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

Evaluating the Prebiotic Properties of Agar Oligosaccharides Obtained from the Red Alga <i>Gracilaria fisheri</i> 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 β-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

<span style="font-size:15.0pt;mso-bidi-font-family:"Times New Roman";mso-bidi-font-weight: bold" lang="EN-GB">Screening, phenotypic and genotypic identification of β-carotene producing strains of <i style="mso-bidi-font-style:normal">Dunaliella</i> <i style="mso-bidi-font-style:normal">salina</i> from Thailand </span>

2198-2216<i style="mso-bidi-font-style: normal">Dunaliella salina is a salt-loving microalga that accumulates high amounts of β-carotene when cultivated under unfavorable conditions. In this study we aimed to screen <span style="mso-bidi-font-weight:bold; mso-bidi-font-style:italic">β-carotene producing strains of D.salina <span style="mso-bidi-font-style: italic">from salt soil samples collected from 19 provinces in the northeastern part of Thailand. For preliminary screening 70 pure isolated strains were screened by using 18S rDNA conserved primers (MA1&MA2), only 15 isolates produced a band (~2100 bp) as that of <i style="mso-bidi-font-style: normal">D.salina.  For the o<span style="mso-bidi-font-style: italic">bservation of β-carotene production, these 15 isolates were grown on agar plate containing modified Ramaraj medium with 1.0 M NaCl under continuous illumination.  After a month only 3 isolates completely turned red. However, by using the banding pattern produced by 18S rDNA primers, the 15 isolates could not be differentiated between the β-carotene and non β-carotene producing strains. Comparing the above results we found that the <span style="mso-bidi-font-style: italic">observation of β-carotene production on agar plate is more easy and suitable method than molecular technique to screen β-carotene producing strains. Morphological characteristics of the 3 screened Thai isolates clearly delineated that it belongs to the genus Dunaliella. ITS-RFLP banding pattern, 18S rDNA, ITS and RuBisCo large subunit (rbcL) sequences were used to confirm at the species level. These results indicated that these 3 isolates are D.salina and were named <i style="mso-bidi-font-style: normal">D.salina strain KU07, D.salina strain KU11 and D.salina strain KU13. Under non-stress conditions these 3 strains had an ability to accumulate β-carotene up to 5.61±0.25, 7.58±0.19 and 6.73±0.32 pg/cell, respectively. </span

Inhibitory Effects of <i>Caulerpa racemosa</i>, <i>Ulva intestinalis</i>, and <i>Lobophora challengeriae</i> 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 <i>Ulva rigida</i> 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