Beneficial changes in biomass and lipid of microalgae Anabaena variabilis facing the ultrasonic stress environment

This study investigated the beneficial effects of ultrasonic treatment on the biomass, lipid and protein of the microalgae Anabaena variabilis. The microalgae after 11 days cultivation (initial algae) were treated at the powers of 200, 350 and 500 W for 10 min and then cultured continuously for 3 days (day 12-14). The power of 200 W induced the highest lipid content 37.8% on day 12. The subsequent experiments tested the ultrasonic treatment times of 5, 10, 20 and 40 min at 200 W in the initial algae. The significantly improved lipid content 46.9% and productivity 54.2 mg/L/d were obtained almost 1.46 and 1.86 times more than that of the control algae respectively after 1 day of continuous cultivation at 5 min. The proper ultrasonic treatment showed the feasibility and high efficiency in promoting lipid accumulation without negatively influencing the biomass, fatty acid profiles and protein content.