Selection of Marine Microalgal Strains for Biodiesel Production by Flow Cytometry

Researchers from the Division of Environmental Science and Engineering, Faculty of Engineering, National University of Singapore, investigated the possible strains of marine microalgae which could be used in biodiesel production. Microalgae have been considered as the more sustainable feedstocks for biodiesel production (compared to terrestrial bioenergy crops) because of their high oil content and rapid biomass production. Marine microalgae are particularly considered to have an advantage over freshwater microalgae as biodiesel feedstocks, because they do not require freshwater during cultivation (i.e. lower "(fresh)water footprint").

In their paper, the researchers presented a screening procedure for the selection of the favorable microalgae cell biodiesel feedstock. First, microalgae cells were sorted using an automated flow cytometric cell sorting technique. The technique is based on the two-dimensional distribution of algal cells for red fluorescence (chlorophyll auto-fluorescence) against forward-light scatter (cell size) and red vs. green fluorescence. Using the technique, the researchers were able to isolate ninety six strains of marine microalgae with favorable characteristics (elevated biomass productivity and intracellular lipid content) from the coastal waters of Singapore. 

Further characterization for the selection of the best biodiesel feedstock was done with respect to cell growth rate, biomass concentration, lipid (total and neutral lipid) and fatty acid profile. The researchers reported that the Skeletonema costatum, Chaetoceros and Thalassiosira species have the highest growth rate. However, they found that the most promising species for biodiesel production were the Nannochloropsis strains, because these strains had the highest lipid content, ranging from 39.4% to 44.9% of the dry biomass. Biodiesel production from the transesterification of the lipids of the Nannochloropsis strains yielded 25-51% of fatty acid methyl esters (FAME). This translates to 11% to 21% FAME content of dry biomass.

The full study is published in the free access journal, Biomass and Bioenergy (URL above). Related information on flow cytometry: http://probes.invitrogen.com/resources/education/tutorials/4Intro_Flow/player.html.