OPTIMIZATION OF ULTRASOUND-INDUCED MICROALGAL LIPID RECOVERY

The objective of this work was to optimize the operating parameters of ultrasound for inducing cell disruption and lipid recovery of a marine alga (Nannochloropsis oculata). Based on response surface methodology (RSM) experiments, a second-order polynomial model was developed to examine the effects of sonication duration (SD), power input (PI), and cell concentration (CC) on Nile red stained lipid fluorescence density (NRSLFD) per cell. The results showed that there was a positive stoichiometric relationship between SD and PI, but negative correlations existed between SD and CC and between PI and CC, suggesting that low CC was desirable for increasing NRSLFD per cell. The predicted maximum NRSLFD per cell was 1.25 x 10(-4), which was in close agreement with the measured NRSLFD of 1.15 x 10(-4) at SD of 3.42 min, PI of 364 W, and CC of 1.20 x 10(7) cells mL(-1). In addition, the recoverable crude lipids at the predicted optimal conditions for maximum NRSLFD per cell accounted for 74.5% of total lipid content. Long-chain and unsaturated lipids were degraded into short-chain and saturated lipids with ultrasonic cavitation.