Abstract: Penicillium citrinum Asc2-4 is the oleaginous fungus isolated from Pyrosomella verticilliata. In this study, the effects of single factors such as temperature, pH, inoculation amount, rotational speed and liquid volume on the growth and oil production of the fungus were investigated. The significant factors of high-yield oil were then optimized by response surface method, and lastly the composition of oil was analyzed by gas chromatography. The result showed that single factor optimization preliminarily determined the suitable fermentation conditions for fungal growth. The significant factors for the improvement of oil production included inoculation amount, liquid loading amount and rotational speed. The optimal fermentation conditions obtained by response surface method showed the temperature 29 ℃, pH 5.5, inoculation amount 3.3%, liquid volume 120 mL/250 mL, and rotational speed 220 r/min. The verification results were consistent with the predicted values of the model. Biomass and lipid mass concentration reached 19.19 g/L and 8.80 g/L, which were 65.57% and 224.72% higher than those before optimization, respectively. The C16 and C18 fatty acids in fungus oil accounted for 96.26% of the total fatty acids, and the components thereof, encompassing 41.52% oleic acid (C18:1), 21.74% linoleic acid (C18:2), 16.77% palmitic acid (C16:0) and 15.61% stearic acid (C18:0). This study provided theoretical basis for the development and utilization of Penicillium citrinum Asc2-4.

Key words: Pyrosomella verticilliata, Penicillium citrinum, oleaginous fungi, fermentation condition, fatty acid composition