An integrated photobioreactor and foam fractionation unit for the growth and harvest of Chaetoceros spp. in open systems

The separation of cells from large volume cultures by centrifugation is a costly and time-consuming process that has prompted the exploration of alternative propitious separation strategies. Foam fractionation is a technique that can be used to concentrate large cell culture volumes, significantly decreasing centrifugation time requirements. A foam fractionation system is relatively inexpensive and easy to maintain. This study was aimed at empirically determining optimal levels of the major factors influencing foam fractionation of the marine diatom Chaetoceros spp. in a pilot scale, open culture, integrated photobioreactor and foam fractionation unit. The experimental system consisted of eight 2201 fiberglass photobioreactors that served as growth chambers and foam fractionating units. Bubble size, air flow rate (AFR), cell density (CD), overflow height (OH), pH and foam fractionation run time (RT) were factors investigated while harvesting the outdoor open cultures. Flocculating agents and surfactants were not added to the diatom cultures at any time. Experiments were conducted to determine how variable levels influence dry weight yield, harvesting efficiency (HE) and foam volume collected. Experimentally determined setpoints resulted in harvesting efficiencies exceeding 90% while extracting less than 12% of the total culture volume in a period of 30 min. These results indicate that foam fractionation is a practical tool for harvesting Chaetoceros spp. diatoms. (C) 2003 Elsevier B.V. All rights reserved.