Iron chelating agents and their effects on the growth of Pseudokirchneriella subcapitata, Chlorella vulgaris, Phaeodactylum tricornutum and Spirulina platensis in comparison to Fe- EDTA

The industry standard iron source for algae culture is in most cases Ethylenediaminetetraacetic acid ferric sodium salt (Fe-EDTA). During algae production pH and light intensity are not favorable for maintaining the integrity of the Fe-EDTA complex. As a consequence, iron availability becomes the limiting factor for growth. A series of growth studies and biomass determinations with a selection of alternative iron chelating agents were conducted under controlled conditions. Fe-EDTA was used as the control iron source to determine if any potential advantages of the test chelates could be identified. Results demonstrated slower initial growth in short term tests for chelating agents with higher stability constants than Fe-EDTA and similar results for iron chelating agents with a similar or lower stability constant. Considerable long term improvements in algae growth during extended studies (>7 days) with Chlorella vulgaris and Spirulina platensis were observed for higher stability chelates. Optimization of the iron source with chelating agents that have better pH and light stability can delay the onset of iron limiting conditions. Advantages to commercial batch processes such as increasing the growth between cleanouts, elevating lipid and biomass production and possible savings of raw materials are potentially achievable with optimized iron chelation.