Efficient Extraction of Biologically Active and Technofunctional Sulfated Polysaccharides From Green Seaweed Ulva rigida Using Enzyme‐Assisted Method

The current study employed the enzyme‐assisted extraction for the bioconversion of Ulva rigida and isolating the ulvan polysaccharide. The extracted ulvan was characterized using Fourier transform infrared spectroscopy, x‐ray diffraction, electrospray ionization‐mass spectrometry, and differential scanning calorimetry analysis. The antioxidant activity (scavenging of DPPH free radical and reducing power assays), antibacterial activity (against four food pathogenic bacteria), prebiotic activity, water‐ and oil‐holding capacities, and emulsifying and foaming properties of the isolated ulvan were investigated. The ulvan yield from U. rigida by the enzyme method was 37.8%. The extracted ulvan possesses 92.64% DPPH scavenging and 0.2515 Abs, reducing power activities at a concentration of 4 mg/mL. Antibacterial studies revealed that the isolated ulvan exerted antibacterial activity against Escherichia coli and Listeria monocytogenes with 5‐ and 4‐mm semidiameter inhibition zones at 10 mg/mL concentrations, respectively. However, it was not active against Staphylococcus aureus and Salmonella enterica . The growth of Bifidobacterium bifidum , Lactobacillus acidophilus , and Lactobacillus plantarum bacteria was increased in the presence of the extracted ulvan, which indicates its prebiotic activity. The water‐holding capacity of the extracted ulvan (6.18 g water/g sample) was higher than its oil‐holding capacity (0.5 g oil/g sample). The results also demonstrated that the extracted ulvan could emulsify the corn, sunflower, and canola oils. The foaming capacity and stability of the extracted ulvan were 14.08% and 4.30%, respectively. These results suggested that the enzyme method recovered ulvan from U. rigida with different bioactivities and technofunctional properties, making it suitable for application in various food and cosmetic products as a nutraceutical and natural preservative.