Rapid transesterification of micro-amount of lipids from microalgae via a micro-mixer reactor.

Fatty acid composition is an important physiological parameter of microalgae, which is taken as the third generation alternative resource of biodiesel. To boost microalgal research and applications, a convenient, rapid, and acid-catalyzed transesterification procedure that satisfies the demand for the analysis of the fatty acid composition of lipids with micro-scale samples in the high-throughput screening of microalgal strains is needed, along with the evaluation of the physiological status of microalgae in response to nutrient stress. The reaction conditions of transesterification via a micro-mixer reactor were optimized as follows: 90 °C reaction temperature, 20 min reaction time, 6:1 volume ratio of H2SO4-methanol to lipid-in-hexane, and a Y-type micro-mixer with a 20-m-long extended loop that has a 0.3 mm diameter. The minimum amount of sample was decreased to 30 µg lipids. The new approach was successfully applied to the fatty acid composition analysis of soybean oil and microalgal lipids. Definitely, it could be applied to acyl related oils from different sources. Here, we have developed a simple and rapid method for the analysis of the fatty acid composition of lipids. The new method requires less than 20 min for transesterification and a minimum of only 30 µg lipid sample. Furthermore, a high-throughput process can be easily realized by numbering up the micro-mixer reactors. The micro-mixer reactor has great potential for applications not only in large-scale biodiesel production but also for the micro-scale analysis of microalgae fatty acid compositions.