Ultrasonication pre-treatment techniques on microalgae Chlorella vulgaris & Nannochloropsis oculata for lipid extraction for biodiesel production

Sumptuous nutritious products and biofuels could be produced from microalgae. Their applications include in various sectors like food, medical, and energy industries, etc. Microalgal cell disruption is viewed an important aspect for the production process. Cell disruption aids in the extraction of the bio-products stored within them. Lipids are the most commonly extracted compounds from microalgae, and they have a higher tendency in biodiesel production. In this study, the following ultrasonic pre-treatment conditions are applied on two different microalgae chlorella vulgaris & nannochloropsis oculata with differing frequencies (37 and 80 kHz), exposure time (10,15 and 20 mins) and extraction time (2, 3 and 4 hrs) were investigated. In addition, the ultrasonic frequency generates acoustic cavitation to break their cell wall and extract lipids. The results show that a good amount of lipids can be disrupted and recovered from microalgae by using an increased frequency. The highest lipid yield extraction of 11.52% (chlorella vulgaris) and 17.91% (nannochloropsis oculata) are obtained. The transestrified oil was used to produce biodiesel feedstock and the results of gas chromatography were also discussed.