Aquaculture of green seaweed Ulva intestinalis in brackish water and its potential as food and feed ingredient

Abstract

The global population growth predicts soaring demands on food production. Ecological constraints necessitate a thorough examination of alternative protein sources to animal derived products. Recently, seaweeds have been gaining attention as a sustainable source of nutrition that could contribute to the rapidly developing global food production demands. However, seaweeds react differently to environmental stimuli such as salinity and temperature. The purpose of this study was to study how temperature and nutrient density in low salinity affect the growth, protein content and amino acid profile of a green seaweed, Ulva intestinalis. Additionally, cultivation potential in the low salinity of the Baltic sea was evaluated. Samples of U. intestinalis were cultivated in orthogonal combinations of two temperatures and two nutrient levels for four weeks, 10 °C and 25 °C, F/2 (high) and F/20 (low) Medium, respectively. Ground and freeze-dried samples were quantified for total chlorophyll and protein content using absorbance in dimethylformamide and the Lowry Protein Assay, respectively. The amino acid profile was determined using HPLC-FLD and a Zorbax Eclipse AAA column to detect the derivatized amino acids. Samples grown in 10 °C maintained a relatively consistent growth rate of 38 % and 26 % (w.b.) on average, respectively, while samples grown in 25 °C plateaued in biomass growth between the 2nd and 3rd week. The chlorophyll a, chlorophyll b, and carotenoid contents of both F/2 25 °C and F/2 10 °C samples were about 2.2, 8.3, and 2.0-fold compared to both F/20 25 °C and F/20 10 °C samples, respectively. Temperature significantly affected the total protein content as well as serine, histidine, and lysine concentrations, while nutrient level affected significantly only lysine.