Characterization, ultrafiltration, depolymerization and gel formulation of ulvans extracted via a novel ultrasound-enzyme assisted method.

Sea lettuce, or Ulva spp., dominates global algal biomass and significantly contributes to "green tides.", representing a sustainable source for biomaterials. This study explores an innovative ultrasound-enzyme assisted extraction method with the novel Cellic® CTEC3 enzyme cocktail, applied for the first time in Ulva spp. succesfully enhancing ulvan release and extraction efficiency. Various processing methods, including ultrafiltration and dialysis, were employed to achieve higher ulvan purity. Dialyzation of ulvan resulted in a more purified product with a carbohydrate content up to 55.34 %, a sulfate content up to 21 %, and no glucose contamination. Liquid extracts were fractionated through ultrafiltration, with a 3 kDa MWCO yielding 93.51 % ulvan precipitate, representing 50.28 % of the total extractable ulvan. Sequential ultrafiltration concentrated ulvans but only partially modified their molecular weight distribution. Depolymerization using microwave and H2O2 shifted ulvans towards lower molecular weights, reducing high molecular weight residue. HPSEC confirmed pH-dependent aggregation behavior, with all isolated ulvans having molecular weights above 786 kDa. Hydrolysis methods were compared, with 2-hour 1 M TFA hydrolysis at 121 °C providing the best monosaccharide profile of ulvan. FTIR and NMR analyses showed preservation of sulfation. Rheology indicated biopolymeric behavior and stable gel formation. Ulvans demonstrated nutraceutical potential, being suitable for a low Na+ and high K+ diet, with a Na+:K+ ratio as low as 0.14, and were rich in Mg2+.

Healing Potential of the Marine Polysaccharides Carrageenan and Ulvan on Second-Degree Burns.

The treatment of second-degree burn wounds presents a significant clinical challenge, often characterized by prolonged healing times and risk of complications. In this study, the wound healing potential of bioactive marine sulfated polysaccharides ulvan and carrageenan formulated in gels at concentrations of 1.5%, 5.0%, and 10% w/w was evaluated. Hairless female SKH-hr2 mice (n = 7 per treatment) with burn-inflamed skin were treated with the polysaccharide-based gels, and the therapeutic efficacy was assessed using a comprehensive array of evaluation methods, including a histopathological analysis, clinical observation, photo-documentation, an image analysis, an evaluation of biophysical skin parameters, and FT-IR spectroscopy. Our findings indicate that the 10% w/w carrageenan gel exhibited significant enhancement in wound healing, particularly in the early stages of the healing process. This was evidenced by the restoration of the α-helix structure of collagen and the configuration of glycosaminoglycans, as demonstrated by FT-IR absorption bands of the skin both in vivo and ex vivo. Furthermore, the 5% w/w ulvan gel also demonstrated notable efficacy in promoting wound healing, particularly in the later stages of the healing process. These results suggest that carrageenan and ulvan gels hold promise for improving the efficiency of wound healing in second-degree burn wounds. Our study contributes to the understanding of the therapeutic potential of marine polysaccharides and provides insights into their mechanism of action in promoting wound healing.

Sustainable Production of Ulva Oligosaccharides via Enzymatic Hydrolysis: A Review on Ulvan Lyase.

Ulvan is a water-soluble sulfated polysaccharide extracted from the green algae cell wall. Compared with polysaccharides, oligosaccharides have drawn increasing attention in various industries due to their enhanced biocompatibility and solubility. Ulvan lyase degrades polysaccharides into low molecular weight oligosaccharides through the ß-elimination mechanism. The elucidation of the structure, catalytic mechanism, and molecular modification of ulvan lyase will be helpful to obtain high value-added products from marine biomass resources, as well as reduce environmental pollution caused by the eutrophication of green algae. This review summarizes the structure and bioactivity of ulvan, the microbial origin of ulvan lyase, as well as its sequence, three-dimensional structure, and enzymatic mechanism. In addition, the molecular modification of ulvan lyase, prospects and challenges in the application of enzymatic methods to prepare oligosaccharides are also discussed. It provides information for the preparation of bioactive Ulva oligosaccharides through enzymatic hydrolysis, the technological bottlenecks, and possible solutions to address these issues within the enzymatic process.

Immunostimulating effects of ulvan type polysaccharide isolated from Korean Ulva pertusa in cyclophosphamide-induced immunosuppressed BALB/c mice.

This study aimed to determine the immunostimulatory activities of ulvan type polysaccharides isolated from Ulva pertusa. First, U. pertusa polysaccharide (UPP) mainly consists of rhamnose, glucuronic acid, iduronic acid, and xylose, which are typical ulvan type monosaccharides. UPP induced phosphorylation of the mitogen-activated protein kinase and nuclear factor-kappa B pathways in macrophages, subsequently triggering cytokine release and phagocytosis. The effects were closely associated with pattern recognition receptors such as dectin-1, mannose receptor, CD11b, CD14, and Toll-like receptors 2 and 4. Moreover, prophylactic administration of UPP was found to protect against body weight loss and lymphatic organ damage in cyclophosphamide-induced immunosuppressed mice. In addition, UPP demonstrated significant stimulatory effects on various immunocytes, such as T cells, B cells, macrophages, and natural killer cells derived from the spleen. These effects were closely related to the mitogen-activated protein kinase and nuclear factor-kappa B pathways, and significant secretion of immunostimulatory cytokines such as IL-6, -12, and TNF-α was noted in both blood and spleen samples. Impairment of the short-chain fatty acid balance in the cecum was prevented by UPP administration in a dose-dependent manner. Consequently, these results suggest that the UPP isolated from U. pertusa contributes to immune system activation.

Characterization of a novel sulfated-rhamnoglucuronan isolated from Korean seaweed Ulva pertusa and its efficacy for treatment of inflammatory bowel disease in mice.

This study aimed to isolate Ulva pertusa polysaccharide (UPP), which elicits anti-inflammatory bowel disease (IBD) effects, from the Korea seaweed U. pertusa and identify its structure. Firstly, UPP was isolated from U. pertusa using hydrothermal extraction and ethanol precipitation. UPP is a novel polysaccharide that exhibits unique structural features such as 3-sulfated rhamnose, glucuronic acid, iduronic acid, and 3-sulfated xylose, which are repeated in 1,4-glycosidic bonds. Prophylactic oral administration of UPP in mice with dextran sulfate sodium (DSS)-induced ulcerative colitis (UC) suppressed the levels of inflammatory cytokines and MAPK- and NF-κB-related factors in the serum and colon tissue. Tight junction (TJ)-related factors such as occludin, claudin-1, and mucin were effectively augmented by UPP in the colon tissue. In addition, UPP administration prevented the DSS treatment-led cecal short chain fatty acid imbalance, and this effect was most evident for propionic acid. In conclusion, UPP isolated from the Korean U. pertusa demonstrates potent anti-IBD activity. Characterization of this ulvan revealed its unique structure. Moreover, its efficacy may be associated with its anti-inflammatory effects and regulation of gut microbiota and TJ proteins. Thus, this study provides new insights into the biological effects of UPP in IBD.

Potentials of Ulva spp.-derived sulfated polysaccharides as gelling agents with promising therapeutic effects.

Ulvan, a sulfated polysaccharide extracted from Ulva spp., has garnered significant attention in the food and pharmaceutical industries due to its potential health benefits. These include immunomodulation, antiviral, anti-inflammatory, anti-hyperlipidemic, and anti-cancer effects. Nonetheless, practical applications in these fields remain limited due to an incomplete understanding of its gelation mechanisms. Additionally, the underlying mechanisms of its gelation have not been completely understood and thoroughly reviewed. The primary objective is to provide current insights into ulvan's gelling mechanisms and potential health impacts. This review also delves into the existing applications of ulvan polysaccharides. By unraveling these aspects, the information provided in this work is expected to deepen our understanding of ulvan's gelation mechanisms and its prospective role in enhancing health, holding promise for advancements in the fields of food science and disease prevention. This work's theoretical insights contribute significantly to a deeper understanding of these aspects, which holds paramount importance in unleashing the full potential of ulvan and elevating its scientific significance.

Biochemical characterisation of a PL24 ulvan lyase from seaweed-associated Vibrio sp. FNV38.

Ulvan is a green macroalgal cell wall polysaccharide that has tremendous potential for valorisation due to its unique composition of sulphated rhamnose, glucuronic acid, iduronic acid and xylose. Several potential applications such as production of biofuels, bioplastics and other value-added products necessitate the breakdown of the polysaccharide to oligomers or monomers. Research on ulvan saccharifying enzymes has been continually increasing over the last decade, with the increasing focus on valorisation of seaweed biomass for a biobased economy. Lyases are the first of several enzymes that are involved in saccharifying the polysaccharide and several ulvan lyases have been structurally and biochemically characterised to enable their effective use in the valorisation processes. This study investigates the whole genome of Vibrio sp. FNV38, an ulvan metabolising organism and biochemical characteristics of a PL24 ulvan lyase that it possesses. The genome of Vibrio sp. FNV38 has a diverse CAZy profile with several genes involved in the metabolism of ulvan, cellulose, agar, and alginate. The enzyme exhibits optimal activity at pH 8.5 in 100 mM Tris-HCl buffer and 30 °C. However, its thermal stability is poor with significant loss of activity after 2 h of incubation at temperatures above 25 °C. Breakdown product analysis reveals that the enzyme depolymerised the polysaccharide predominantly to disaccharides and tetrasaccharides. Supplementary Information: The online version contains supplementary material available at 10.1007/s10811-023-03136-3.

Biochemical Characterization of a Novel Thermostable Ulvan Lyase from Tamlana fucoidanivorans CW2-9.

Ulvan is a complex sulfated polysaccharide extracted from Ulva, and ulvan lyases can degrade ulvan through a ß-elimination mechanism to obtain oligosaccharides. In this study, a new ulvan lyase, EPL15085, which belongs to the polysaccharide lyase (PL) 28 family from Tamlana fucoidanivorans CW2-9, was characterized in detail. The optimal pH and salinity are 9.0 and 0.4 M NaCl, respectively. The Km and Vmax of recombinant EPL15085 toward ulvan are 0.80 mg·mL-1 and 11.22 µmol·min -1 mg-1·mL-1, respectively. Unexpectedly, it is very resistant to high temperatures. After treatment at 100 °C, EPL15085 maintained its ability to degrade ulvan. Molecular dynamics simulation analysis and site-directed mutagenesis analysis indicated that the strong rigidity of the disulfide bond between Cys74-Cys102 in the N-terminus is related to its thermostability. In addition, oligosaccharides with disaccharides and tetrasaccharides were the end products of EPL15085. Based on molecular docking and site-directed mutagenesis analysis, Tyr177 and Leu134 are considered to be the crucial residues for enzyme activity. In conclusion, our study identified a new PL28 family of ulvan lyases, EPL15085, with excellent heat resistance that can expand the database of ulvan lyases and provide the possibility to make full use of ulvan.

Ulvans are not equal - Linkage and substitution patterns in ulvan polysaccharides differ with Ulva morphology.

Ulva are hardy green seaweeds that contain the sulfated polysaccharide ulvan and grow in two distinct morphologies: foliose and tubular. The authors hypothesise that ulvan from tubular species are more structurally complex than ulvans from foliose species. Herein, using standardised methods, the glycosyl linkage positions and sulfate ester substitutions of constituent monosaccharides of ulvan isolated from foliose (U. lacinulata and U. stenophylloides) and tubular (U. prolifera and U. ralfsii) species of Ulva were investigated. Comparison of native ulvans with 80 and 100 °C desulfated counterparts indicated that 4-linked rhamnose is predominantly 3-O-sulfated in all four ulvans. Ulvans from the foliose species predominantly contained →3,4)-Rhap-(1→, →4)-GlcAp-(1→ and →4)-IdoAp-(1→, collectively accounting for 67 to 81 mol% of the total linkages. In contrast, these same linkages in ulvans from the tubular species only collectively accounted for 29 to 36 mol%. Instead, ulvan from tubular species contained a combination of →2,3,4)-Rhap-(1→, terminal Rhap-(1→, →4)-GlcAp-(1→, →4)-Xylp-(1→, and/or →4)-Galp-(1→ in high proportions; some of the latter three residues were also likely O-2 sulfated. The results presented here suggest that ulvan from foliose species are predominantly unbranched polysaccharides composed of repeat disaccharides while ulvans from tubular species contain a greater diversity of branch and sulfate substitution locations.

Characterization and Biological Activities of the Ulvan Polysaccharide-Rich Fraction Obtained from Ulva rigida and Ulva pseudorotundata and Their Potential for Pharmaceutical Application.

Seaweed from the genus Ulva (Ulvales, Chlorophyta) has a worldwide distribution and represents a potential biomass source for biotechnological applications. In the present study, we investigated the ulvan polysaccharide-rich fraction (UPRF) isolated from two Ulva species (U. rigida and U. pseudorotundata), naturally occurring on the Spanish Mediterranean coast. Chemical characterization of UPRFs was performed in order to explore the polysaccharides' composition. Biological assessments of UPRFs were compared by antioxidant activity and in vitro toxicity tests in the human cell lines: HCT-116 (colon cancer), G-361 (malignant melanoma), U-937 (leukemia), and HaCaT cells (immortalized keratinocytes). Chemical analysis revealed that both UPRFs presented rhamnose as the major relative sugar constituent, followed by glucose in U. rigida and xylose in U. pseudorotundata. Both also presented glucuronic acid, galactose, ribose, and mannose as the remaining monosaccharides. Similar antioxidant activity was obtained, where we observed increased activity in response to increased polysaccharide concentrations. Both UPRFs presented moderate toxicity against HCT-116 cell lines and a selectivity index ≥ 3, suggesting a good potential for use in pharmaceutical products.

Genome sequence of Vibrio sp. strain 10N, an ulvan-degrading bacterium isolated from coastal seawater collected at Ise Bay, Japan.

Genome sequence of an ulvan-degrading bacterium, Vibrio sp. strain 10N, is presented. The genome is 5,358,550 bp with a G + C content of 46.5%. A total of 4,712 coding sequences, including two novel ulvan lyase genes encoding a BNR4 and a glycoside hydrolase (GH88) motif, are known to be involved in the degradation of green algae.

Assessing the role of ulvan as immunonutrient in Solea senegalensis.

Immunonutrition is a promising and viable strategy for the development of prophylactic measures in aquaculture. Ulvan, a sulphated marine polysaccharide from green seaweeds, has many biological activities including the immunomodulatory ones. The aim of this study was to assess the short and long-term effects of an ulvan-rich extract obtained from U. ohnoi as immunonutrient in Senegalese sole juveniles. In this work, an ulvan-rich extract from Ulva ohnoi has been obtained by the hot water method and isolated by ethanol precipitation. The FTIR analysis revealed that the ulvan-rich extact had very similar characteristics to previously published ulvan spectra. The total sulfate and protein content was 24.85 ± 3.98 and 0.91 ± 0.04 %, respectively. In vitro assays performed in Senegalese sole (Solea senegalensis) macrophages showed that the ulvan obtained in this study did not compromise the cell viability at concentrations up to 1 mg ml-1 and expression levels of lyg, irf1, il6, il10, c7, tf and txn were significantly upregulated in a concentration dependent-manner. Finally, S. senegalensis juveniles were fed basal diets and diets supplemented with the ulvan-rich extract at ratios 1 and 2 % for 30 days and then, challenged with Photobacterium damselae subsp. piscicida (Phdp). Thereafter, ulvan was withdrawn from the diet and all juveniles were fed the basal diet for 30 days. At 30 days post withdrawal (dpw), juveniles were challenged with Phdp. The expression profiles of a set of genes related to the immune system in spleen were evaluated as well as the lysozyme, peroxidase and bactericidal activity in plasma. Dietary effects of 1 % ulvan resulted in a boost of the immune response and increased disease resistance at short-term whereas juveniles fed diets supplemented with 2 % ulvan showed a significant decrease in the bactericidal activity and lack of protection against Phdp. At long-term (30 days after the withdrawal of ulvan), an improved response was observed in juveniles previously fed 1 % ulvan.

Functionalization of seaweed bloom-derived Ulvan using response surface methodology with application in flocculation of oil-in-water pollution.

Utilizing macroalgal waste biomass for pollution management is a highly efficient method for addressing the environmental difficulties associated with its disposal. To accomplish this, we have attempted to synthesize a graft copolymer by combining ulvan, a sulfated polysaccharide isolated from seaweed, with acrylates. A one-pot synthesis method using UV-initiated graft polymerization with V-50 as the photoinitiator resulted in the production of a distinctive, high-performance, and eco-friendly flocculant, Ulvan-g-Poly (acrylamide-co-acrylic acid) referred as P(U_AAm_AAc). The synthesis was optimized using the CCD-RSM approach, employing molecular weight and inherent viscosity as indicators to optimize the parameters. The structural and physio-chemical properties of the synthesized P(U_AAm_AAc) were characterized utilizing XRD, ATR-FTIR, ζ-potential, and H1 NMR spectroscopy. The flocculation performance of P(U_AAm_AAc) was further examined for the removal of oils from samples with high neem oil in urea solution and low crude oil in seawater. By employing a coagulant-flocculant combination of poly-aluminium chloride (PAC) and P(U_AAm_AAc), it was noted that more than 94% of oil was effectively eliminated in both samples. Optimization of the dosage of P(U_AAm_AAc) resulted in enhanced turbidity reduction and improved dewatering efficiency of the filter cake generated following flocculation. An evaluation of performance was conducted using the commercial flocculant APAM, where synthesized P(U_AAm_AAc) demonstrated similar results. In conclusion, the findings of this research highlight the potential of P(U_AAm_AAc) as a sustainable alternative to commercial flocculants with multifaceted solution to coastal waste management, paving the way for a cleaner and healthier marine ecosystem to mitigate oil emulsion pollution.

Anti-Bacterial and Immunostimulatory Properties of Ulvan-Loaded Chitosan Nanoparticles for Use in Aquaculture.

Alternative prophylactic strategies to limit farm animal infection are needed in order to avoid the use of antibiotics. Anti-bacterial and immunostimulatory properties of bioactive compounds are of great interest in aquaculture. Marine derived polysaccharides, such as chitosan and ulvan, together with nanotechnology, have become the focus of attention in the scientific community due to their wide range of biological properties. In this work, chitosan and ulvan-loaded chitosan nanoparticles (referred as CS-TPP NPs and CS-UL-TPP NPs, respectively), obtained by the ionotropic gelation method, had round shape, and the mean sizes were 137.00 ± 5.44 and 325.50 ± 4.95 nm, respectively. No study about the anti-bacterial activity of both types of NPs against Photobacterium damselae subsp. piscicida, an important fish pathogen, has been reported so far. Furthermore, the potential immunostimulatory effects of CS-UL-TPP NPs after oral administration in fish have not yet been evaluated. The percentage of bacterial inhibition against P. damselae subsp. piscicida was determined through in vitro assays, and it was significantly higher in CS-UL-TPP NPs than in CS-TPP NPs at concentrations below 0.03 mg mL-1. The effects on the immune system of CS-TPP and CS-UL-TPP NPs were evaluated in Solea senegalensis juveniles at 30 days after oral administration. Lysozyme activity as well as gene expression levels of il1b, il6, hamp1, tf and c3 was significantly higher in CS-UL-TPP NP-treated groups than in the controls, and no significant differences were observed in CS-TPP NP-treated groups. Thus, ulvan extracted from the macroalgae Ulva ohnoi could improve anti-bacterial and immunostimulant properties of CS-TPP NPs thereby making them suitable to be used as vaccine adjuvant or as immunostimulant.

Structural Characterization and Cytotoxic Activity Evaluation of Ulvan Polysaccharides Extracted from the Green Algae Ulva papenfussii.

Ulvan, a sulfated heteropolysaccharide with structural and functional properties of interest for various uses, was extracted from the green seaweed Ulva papenfussii. U. papenfussii is an unexplored Ulva species found in the South China Sea along the central coast of Vietnam. Based on dry weight, the ulvan yield was ~15% (w/w) and the ulvan had a sulfate content of 13.4 wt%. The compositional constitution encompassed L-Rhamnose (Rhap), D-Xylose (Xylp), D-Glucuronic acid (GlcAp), L-Iduronic acid (IdoAp), D-Galactose (Galp), and D-Glucose (Glcp) with a molar ratio of 1:0.19:0.35:0.52:0.05:0.11, respectively. The structure of ulvan was determined using High-Performance Liquid Chromatography (HPLC), Fourier Transform Infrared Spectroscopy (FT-IR), and Nuclear Magnetic Resonance spectroscopy (NMR) methods. The results showed that the extracted ulvan comprised a mixture of two different structural forms, namely ("A3s") with the repeating disaccharide [→4)-ß-D-GlcAp-(1→4)-α-L-Rhap 3S-(1→]n, and ("B3s") with the repeating disaccharide [→4)-α-L-IdoAp-(1→4)-α-L-Rhap 3S(1→]n. The relative abundance of A3s, and B3s was 1:1.5, respectively. The potential anticarcinogenic attributes of ulvan were evaluated against a trilogy of human cancer cell lineages. Concomitantly, Quantitative Structure-Activity Relationship (QSAR) modeling was also conducted to predict potential adverse reactions stemming from pharmacological interactions. The ulvan showed significant antitumor growth activity against hepatocellular carcinoma (IC50 ≈ 90 µg/mL), human breast cancer cells (IC50 ≈ 85 µg/mL), and cervical cancer cells (IC50 ≈ 67 µg/mL). The QSAR models demonstrated acceptable predictive power, and seven toxicity indications confirmed the safety of ulvan, warranting its candidacy for further in vivo testing and applications as a biologically active pharmaceutical source for human disease treatment.

Enzyme-Assisted Extraction of Ulvan from the Green Macroalgae Ulva fenestrata.

Ulvan is a sulfated polysaccharide extracted from green macroalgae with unique structural and compositional properties. Due to its biocompatibility, biodegradability, and film-forming properties, as well as high stability, ulvan has shown promising potential as an ingredient of biopolymer films such as sustainable and readily biodegradable biomaterials that could replace petroleum-based plastics in diverse applications such as packaging. This work investigates the potential of Ulva fenestrata as a source of ulvan. Enzyme-assisted extraction with commercial cellulases (Viscozyme L and Cellulysin) and proteases (Neutrase 0.8L and Flavourzyme) was used for cell wall disruption, and the effect of the extraction time (3, 6, 17, and 20 h) on the ulvan yield and its main characteristics (molecular weight, functional groups, purity, and antioxidant capacity) were investigated. Furthermore, a combined process based on enzymatic and ultrasound extraction was performed. Results showed that higher extraction times led to higher ulvan yields, reaching a maximum of 14.1% dw with Cellulysin after 20 h. The combination of enzymatic and ultrasound-assisted extraction resulted in the highest ulvan extraction (17.9% dw). The relatively high protein content in U. fenestrata (19.8% dw) makes the residual biomass, after ulvan extraction, a potential protein source in food and feed applications.

Electrospun nanofiber composite mat based on ulvan for wound dressing applications.

Wound dressings can be used to create a temporary healing environment and expedite the wound healing process. Ulvan (ULV) is a sulfated polysaccharide with potent antiviral and anti-inflammatory activities. Polycaprolactone (PCL) is a hydrophobic biodegradable polyester that exhibits slow degradation, strong mechanical strength, and excellent biocompatibility. Electrospun nanofiber matrices mimic the microstructure of the extracellular matrix, allowing them to promote cell proliferation and differentiation. Therefore, the primary objective of this study was to fabricate a polycaprolactone-ulvan fibrous composite mat (PCL-ULV) using the electrospinning technique and to investigate its physical and chemical properties. To assess the characteristics of PCL-ULV, scanning electron microscopy (SEM) was utilized to examine its morphology and diameter distribution. Fourier transform infrared (FTIR) spectroscopy, calcofluor white staining, and monosaccharide analysis were employed to analyze the components of PCL-ULV. Additionally, the water contact angle was measured to evaluate the hydrophilicity. Furthermore, the proliferation and morphology of and gene expression in NIH3T3 fibroblasts on PCL-ULV were assessed. The results showed that the average PCL-ULV fiber diameter was significantly smaller than that of the PCL fibers. The water contact angle measurements indicated that PCL-ULV exhibited better hydrophilicity than the PCL mat. FTIR, calcofluor white staining, and monosaccharide analyses demonstrated that ULV could be successfully coelectrospun with PCL. NIH3T3 fibroblasts cultured on PCL and PCL-ULV showed different cellular behaviors. On PCL-ULV, cell adhesion, proliferation, and stretching were greater than those on PCL. Moreover, the behavior of NIH3T3 fibroblasts on PCL and PCL-ULV differed, as the cells on PCL-ULV exhibited higher proliferation and more stretching. Furthermore, NIH3T3 fibroblasts cultured on ULV-PCL showed higher α-SMA and MMP-9 gene expression and a lower ratio of TIMP-1/MMP-9 than those cultured on PCL. Notably, scarless wounds display lower TIMP/MMP expression ratios than scarring wounds. Thus, the fibrous composite mat PCL-ULV shows potential as a wound dressing for scarless wound healing.

Biochemical characterization of a new ulvan lyase and its applicability in utilization of ulvan and preparation of ulva oligosaccharides.

Ulva is globally distributed specie and has a high economic value. Ulvan is one of the main active substances in Ulva, which has a variety of biological properties. Ulvan lyase degrades ulvan through a ß-elimination mechanism which cleaves the ß-glycosidic bond between Rha3S and GlcA or IdoA. The complex monosaccharide composition of ulvan makes it promising for use in food and pharmaceutical applications. This thesis explores a putative ulvan lyase from Alteromonas sp. KUL_42. We expressed and purified the protein, performed a series of characterizations and signal peptide had been removed. The results showed that the protein molecular weight of ULA-2 was 53.97 kDa, and it had the highest catalytic activity at 45 °C and pH 8.0 in Tris-HCl buffer. The Km and Vmax values were 2.24 mg · mL-1 and 2.048 µmol · min-1 · mL-1, respectively. The activity of ULA-2 was able to maintain more than 80% at 20 ~ 30 °C. ESI-MS analysis showed that the primary end-products were mainly disaccharides to tetrasaccharides. The study of ULA-2 enriches the ulvan lyase library, promotes the development and high-value utilization of Ulva resources, and facilitates further research applications of ulvan lyase in ulva oligosaccharides.

Sustainable biorefining and bioprocessing of green seaweed (Ulva spp.) for the production of edible (ulvan) and non-edible (polyhydroxyalkanoate) biopolymeric films.

A sustainable biorefining and bioprocessing strategy was developed to produce edible-ulvan films and non-edible polyhydroxybutyrate films. The preparation of edible-ulvan films by crosslinking and plasticisation of ulvan with citric acid and xylitol was investigated using Fourier transform infrared (FTIR) spectroscopy and differential scanning calorimetry (DSC) analysis. The edible ulvan film was tested for its gut-friendliness using Lactobacillus and Bifidobacterium spp. (yoghurt) and was shown to improve these gut-friendly microbiome's growth and simultaneously retarding the activity of pathogens like Escherchia coli and Staphylococcus aureus. Green macroalgal biomass refused after the extraction of ulvan was biologically processed by dark fermentation to produce a maximum of 3.48 (± 0.14) g/L of volatile fatty acids (VFAs). Aerobic processing of these VFAs using Cupriavidus necator cells produced 1.59 (± 0.12) g/L of biomass with 18.2 wt% polyhydroxybutyrate. The present study demonstrated the possibility of producing edible and non-edible packaging films using green macroalgal biomass as the sustainable feedstock.

Ulvan/Silver nanoparticle hydrogel films for burn wound dressing.

Ulvan is a polysaccharide from green algae that shows good hydrogel film dressing characteristics. Silver nanoparticles (AgNP) can be incorporated into the hydrogel film to improve antibacterial properties and provide a potential burn treatment. In this study, we developed a novel hydrogel film wound dressing composed of ulvan and silver nanoparticles. Two concentrations (0.5 mM and 1 mM) of silver nitrate were used to produce ulvan-silver nanoparticles hydrogel film (UHF-AgNP0.5 and UHF-AgNP1), respectively. The physicochemical characteristics of the hydrogel films were evaluated, including particle size, zeta potential, Fourier transform infrared (FTIR), X-ray diffractometry (XRD), scanning electron microscope and energy-dispersive X-ray (SEM-EDX). Furthermore, the in vitro antimicrobial activity, and second-degree burn wound healing test were evaluated. The UHF-AgNP0.5 showed the highest antimicrobial activity compared to UHF-AgNP1 and UHF film. Meanwhile, an in vivo study using Wistar rats induced second-degree burns showed that UHF-AgNP0.5 significantly accelerated the healing process by regulating the inflammatory process, increasing re-epithelialization, and improving the vascularization process. Ulvan-silver nanoparticle hydrogel films have the ability to accelerate the healing of second-degree burns and are potential candidates for wound dressings.