Single-Cell and Systems Biology Tools for Biofuel Production

Abstract

Microalgae, a promising biomass feedstock for renewable biofuels, efficiently adapt lipid and carbohydrate metabolism in response to environmental changes and produce a variety of biofuel molecules including triacylglycerol (TAG) and starch. During such bioprocesses, cell-to-cell variation of phenotypes has been shown to be crucial for the cells to adapt to the fluctuating environments. Therefore, rapid, real-time and label-free measurements of such biofuel molecules at single-cell resolution are of importance for bioprocess monitoring, control and engineering. Single-cell Raman microspectroscopy can directly detect the change of metabolite profiles in a cell in a non-invasive manner and thus is potentially valuable for these purposes. In this protocol, we show that single-cell Raman spectra (SCRS) can serve as a proxy for quantitatively tracking and screening TAG/starch content at single-cell level. This methodology can screen a large number of cells in a relatively short time and reveal the phenotypic heterogeneity of cells within an isogenic population. Moreover, the measurement, performed at single-cell resolution, does not necessarily require cultivation and thus can be useful for discovery and excavation of novel synthetic-biology parts, modules and cells of bioenergy applications from the vast yet-to-be-cultured microbiota in nature.

*These authors are co-first-authors, i.e., they contributed equally.