Impact of growth conditions on the nitrogen, protein, colour and amino acid profiles of the cultured macroalga, Palmaria palmata

The impact of growth conditions on the nitrogen, protein, colour and amino acid profiles of Palmaria palmata (from 2 locations) were investigated. Laboratory cultures of P. palmata were grown over a period of 18 days with and without nutrient addition, i.e., with culture medium (F/2) and urea (0.05 or 0.10 g L⁻¹). The total nitrogen (TN) content of cultured P. palmata originating from longlines harvested from Cork increased with the addition of culture medium (F/2) and urea (0.05 g L⁻¹) in comparison to the initial sample (4.15 ± 0.05 vs 1.73 ± 0.03%) while biomass from Galway increased with addition of culture medium (F/2) and urea (0.10 g L⁻¹) in comparison to the initial sample (3.72 ± 0.05 vs 2.43 ± 0.06%). The protein nitrogen (PN) and non-protein nitrogen (NPN) of cultured P. palmata originating from Galway also increased when grown with the addition of nutrients. Nutrient enrichment during growth influenced the colour characteristics (lightness L*, redness a*, yellowness b* and colour difference ΔE) and the electrophoretic protein profile. Correlations between TN and ΔE (r = 0.945) for Cork originated sample, PN and ΔE (r =-0.944) and NPN and ΔE (r = 0.734) for Galway originated sample were observed. In-gel digestion followed by UPLC-MS/MS demonstrated that RuBiSCo, phycoerythrin and allophycocyanin expression in P. palmata was enhanced with nutrient addition. Amino acid profile and score analysis showed variation as a function of nutrient addition. Overall, nutrient inclusion in the growth medium provides a strategy for the enhanced production of high-quality protein by P. palmata.