solvent-free ultrasound-assisted extraction (UAE) is used to extract lipids from fresh Nannochloropsis oculata biomass. Through response surface methodology (RSM) parameters affecting the oil recovery should  optimize. Optimum conditions for oil extraction cab be estimated as follows: (i) 1000 W ultrasonic power, (ii) 30 min extraction time and (iii) biomass dry weight content at 5%. Yields are calculated by the total fatty acids methyl esters amounts analyzed by GC-FID-MS. The maximum oil recovery may around 0.21%. This is an effective extraction method adapted for microalgae oil recovery. Acoustic cavitation created by ultrasound tremendously facilitates solvent access through cell walls and promotes oil extraction. It also provides very efficient mixing of oil and alcohol, which speeds up the phase transfer-limited transesterification reaction. These effects occur due to the mechanical action of ultrasonic cavitation, which produces violently and asymmetrically imploding bubbles and causes micro-jets that pierce cell walls. High ultrasonic amplitudes, on the order of 70 - 120 microns peak-to-peak (below, microns), are necessary to maximize the efficiency of ultrasound-mediated extraction and transesterification. Conventional high-power ultrasonic technology, however, inherently forces all processes to run either at a small scale and high amplitude or a large scale and low amplitude, not allowing for the possibility of implementing high amplitudes on industrial scale.

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https://www.researchgate.net/publication/308357814_Optimization_of_Ficus_deltoidea_Using_Ultrasound-Assisted_Extraction_by_Box-Behnken_Statistical_Design

Article Optimization of Ficus deltoidea Using Ultrasound-Assisted Ex...