The photolithotrophic cultivation of a novel cell suspension culture derived from the microscopic, filamentous gametophyte life phase of the complex brown alga Laminaria saccharina was feasible in an illuminated bubble-column bioreactor at 13 degrees C using CO2 in air as the sole carbon source for growth. Maximum cell densities exceeding 1,000 mg dry cell weight (dcw) l(-1) and specific growth rates of 0.15 day(-1) were attained within a 20-day cultivation period initial cell density had a significant effect on the final biomass density of the clumped cell suspension but no significant effect on the specific growth rate. Although the optimum aeration rate for culture growth was 1.0 l air min(-1) l(-1) culture (vvm), the culture was not CO2-transport limited at 0.17-2.0 vvm. initial nitrate concentrations at or above 63.5 mg NaNO3 l(-1) in the GP2 artificial seawater medium had no significant effect on the specific growth rate or final biomass density. Both specific growth rate and final biomass density data were correlated to incident light intensity over the range of 1-91.2 mu E m(-2) s(-1) using an exponential model for light-saturated growth where light-saturated growth was achieved within a low-incident light intensity of 20 mu E m(-2) s(-1).