Evaluation of cultivation potential and carrageenan properties of Hypnea sp. from Panay Island, Philippines

Abstract

<i>Hypnea</i> is a cosmopolitan genus of red seaweeds and an important source of carrageenan worldwide. However, <i>Hypnea</i> species remain largely unutilized in seaweed aquaculture in the Philippines. This study aimed to evaluate the growth performance and carrageenan properties of an indigenous, unexploited <i>Hypnea</i> sp. collected from Panay Island and to compare them with those of the commercially cultivated <i>Kappaphycus striatus</i>. In a field cultivation experiment, <i>Hypnea</i> sp. showed significantly higher biomass (145.1 ± 53.7 g) than <i>K. striatus</i> (92.9 ± 10.3 g) up to day 28 (<i>p</i> &lt; 0.001), while no significant difference was observed at days 36 and 43. The final yields were 181.0 ± 68.4 g for <i>Hypnea</i> sp. and 191.1 ± 33.0 g for <i>K. striatus</i> (<i>p</i> &gt; 0.05). Semi-refined carrageenan extracted from the cultured <i>Hypnea</i> sp. exhibited gel-forming capacity, suggesting the presence of κ-carrageenan. However, both the viscosity and gel strength of <i>Hypnea</i> sp. (9.52 ± 3.53 cP; 148 ± 41.6 g cm⁻²) were significantly lower in <i>K. striatus</i> (70.9 ± 49.4 cP; 456 ± 201 g cm⁻²) (<i>p</i> &lt; 0.001), indicating that <i>Hypnea</i> sp. possesses distinct carrageenan properties from conventional commercial seaweed. Although further development of carrageenan-based products tailored to its unique properties will be required for commercial utilization, these findings highlight the potential of <i>Hypnea</i> sp. as a candidate seaweed for aquaculture in the Philippines.