silica powder was added to the extr

silica powder was added to the extraction system to increase the shear stress induced to the microalgae cell. the results showed that the addition of silica powder did not increase the extraction of oil. in fact, the addition of silica powder had a negative effect in the extraction process. it was expected that the intense local turbulence in the medium created by ultrasound would help mixing the silica powder, which in turn would increase the shear stress induced to the microalgae cell wall. the result suggest that the presence of silica powder reduced the effect of ultrasound, leading to a lower extraction of oil.