Development of a culture protocol for Rhodomonas sp. Hf-1 strain through laboratory trials

Rhodomonas sp. Hf-1 is a marine microalgal strain with a high nutritional value. In order to produce this microalga effectively and inexpensively in a hatchery, its production protocol was reexamined through several culture trials. Firstly, it was found that the Hf-1 strain required nitrogen, phosphorus, iron, manganese and vitamin B12. The optimal nitrogen source was urea. Based on these results, a new medium, MU–SW, was formulated from agricultural fertilizers. Secondly, MU–SW medium was verified at production scale, in which satisfactory growth of the Hf-1 strain was obtained. The cell density reached approximately 3.0 × 106 cells ml−1, and five harvest cycles at 4-day intervals could be achieved. The high unsaturated fatty acid content of the harvested cells fluctuated in the following ranges: C18:2n-6, 19.8–25.2%; C18:3n-6, 8.7–15.2%; C20:4n-6, 2.0–4.6%; C20:5n-3, 8.2–11.3% and C22:6n-3, 5.6–7.3%. This study provides the baseline conditions for introducing the Hf-1 strain into an aquaculture food chain.