Abstract
The kinetics of lipid extraction utilizing microwave-assisted extraction (MAE) from Nannochloropsis sp. microalgae were studied using a low cost and green solvent, namely brine (NaCl) solution. The kinetic modelling of the lipid extraction was performed to evaluate the mechanism of the lipid mass transfer using different extraction models, including Fick’s Law, First and Second-order Rate Law and the Patricelli mathematical model. The Patricelli mathematical model described the kinetics of lipid extraction well, with the highest average values of determination coefficient (R2 ≥ 0.952) and the lowest average values of mean relative percentage deviation (MRPD ≤ 8.666%). The lipid analysis indicated a positive influence of the microwave temperature and time on the quantity and quality of extracted lipids. SEM analysis of spent microalgae clearly shows an increase in the distorted cell with increase microwave temperature and time, which could be directly correlated to the mechanism of the MAE-brine technique.
Highlights
Nannochloropsis sp. microalgae are considered a promising microalga for the pharmaceutical industry due to its high lipid content with high levels of polyunsaturated fatty acids (PUFAs), especially omega-3 eicosapentaenoic acid (EPA) [1]
The kinetic experiments were conducted for 30 min using microwave-assisted extraction (MAE)-brine solvent under the previously obtained optimum extraction conditions [6]
The results show an increase in the lipid yield with increasing extraction time and this is more prominent at higher temperatures
Summary
Nannochloropsis sp. microalgae are considered a promising microalga for the pharmaceutical industry due to its high lipid content with high levels of polyunsaturated fatty acids (PUFAs), especially omega-3 eicosapentaenoic acid (EPA) [1]. There are several steps involved in microalgal lipid production, namely cultivation, harvesting, lipid extraction, separation and later, FA purification. Among these steps, the lipid extraction step is a crucial step for enhancing the quality and quantity of lipid production from microalgae [2]. The microwave-assisted extraction (MAE) technique has enormous potential as a promising method for microalgal lipid extraction, as it is non-intricate and eco-friendly [3], and useful for lipid extraction due to the high heating rate [3], minimal amount of solvent usage [4], lower operating cost and fast extraction time [5]. The mass transfer parameters of lipid extraction from microalgae via conventional techniques have been explained through thermodynamic and Molecules 2020, 25, 784; doi:10.3390/molecules25040784 www.mdpi.com/journal/molecules
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