Production of Ulva fasciata biomass through optimization of culture condition for viable tank-based edible seaweed farming

The present study focuses on the production of Ulva fasciata biomass by optimizing the culture conditions like nitrogen concentration, media usage, stocking density, and cultivation trail in outdoor cultivation. Overall, six types of experimental media, viz., N:P, NL:P, NL2:P, 0N:P, 2N:P, and 3N:P, along with control (without media) were used, and sodium nitrate was used as a nitrogen source. The experiment was conducted by using 30 PSU salinity seawater in 500-mL round-bottom conical flasks, and the duration of the experiment was for 15 days. During the experiment, every 5-day interval, the algal sample was collected, and DGR and length were measured to assess the growth of algae. The highest average DGR (13.79% day⁻¹) was found in the 3N:P combination (P < 0.001) with higher length (4.1 ± 0.3 cm) which was 4.85-folds higher than the initial length. For media usage and IPD optimization, the highest DGR was found in 100% of modified MP1 (2.87 ± 0.12% day⁻¹) and 1.0 g/5L IPD (8.04 ± 0.07% day⁻¹) than the other tested combinations. The outdoor tank cultivation (500 L) of U. fasciata exhibited higher growth rate (5.10 ± 0.19% day⁻¹), and higher length (3.8 ± 0.2 cm) was found on the 10th day. In 3N:P-treated U. fasciata, lipid (2.86 ± 0.08% DW) and carbohydrate (12.35 ± 0.29% DW) levels were high, while protein (2.79 ± 0.09% DW) levels were high in MP1 media fed U. fasciata. These results have revealed that the modified nitrogen-treated U. fasciata seedlings can grow in outdoor tanks without media and can also accumulate higher carbohydrate and lipid (with a high growth rate) than the wild plant as well as the conventional media (MP1) grown plants. Further research is required towards scaling up production for commercial purposes.