Evaluating the Prebiotic Properties of Agar Oligosaccharides Obtained from the Red Alga Gracilaria fisheri via Enzymatic Hydrolysis.

Currently, the demand in the food market for oligosaccharides with biological activities is rapidly increasing. In this study, agar polysaccharides from Gracilaria fisheri were treated with ß-agarases and hydrolyzed to agar oligosaccharides (AOSs). High-performance anion-exchange chromatography/pulsed amperometric detection (HPAEC-PAD), Fourier-transform infrared spectroscopy (FT-IR), and gel permeation chromatography (GPC), were employed to analyze the chemical characteristics of AOSs. The FT-IR spectra revealed that the enzymatic hydrolysis had no effect on specific functional groups in the AOS molecule. To investigate the prebiotic and pathogen inhibitory effects of AOSs, the influence of AOSs on the growth of three probiotic and two pathogenic bacteria was examined. The gastrointestinal tolerance of probiotics in the presence of AOSs was also investigated. AOSs enhanced the growth of Lactobacillus plantarum by 254%, and inhibited the growth of Bacillus cereus by 32.80%, and Escherichia coli by 58.94%. The highest survival rates of L. plantarum and L. acidophilus were maintained by AOSs in the presence of α-amylase and HCl under simulated gastrointestinal conditions. This study demonstrates that AOSs from G. fisheri exhibit potential as a prebiotic additive in foods.

Sulfated Galactans from Agarophytes: Review of Extraction Methods, Structural Features, and Biological Activities.

Agarophytes are important seaweeds of the Rhodophyta type, which have been highly exploited for industrial use as sources of a widely consumed polysaccharide of agar. In addition to that, sulfated galactans (SGs) from agarophytes, which consist of various functional sulfate groups, have attracted the attention of scientists in current studies. SGs possess various biological activities, such as anti-tumor, anticoagulant, anti-inflammatory, antioxidant, anti-obesity, anti-diabetic, anti-microbial, anti-diarrhea, and gut microbiota regulation properties. Meanwhile, the taxonomy, ecological factors, i.e., environmental factors, and harvest period, as well as preparation methods, i.e., the pretreatment, extraction, and purification conditions, have been found to influence the chemical compositions and fine structures of SGs, which have, further, been shown to have an impact on their biological activities. However, the gaps in the knowledge of the properties of SGs due to the above complex factors have hindered their industrial application. The aim of this paper is to collect and systematically review the scientific evidence about SGs and, thus, to pave the way for broader and otherwise valuable industrial applications of agarophytes for human enterprise. In the future, this harvested biomass could be sustainably used not only as a source of agar production but also as natural materials in functional food and pharmaceutical industries.

Inhibitory Effects of Caulerpa racemosa, Ulva intestinalis, and Lobophora challengeriae on Tyrosinase Activity and α-MSH-Induced Melanogenesis in B16F10 Melanoma Cells.

Melanogenesis involves a synthesis of melanin pigment and is regulated by tyrosinase. The addition of whitening agents with tyrosinase-inhibiting properties in cosmetics is becoming increasingly important. In this study, the ethanolic extracts from twelve seaweeds were assessed for tyrosinase-inhibiting activity using mushroom tyrosinase and melanin synthesis in B16F10 melanoma cells. The highest mushroom tyrosinase inhibition (IC50) was observed with Lobophora challengeriae (0.15 ± 0.01 mg mL-1); treatment was more effective than kojic acid (IC50 = 0.35 ± 0.05 mg mL-1), a well-known tyrosinase inhibitor. Three seaweeds, Caulerpa racemosa, Ulva intestinalis, and L. challengeriae, were further investigated for their ability to reduce melanogenesis in B16F10 cells. The ethanolic extracts of C. racemosa, U. intestinalis, and L. challengeriae showed inhibitory effects by reducing melanin and intracellular tyrosinase levels in B16F10 cells treated with α-melanocyte stimulating hormone in a dose-dependent manner. C. racemosa (33.71%) and L. challengeriae (36.14%) at 25 µg mL-1 reduced melanin production comparable to that of kojic acid (36.18%). L. challengeriae showed a stronger inhibition of intracellular tyrosinase (decreased from 165.23% to 46.30%) than kojic acid (to 72.50%). Thus, ethanolic extracts from C. racemosa, U. intestinalis, and L. challengeriae can be good sources of natural tyrosinase inhibitors and therapeutic or cosmetic agents in the future.

Ultrasonic-Assisted Extraction and Antioxidant Potential of Valuable Protein from Ulva rigida Macroalgae.

Ulva green macroalgae or sea lettuce are rich sources of protein with nutritional benefits that promote health as a future plant-based functional ingredient in the food industry. Alkaline pretreatment improved ultrasonic-assisted protein extraction from Ulva rigida biomass. Parameters affecting ultrasonic-assisted extraction of protein were type of solvent, biomass-solvent ratio, biomass preparation and extraction cycle. In vitro digestibility was evaluated from oven- and freeze-dried biomass. Results showed highest concentration and extraction yield of protein from U. rigida using alkaline rather than acid and distilled water. A high biomass-solvent ratio at 1:10 or 0.1 g mL-1 increased protein extraction. Higher alkaline concentration increased protein extraction. Highest protein extractability was 8.5% dry matter from freeze-dried U. rigida biomass, with highest protein extraction and antioxidant activity from extraction of U. rigida macroalgae at high alkaline concentrations. U. rigida macroalgae oven-dried biomass presented suitable human digestibility. Efficient pretreatment of U. rigida maximized protein hydrolysate and bioactive peptide production for wide-ranging applications.

Chemical composition of a hot water crude extract (HWCE) from Ulva intestinalis and its potential effects on growth performance, immune responses, and resistance to white spot syndrome virus and yellowhead virus in Pacific white shrimp (Litopenaeus vannamei).

In the present study, a hot water crude extract from Ulva intestinalis (Ui-HWCE) was used as a dietary supplement, and the effects on growth, immune responses, and resistance against white spot syndrome virus (WSSV) and yellowhead virus (YHV) infection in Pacific white shrimp (Litopenaeus vannamei) were investigated. Chemical analyses of Ui-HWCE revealed 13.75 ± 0.41% sulfate, 37.86 ± 5.96% uronic acid, and 46.63 ± 5.16% carbohydrate contents. The monosaccharide content of Ui-HWCE contained glucose (6.81 ± 0.94%), xylose (4.15 ± 0.11%), and rhamnose (25.84 ± 0.80%). Functional group analysis of Ui-HWCE by Fourier transform infrared (FTIR) spectroscopy revealed a typical infrared spectrum of ulvan similar to the infrared spectrum of commercially purified ulvan from Ulva armoricana (77.86 ± 2.19% similarity). Ui-HWCE was added to shrimp diets via top-dressing at 0, 1, 5, and 10 g/kg diet. After 28 days, Ui-HWCE supplementation at 5 g/kg diet efficiently improved shrimp growth performance, as indicated by weight gain, average daily growth, specific growth rates, and villus height determined by observing gut morphology. Additionally, Ui-HWCE feed supplementation at 5 g/kg diet significantly increased immune responses against a pathogenic bacterium (Vibrio parahaemolyticus AHPND stain), including phagocytic activity and clearance efficiency. Furthermore, Ui-HWCE feed supplementation upregulated the expression of several immune-related genes in the hemocytes and gills. Ui-HWCE supplementation at 1 and 5 g/kg resulted in effective anti-YHV but not anti-WSSV activity, which significantly decreased the mortality rate and YHV burden in surviving shrimp. It was concluded that Ui-HWCE supplied at 5 g/kg diet exhibits growth-promoting, immune-stimulatory, and antiviral activity that could protect L. vannamei against YHV infection.

Antibacterial and Antiviral Activities of Local Thai Green Macroalgae Crude Extracts in Pacific white Shrimp (Litopenaeus vannamei).

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.

Bioencapsulation efficacy of sulfated galactans in adult Artemia salina for enhancing immunity in shrimp Litopenaeus vannamei.

Live food organisms like Artemia have been used for delivery of different substances such as nutrients, probiotics and immune-stimulants to aquatic animals. Previously, we reported that sulfated galactans (SG) from the red seaweed Gracilaria fisheri (G. fisheri) increased immune activity in shrimp. In the present study we further investigated the capacity and efficiency of bioencapsulation of SG in adult Artemia for delivery to tissues and potentially boosting the expression of immune genes in post larvae shrimp. SG were labelled with FITC (FITC-SG) for in vivo tracking in shrimp. Bioencapsulation of adult Artemia with FITC-SG (0-100 µg mL-1) was performed and the fluorescence intensity was detected in the gut lumen after enrichment periods of 30 min, 1 h, 2 h, 6 h and 24 h. The results showed the Artemia took up SG over time in a concentration-dependent manner. Shrimp were fed with the bioencapsulated Artemia (FITC-SG, 20 µg mL-1) and the shrimp were evaluated under a stereo-fluorescent microscope. At 24 h after administration, FITC-SG was located in gills and hepatopancreas and also bound with haemocytes. With daily SG administration, the genes IMD, IKKß were up-regulated (after 1 day) while genes dicer and proPO-I were up-regulated later (after 7 days). Moreover, continued monitoring of shrimp fed for 3 consecutive days only with SG at the dose of 0.5 mg g-1 BW showed increases in the expression of IMD, IKKß genes on day 1 and which gradually declined to normal levels on day 14, while the expression of dicer and proPO-I was increased on day 3 and remained high on day 14. These results demonstrate that bioencapsulation of SG in adult Artemia successfully delivers SG to shrimp tissues, which then bind with haemocytes and subsequently activate immune genes, and potentially increase immunity in shrimp. In addition, the present study suggests that a 3-consecutive-day regimen of SG supplemented in Artemia (0.5 mg g-1 BW) may boost and sustain the enhanced immune functions in post larvae shrimp.

Immunostimulatory activity of sulfated galactans isolated from the red seaweed Gracilaria fisheri and development of resistance against white spot syndrome virus (WSSV) in shrimp.

Sulfated galactans (SG) were isolated from the red seaweed Gracilaria fisheri (G. fisheri). Chemical analysis revealed SG contains sulfate (12.7%) and total carbohydrate (42.2%) with an estimated molecular mass of 100 kDa. Structure analysis by NMR and FT-IR spectroscopy revealed that SG is a complex structure with a linear backbone of alternating 3-linked ß-D-galactopyranose and 4-linked 3,6-anhydrogalactose units with partial 6-O-methylate-ß-D-galactopyranose and with sulfation occurring on C4 of D-galactopyranose and C6 of L-galactopyranose units. SG treatment enhanced immune parameters including total haemocytes, phenoloxidase activity, superoxide anions and superoxide dismutase in shrimp Penaeus monodon. Shrimp fed with Artemia salina enriched with SG (100 and 200 µg ml(-1)) and inoculated with white spot syndrome virus (WSSV) showed a significantly lower mortality rate and lower viral VP 28 amplification and expression than control. The results suggest that SG from G. fisheri exhibits immune stimulatory and antiviral activities that could protect P. monodon from WSSV infection.