Abstract
Macroalgae are potentially excellent sources of bioactive secondary metabolites useful for the development of new functional ingredients. This study was conducted to determine the antimicrobial efficacy of the hot water crude extracts (HWCEs) of three species of local Thai green macroalgae Ulva intestinalis (Ui), U. rigida (Ur), and Caulopa lentillifera (Cl) and a commercial ulvan from U. armoricana (Ua). Chemical analysis indicated that the HWCE of Ur showed the highest sulfate content (13.9% ± 0.4%), while that of Ua contained the highest uronic acid and carbohydrate contents (41.47% ± 4.98% and 64.03% ± 2.75%, respectively), which were higher than those of Ur (32.75% ± 1.53% and 51.02% ± 3.72%). Structural analysis of these extracts by Fourier-transform infrared (FTIR) spectroscopy revealed that these HWCEs are complex with a signal at 1250 cm−1 corresponding to S=O stretching vibrations, while the signals at 850 cm−1 were attributed to the C–O–S bending vibration of the sulfate ester in the axial position. These HWCEs showed the growth suppression against some pathogenic Vibrio spp. Interestingly, the HWCEs from Ui at concentrations of 5 and 10 mg/mL completely inhibited white spot syndrome virus (WSSV) in shrimp injected with HWCE–WSSV preincubated solutions. This inhibitory effect was further confirmed by the reduction in viral loads and histopathology of surviving and moribund shrimp.
Highlights
The Pacific white shrimp (Litopenaeus vannamei) is a dominant crustacean in coastal aquaculture around the world and an important source of export earnings for developing countries in Asia andLatin America
The uronic acid content showed the maximal value in U. armoricana (Ua) at 41.47% ± 4.89%, which was significantly higher than that of U. rigida (Ur), U. intestinalis (Ui), and Caulopa lentillifera (Cl) with values of 32.76% ± 1.53%, 29.58% ± 1.66%, and 9.22% ± 0.56%, respectively (p < 0.05)
The present study demonstrated that hot water extraction is an effective method for sulfate polysaccharide extraction, as indicated by chemical and structural analyses of crude polysaccharides from three species of green algae compared with commercial purified ulvan
Summary
The Pacific white shrimp (Litopenaeus vannamei) is a dominant crustacean in coastal aquaculture around the world and an important source of export earnings for developing countries in Asia and. The worldwide marine shrimp aquaculture industry experienced rapid changes over the past few decades. While the global production of captured shrimp was fairly stable in recent years, that of cultured Pacific white shrimp expanded rapidly, from approximately 3,238,000 tons in 2012 to approximately 4,156,000 tons in 2016. Disease outbreaks and climate change are an ongoing challenge for some large Asian shrimp aquaculture producers, in Thailand and China [1]. The most important causative agents of shrimp diseases are currently pathogenic bacteria and viruses [2]. White spot syndrome virus (WSSV), which belongs to the family Nimaviridae, genus
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