Rapid estimation of protein, lipid, and dry weight in microalgae using a portable LED fluorometer

As the industry surrounding microalgae continues to develop, there is a growing need for reliable, ready-to-use technologies for measuring the growth and composition of algal cultures. These can be new technologies or adapted existing technologies presently used for similar applications in other systems. Here we demonstrate the use of an LED fluorometer for the rapid estimation of dry weight, protein, and lipid content from two strains of microalgae. The instrument was successfully used to determine the dry weight of Chlamydomonas reinhardtii (CC-3491) and Scenedesmus dimorphus (UTEX 1237) cultures, at densities up to 1.58 g/L. Soluble protein was also measured using the instrument, and was highly comparable (average within 3%) to results obtained using both the Bradford and Lowry methods. Lastly, neutral lipid accumulation induced by nitrogen starvation was estimated via BODIPY 495/505 fluorescence. The basic methods developed here can easily be applied to any strain of microalgae or cyanobacteria, and demonstrate reliable, cost-effective, single-instrument methods for the determination of several key parameters in the cultivation of photosynthetic microorganisms.