Production of exocellular pigment by the marine diatom Haslea ostrearia Simonsen in a photobioreactor equipped with immersed ultrafiltration membranes

A new photobioreactor coupled with an ultrafiltration system (immersed memb ranes) was investigated for the continuous culture of the microalga Haslea ostrearia in order to improve pigment (marennine) production and recovery. The system presents a commercial interest, because energetic costs were min imized, and the cells were not submitted to any shear stress due to pumping or circulation. To obtain this, since the photobioreactor was of cylindric al type, a membrane module was placed at the bottom of the reactor and the hydrostatic pressure (the height of the water column) used as driving force both for the permeation and periodical backflushing steps. The production of biomass and marennine was stable for a three-week period, with marennine specific productivity approximate to 30-35 mg 10(-9) cell day(-1), marenni ne concentration approximate to 3 times higher than in a conventional batch photobioreactor. The permeation Aux obtained was acceptable (3-10 l h(-1) m(-2), 3 kPa, 15 degrees C), but for such applications, this type of integr ated process needs further improvements. Owing to its simple design, the co ncept "photobioreactor - ultrafiltration with immersed membranes" has good possibilities in biotechnology and aquaculture for continuous extraction of exocellular metabolites. (C) 2000 Elsevier Science Ltd. All rights reserve d.