Culture of the blue-green algae Spirulina in order to harvest the blue-green pigment phycocyanin in outdoor ponds results in poor yield and biological contaminants. The invention discloses methods and systems for culturing microorganisms under red light (optimum emission wavelength of 680 nm) that result in increased cellular and media concentrations of the biological pigment compared with the same microorganism cultured under white light. The invention has applications in use as a natural food colouring, as antioxidants in the food supplement industries, in the nutraceutical, pharmaceutical, and cosmeceutical industries, and a non-toxic ink. The method results in pigment that is relatively easy to separate from the microorganism culture.
