Optimization of ultrasound-assisted extraction of bioactive compounds and biopolymers from Ulva spp. using response surface methodology

Abstract Sea lettuce ( Ulva spp.), widely known for their fast growth and accumulation in coastal regions, represent an abundant and sustainable source for biomaterials. Their biomass, which often contributes to "green tides", holds great potential for various applications, including bioactive compound extraction. This study focused on optimizing the extraction of total phenolic compounds and ulvan from Ulva spp., leveraging both the promising potential of the algae and the efficiency of ultrasound-assisted extraction (UAE) as a sustainable method. Using response surface methodology (RSM), the optimal conditions were identified as 100% equipment amplitude (1300 W) and an unmodified pH of 5.7. These parameters led to the extraction of 0.253 ± 0.006 g GAE (100 g DW) −1 of total phenolic compounds and a 9.29 ± 0.47% yield of ulvan. The extracted ulvan exhibited remarkable structural properties, including a high molecular weight (≥ 800 kDa) and intermediate viscosity (~ 800 Pa s), alongside a stable antioxidant capacity. Fourier-transform infrared (FT-IR) analysis confirmed the ulvan's chemical consistency, while in vitro assays demonstrated strong cytocompatibility and immunomodulatory activity, reinforcing its potential for biomedical and food packaging applications.