High-throughput screening for heterotrophic growth in microalgae using the Biolog Plate assay

Microalgae produce a broad range of organic compounds that are increasingly being recognised for their value in novel product production and biotechnological applications. Most microalgae are photoautotrophic, but some are capable of either mixotrophy or heterotrophy. Reported enhanced biomass yields or contrasting metabolite profiles compared to autotrophic growth improve the economics of large-scale production of microalgae, which currently limits industrial applications. Here, the potential of a high-throughput method for the rapid screening of microalgal metabolism was assessed against 95 different carbon sources, using the cost-effective Biolog plate. Of the 5 microalgae tested, Desmodesmus communis (30 carbon sources) and Chlorella vulgaris (19 carbon sources) had the highest number of positive responses to carbon sources, whereas Chlorella sorokiniana had the most negative (toxic) response to the various carbon sources (77 carbon sources). Comparison of Biolog plate results with traditional culture techniques showed good agreement. Species with a high number of positive responses on the Biolog plate exhibited the highest biomass yield under heterotrophic conditions, whilst those with low number of positive responses exhibited the highest biomass yield under autotrophic conditions, using traditional culturing techniques. While the use of these plates is limited to obtaining axenic lines of microalgal species, the method provided a high-throughput assessment of carbon source metabolism, without the expense of undertaking large, laborious traditional culturing assessments. Such high-throughput assessments can be regarded as useful tools for progressing species selection, metabolic capacity and optimal culture conditions for microalgal biotechnology applications.