Abstract: The present invention provides a photobioreactor for a phototrophic microorganism, and culture medium therefor, comprising a capsule, the capsule comprising an elongated body comprised of a first, flexible polymer film that is at least partially transparent to light of a wavelength that is photosynthetically active in a phototrophic microorganism and divided width wise into a plurality of adjacent channels, each channel having a major cross-sectional dimension that is not more than about one-third of the length of the elongated body, when the elongated body is inflated; and a fluid distribution structure coupled to the elongated body adapted for fluid communication with the plurality of adjacent channels that distributes a flow of culture medium amongst the plurality of channels, wherein the fluid distribution structure is comprised of a second, flexible polymer film.