Photosynthetic cyanobacteria, when harnessed in a photobioreactor or solar collector, can convert atmospheric carbon dioxide and light energy into usable biofuels; unfortunately, current photobioreactors produce uneven illumination at low densities, minimizing efficiency of the biofuel conversion process. But researchers at the University of Victoria (Victoria, BC, Canada) and Cornell University (Ithaca, NY) have discovered that near-field evanescent waves on the surface of waveguides generated by a helium-neon (HeNe) laser can stimulate the thylakoid membranes of cyanobacteria responsible for light-dependent photosynthesis reactions. This approach has the potential to optimize the production of biofuel and minimize harmful photobleaching of cyanobacteria species.
To demonstrate feasibility, the pill-shaped, immotile cyanobacteria Synechoccocus elongatus was cultured on a microscope slide and placed over a right-angle prism through which was passed a 1 mW, 632 nm HeNe laser beam. Contained in a dark enclosure, total internal reflection induced an evanescent profile that was highest in the center of the ellipse and decreased toward the periphery. The region just outside the central Gaussian beam (and beyond the region of highest illumination at 500 W/m2, which results in photo-inhibition of the cells and stunted growth) showed preferential growth of the cyanobacteria species. A plasmonic excitation scheme is under development using an optically thick layer of gold to minimize the influence of directly transmitted light. Contact Matthew Ooms at [email protected].