Abstract: Selenium-enriched Spirulina platensis (Se-SP) was cultured in osmotic membrane tube (OT) and compared with air blowing bioreactor (AB) and shaking bottle (SB) cultures under the same conditions. Se supplementation was 100 μg/mL in the form of sodium selenite. Growth rate and maximum biomass were monitored and deduced according to dry weight at designated time points. Total Se, organic Se and inorganic Se in Se-SP as well as soluble and insoluble Se species in culture medium were determined using a fluorimeter. Total protein (TP), phycocyanin (PC), chlorophyll a (Chla), carotenoids (Caro), total polysaccharides (SPS) and sulfydryl groups (-SH) in Se-SP were also detected colorimetrically. The contents of inorganic carbon (IC) and dissolved organic carbon (DOC) in culture medium were measured using a TOC-5000A analyzer. The results showed that the maximum biomass of Se-SP was up to 9.6 g/L during cultivation in OT tube, which was increased by 3－5 fold compared with AB and SB cultures. The conversion rate of organic Se and the contents of TP, PC, Chla, SPS and SH group in Se-SP from OT culture were significantly higher than those from AB and SB cultures. Accordingly, OT culture produced lower IC residues and less accumulation of DOC, and higher soluble Se in the conditioned culture medium. In conclusion, OT can be used as a novel material for high cell density culture of Se-PS and it will have the advantages of high cell proliferation rate, high biotransformation of organic Se, high consumption of inorganic nutritional sources, low accumulation of organic carbon and less release of waster water.

Key words: Spirulina platensis, selenium, high density culture