Edible-algae base composite film containing gelatin for food packaging from macroalgae, Gracilaroid (Gracilaria fisheri)

BACKGROUND

Conventional petroleum-based packaging films cause severe environmental problems. In this work bio-edible film as a safe to replace petroleum-based polymers was introduced. A food application for edible sachets and a composite edible film (EF) from marine algae, Gracilaria fisheri (GF) extract were proposed.

RESULTS

Carbohydrates were the most prevalent component in fresh GF fronds. Under neutral conditions at 90 °C for 40 min, the extract's structure was determined by FTIR to be a carrageenan-like polysaccharide. Glycerol was the best plasticizer for EF formation since it had the highest tensile strength (TS). The integration of gelatin into the algal composite film with gelatin (CFG) was validated by significant. The best casting temperatures for 2 h were 70 and 100 °C among the four tested temperatures (25, 60, 70, and 100 °C). Temperatures did not result in significant (p ≤ 0.05) differences in any character (color values, TS, water vapor permeability, oxygen transmission, thickness, and water activity), except elongation at break. Visually, the CFG had a slightly yellow appearance. The best-to-worst order of film stability in the three tested solvents was oil, distilled water (DW), and ethanol. Its stability in ethanol (0-100%), temperature of DW (30-100 °C), and pH (3-7 in DW) demonstrated inverse variations with the concentration or different conditions, except for pH 8-10 in DW. All treatments were significantly (p ≤ 0.05) different.

CONCLUSION

The novel material made from polysaccharides from algae, G. fisheri, was used to improve EF. The edible sachet application was plausible from the EF. This article is protected by copyright. All rights reserved.

Characterization and immunomodulatory activity of sulfated galactan from the red seaweed Gracilaria fisheri

Polysaccharides from the red seaweed Gracilaria fisheri possess many functions, which include antioxidant, antiviral, and antibacterial activities. However, detailed data on their immunomodulatory activities are scarce. Here, we isolated sulfated galactans (SG) from G. fisheri. We found that the predominant SG from G. fisheri, termed SG-1, had an estimated molecular mass of 100 kDa and activated murine J774A.1 macrophages via the dectin-1 signaling pathway. Furthermore, we observed enhancement of nitric oxide (NO) secretion, increased expression of inducible nitric oxide synthase (iNOS) mRNA, and increased mRNA levels of pro-inflammatory cytokines such as tumor necrosis factor-α (TNF-α) and interleukins IL-1β and IL-6 by SG-1 in macrophages. Moreover, there was higher expression of intercellular adhesion molecule 1 (ICAM-1) and co-stimulatory molecules (B7-1 and B7-2) mRNA. Treatment with G. fisheri SG-1 at 50 μg/mL generally achieved or exceeded the pro-inflammatory activities of 100 ng/mL lipopolysaccharide. Our study demonstrates immune-stimulatory activities of G. fisheri SG that may be of value for immune-potentiating treatment in humans or livestock.

Development of Optimal Digesting Conditions for Microplastic Analysis in Dried Seaweed Gracilaria fisheri

Currently, research on the accumulation of microplastics (MPs) in the marine food web is being highlighted. An accurate and reliable digestion method to extract and isolate MPs from complex food matrices has seldom been validated. This study aimed to compare the efficacy of MP isolation among enzymatic-, oxidative-, and the combination of two digestion methods on red seaweed, Gracilaria fisheri. The dried seaweed sample was digested using three different methods under various conditions using enzymes (cellulase and protease), 30% H₂O₂, and a combination of enzymes and 30% H₂O₂. The method possessing the best digestion efficiency and polymer recovery rate of MPs was selected, and its effect on spiked plastic polymer integrity was analyzed by Raman spectroscopy. As a result, the enzymatic method rendered moderate digestion efficiency (59.3–63.7%) and high polymer recovery rate (94.7–98.9%). The oxidative method using 30% H₂O₂ showed high digestion efficiency (93.0–96.3%) and high polymer recovery rate (>98%). The combination method was the most effective method in terms of digestion efficiency, polymer recovery rate, and expenditure of digestion time. The method also showed no chemical changes in the spiked plastic polymers (PE, PP, PS, PVC, and PET) after the digestion process. All the spiked plastic polymers were identifiable using Raman spectroscopy.

Purification and Evaluation of N-benzyl Cinnamamide from Red Seaweed Gracilaria fisheri as an Inhibitor of Vibrio harveyi AI-2 Quorum Sensing

Previously, we reported that the ethanol extract from red seaweed Gracilaria fisheri effectively decreased biofilm formation of Vibrio harveyi. In this study, the anti-biofilm active compounds in the ethanol extract were isolated and their structures identified. The anti-biofilm fractionation assay for minimum inhibitory concentration (MIC) produced two fractions which possessed maximal inhibitory activities toward the biofilm formation of V. harveyi strains 1114 and BAA 1116. Following chromatographic separation of the bioactive fractions, two pure compounds were isolated, and their structures were elucidated using FTIR, NMR, and HR-TOF-MS. The compounds were N-benzyl cinnamamide and α-resorcylic acid. The in vitro activity assay demonstrated that both compounds inhibited the biofilm formation of V. harveyi and possessed the anti-quorum sensing activity by interfering with the bioluminescence of the bacteria. However, the N-benzyl cinnamamide was more potent than α-resorcylic acid with a 10-fold lesser MIC. The present study reveals the beneficial property of the N-benzyl cinnamamide from the ethanol extract as a lead anti-microbial drug against V. harveyi.

Sulfated galactans from the red seaweed Gracilaria fisheri exerts anti-migration effect on cholangiocarcinoma cells

BACKGROUND

Seaweeds have a long history of use in Asian countries as functional foods, medicinal herbs, and the treatment of cancer. Polysaccharides from various seaweeds have shown anti-tumor activity. Cholangiocarcinoma (CCA), often with metastatic disease, is highly prevalent in Thailand as a consequence of liver fluke infection. Recently, we extracted sulfated galactans (SG) from Gracilaria fisheri (G. fisheri), a south east Asian seaweed, and found it exhibited anti-proliferation effect on CCA cells.

PURPOSE

In the present study, we evaluated the anti-migration activity of SG on CCA cells and its underlined mechanism.

METHODS

CCA cells were treated with SG alone or drugs targeting to epidermal growth factor (EGF) receptor (EGFR) or pretreated with SG prior to incubation with EGF. Anti-migration activity was determined using a scratch wound-healing assay and zymography. Immunofluorescence staining and western blotting were used to investigate EGFR signaling mediators.

RESULTS

Under basal condition, SG reduced the migration rate of CCA, which was correlated with a decrease in the active-form of matrix metalloproteinases-9. SG decreased expression of phosphorylated focal adhesion kinase (FAK), but increased expression of E-cadherin to promote cells stasis. Moreover, phosphorylation of EGFR and extracellular signal-regulated kinases (ERK), known to stimulate growth of cancer cells, was blocked in a comparable way to EGFR inhibitors Cetuximab and Erlotinib. Pretreatment cells with SG attenuated EGF induced phosphorylation of EGFR, ERK and FAK.

CONCLUSION

This study reveals that SG from G. fisheri retards migration of CCA cells, and its mechanism of inhibition is mediated, to some extent, by inhibitory effects on MAPK/ERK signal transduction pathway. Our findings suggest that there may be a therapeutic potential of SG in CCA treatment.

Sulfated galactans from Gracilaria fisheri bind to shrimp haemocyte membrane proteins and stimulate the expression of immune genes

Previous studies demonstrated that sulfated galactans (SG) from Gracilaria fisheri (G. fisheri) exhibit immunostimulant activity in shrimp. The present study was conducted to test the hypothesis that SG stimulates signaling molecules of the immune response of shrimp by binding to receptors on the host cell membrane. Accordingly, we evaluated the ability of SG to bind to shrimp haemocytes and showed that SG bound to the shrimp haemocyte membrane (SHM), potentially to specific receptors. Furthermore, this binding was associated with an activation of immune response genes of shrimp. Data from confocal laser scanning micrographs revealed that FITC-labeled SG bound to haemocytes. Far western blot analysis demonstrated that SHM peptides, with molecular sizes of 13, 14, 15, 17, and 25 kDa, were associated with SG. Peptide sequence analysis of the isolated bands using LC-MS/MS and NCBI blast search revealed the identity of the 13, 14, and 17 kDa peptides as lipopolysaccharide and β-1,3-glucan binding protein (LGBP). SG induced the expression of immune related genes and downstream signaling mediators of LGBP including IMD, IKKs, NF-κB, antimicrobial peptides (crustin and PEN-4), the antiviral immunity (dicer), and proPO system (proPO-I and proPO-II). A LGBP neutralizing assay with anti-LGBP antibody indicated a decrease in SG-induced expression of LGBP downstream signaling mediators and the immune related genes. In conclusion, this study demonstrated that the SG-stimulated immune activity in haemocytes is mediated, in part, through the LGBP, and IMD-NF-κB pathway.

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 β-D-galactopyranose and 4-linked 3,6-anhydrogalactose units with partial 6-O-methylate-β-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.