion, this numerical model can be used in the laboratory as pilot for planing further experimental work.