Comparative study for extraction and characterization of oil from Nannochloropsis sp. and Spirulina sp. using Folch method and Soxhlet method

Microalgal oil is an important source of high-value fatty acids. However, the quality and extraction yield is often affected by the oil extraction process. The quality of oil extracted decides its end use as biofuel or neutraceuticals. This study investigated the effect of two different extraction methods viz. Folch method and Soxhlet method on the quality as well as extraction yield of the oil from Nannochloropsis sp. and Spirulina sp. The chemical parameters of oils such as acid value, free fatty acid, peroxide value, and iodine value as well as the oil fatty acid composition analysis were carried out. The oil obtained from Soxhlet extraction showed lower acid value, free fatty acids content, and peroxide values in both species compared to the Folch method. However, the oil recovery (% oil yield) was higher (22% and 8%) in the Folch method as compared to the Soxhlet method (11% and 6%) from Nannochloropsis sp. and Spirulina sp. respectively. The fatty acid composition showed higher content of long-chain omega-3 fatty acids when extracted using Soxhlet method viz. 0.66% and 2.52% of EPA and DHA compared to 0.46 to 0.50% of EPA and DHA by Folch method from Nannochloropsis sp. and Spirulina sp respectively. The outcome of the study justifies the Soxhlet method of oil extraction as a superior method for oil extraction from microalgae with good quality and stability. Oil obtained in this way could be used in the food, feed and oil industry.