Effect of land-based suspension conditions on the culture of the Rhodophyta Bangia fuscopurpurea

Abstract

Land-based suspension culture helps solving the problems faced by traditional marine-raft culture, such as uncontrollable environmental factors, limited breeding cycle, frequent disease and pest outbreaks, and high levels of impurities in cultured products. Bangia fuscopurpurea has a distinctive multi-row filamentous cell structure, which makes it ideal for suspension culture research. This study investigated the effects of different environmental factors —such as initial algal density, temperature, photoperiod, light intensity, nitrogen source and nitrogen-to-phosphorus ratio, ferric citrate, and salinity— on the growth of suspension-cultured B. fuscopurpurea for the first time. We also evaluated the nutritional content under different aquaculture modes and determined the optimum approach for removing epiphytic algae. Relative daily growth rates were significantly affected by temperature and N concentration, with the highest value (15.85 ± 0.74 % d⁻¹) observed under conditions of 18°C, 12 L:12D photoperiod, 100 μmol m⁻² s⁻¹ light intensity, and N/P ratio 16:1 with NO₃⁻–N. The breeding cycle was shortened to 6–9 days from 10–15 days typical of traditional marine-raft culture. Protein and crude fat content were significantly influenced by N concentration and temperature, respectively, reaching 38.18 ± 0.08 % and 5.23 ± 0.04 %. Thirteen types of previously unreported trace fatty acids were identified, and the n-7 unsaturated fatty acid content increased with cultivation time progressed. Our results highlight the advantages of suspension culture, the suspension culture will contribute to the development of the macroalgae industry by encouraging the development of new breeding spaces centered around land-based aquaculture facilities and offering a mode for using airlift photobioreactors to produce safe food.