Seasonal variations in growth and phytochemical compounds of cultivated red alga, Hypnea flagelliformis, in southern coastlines of Iran

Global utilization of seaweeds for food, chemicals, pharmaceuticals, and production of polysaccharide is increasing and seaweeds are becoming the most important cultivated marine organisms. This study assessed the cultivation potential of the red alga, Hypnea flagelliformis , along the southern coastlines of Iran using monoline plastic rope method, with regard to several environmental parameters of seawater over a year (November 2017 to October 2018). Correlations between relative growth rate (RGR) and environmental parameters were investigated using Pearson correlation analysis. Biochemical composition contents (moisture, ash, protein, and lipid) of the cultivated samples were measured during the experiment. Yield and structural properties of the extracted carrageenan using aqueous and alkali-treated extraction of the samples were investigated using Fourier transform infrared (FT-IR) spectroscopy. This study showed that this species can grow only in 6 months of the year (November to April) in outdoor conditions. The highest relative growth rate (9 ± 0.4% day −1 ) was obtained in December. Salinity and temperature had significant impacts on the growth of H. flagelliformis . The biochemical composition content range for moisture (86.76-91.76% fw), ash (30-39% dw), total protein (1.40-3.03% dw), and lipid (1.08-3.15% dw) varied during the experiment. The yield of alkali-treated carrageenan (mean 34.5 ± 2.5% dw) was higher than aqueous method (mean 20.7 ± 1.3% dw). FT-IR analysis indicated that the extracted hydrocolloids are mainly from κ-carrageenan type. The findings demonstrate that H. flagelliformis has good potential for cultivation and as a carrageenan source.