High-density algal photobioreactors using light-emitting diodes.

Lack of high-density algal photobioreactors (PBR) has been a limitation in exploiting the biotechnological potential of algae. Recent developments of highly efficient light-emitting diodes (LED using gallium aluminum arsenide chips) have made the development of a small LED-based PBR possible. We have calculated theoretical values of gas mass transfer requirements and light-intensity requirement to support high-density algal cultures for the 680 nm monochromatic red light from LED as a light source. A prototype PBR has been designed based on these calculations. A cell concentration of more than 2 x 10(9) cells/mL (more than 6.6% v%sol;v), cell doubling times as low as 12 h, and an oxygen production rate as high as 10 mmol oxygen/L culture/h were achieved using on-line ultrafiltration to periodically provide fresh medium. (c) 1994 John Wiley & Sons, Inc.