Candida zeylanoides QU33: process for biodiesel production

Biodiesel production is increasing worldwide to supply a demand for renewable, environmentally-friendly fuels. In this sense, microbial oils appeared as potential feedstock for biodiesel production with scientific and commercial interest. While yeast oils have been studied for decades, recent years showed literature suggesting optimization of cultivation processes as a good strategy to improve lipid accumulation in oleaginous yeasts. Some factors, like carbon nitrogen (C/N) ratio, pH and temperature are considered as the main parameters that affect the production of microbial oil. This study aimed to improve the optimization of cultivation process through multivariate analysis, increase the lipid accumulation and transform the condition non-oleaginous to an oleaginous condition in Candida zeylanoides QU 33. For optimization, response surface methodology was applied, using the levels of the variables temperature (20-35ºC), pH (2.0 to 6.0), and glucose concentration (10-40 g/100mL). The results showed two adjusted models to improve biomass production and lipid yield in C. zeylanoides QU 33, where temperatures lower than 28ºC, and glucose concentrations greater than 25% are favorable for the accumulation of lipids. The concentrations of glucose lower than 15% were unfavorable. The best conditions were observed in the experiment at 27.5 °C, pH 6 and 25% (w/v) glucose, with a lipid yield of 0.2 g/L and lipid content of 12.42% (g/g). Besides the unsatisfactory effort to change the oleaginicity condition for C. zeylanoides QU 33, our results confirmed the hypothesis to use this strain as a model of lipid metabolism for non-oleaginous yeast.