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In order to conquer the block of high cost and low yields which limit to realize the commercialization of microalgal biodiesel, the mixotrophic and heterotrophic cultivation of Scenedesmus quadricauda FACHB-1297 fed on xylose was studied separately employing six forms of media: phosphorus su cient, phosphorus restricted and phosphorus starvation were combined with nitrogen su cient and nitrogen starvation conditions. The maximum oil percentage (about 41% of dry weight) was obtained on the 5th day (heterotrophic cultivation) and 8th day (mixotrophic cultivation) under the nitrogen starved and phosphorus su cient (N 0 &P) conditions, which was about 2-fold in comparison to the initial lipid content on the su cient nitrogen condition (control). Under mixotrophic and heterotrophic modes, the highest lipid productions were both achieved in the N 0 &P trial, with the value of 274.97 mg/L and 193.77 mg/L, successively. Xylose utilization rate of 30%-96% under heterotrophic modes was apparently higher than that of 20%-50% in mixotrophic modes. In contrast, phosphorus uptake rate of 100% under mixotrophic modes was signi cantly more than that of 60%-90% in heterotrophic cultivation. Furthermore, under xylose heterotrophic cultivation, the phosphorus had a positive impact on microalgae cell synthesis, and the oil content enhanced with the augmentation in phosphorus concentrations. We suggest that su cient phosphorus should be supplied for obtaining more microalgal lipid production in the lack of nitrogen for xylose heterotrophic and mixotrophic conditions. This is a highly effective way to obtain e cient microalgae biofats production.

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