New microalgae media formulated with completely recycled phosphorus originating from agricultural sidestreams

Abstract

This study investigated the impact of struvite as a sustainable phosphorus source on the growth and phycocyanin production by the blue-green alga Arthrospira platensis. Three modified growth media were compared to the typical SAG-spirul culture media. CS(+) refers to the completely recycled struvite from bovine urine as a phosphate source, while S(-) and S(+) refer to commercially available struvite as a phosphate source. On media with (+), a pre-treatment was conducted to evaporate NH4, as it negatively affects cell growth and functions of the photosynthetic apparatus at high concentrations, and to release phosphate due to the low solubility of struvite in water. For each medium, three cultures were cultivated in Erlenmeyer flasks for a duration of 42 days. Results showed that no statistically significant negative effect of struvite was found on the growth rates. However, C-phycocyanin (CPC-P) in CS(+) and S(+) was significantly higher compared to CPC-P in untreated growth media. The study hypothesized that low concentrations of NH3 remaining after the pre-treatment of struvite could have a positive impact on phycocyanin accumulation, as an energy efficient and quick nitrogen source for A. platensis.