Determination of Antioxidant, Antimicrobial Activity, Heavy Metals and Elements Content of Seaweed Extracts

Analysis of Heavy Metal Accumulation in Ulva rigida and its Effects on Seed Germination of Pennisetum glaucum

The alga contains salt and heavy metals that are accumulated in algae poses a significant challenge to the safe use of algae in soil fertilization and other applications. This study examines the relevance of algal biomass as an environmentally friendly fertilizer, thereby contributing to sustainable coastal management practices. In this study, the hot and cold extraction method were done to obtain the Ulva rigida extract. Heavy metals such as vanadium, chromium, manganese, iron, nickel, cobalt, copper, zinc and cadmium etc. were analyzed using ICP-MS. Heavy metal analysis showed that the major metals such as manganese, iron, vanadium and zinc in Ulva rigida extract. The algae extract was used in different concentration (20, 40, 60 and 80 μL) to analyze the seed germination study in Pennisetum glaucum and it was found that theseed germination were 100 % at 5th day after sowing and the root and shoot length increased with increasing concentration of Ulva rigida extract and at 80 μL the shoot length of Pennisetum glaucum were decreased. The aqueous extracts of Ulva rigida are eco-friendly, safe method for recycling the algal biomass as a novel biofertilizer.

Sargassum plagiophyllum Ethanolic Extract Enhances Wound Healing by Modulating FAK/Src/Akt/p38 and Rac1 Signaling in Keratinocytes HaCaT Cells

Recently, seaweed extracts have been found to have potential in skin benefits. This study, therefore, aimed to explore phytochemical analysis, antimicrobial, antioxidant, and wound healing properties of brown seaweed Sargassum plagiophyllym ethanolic extract (SPEE) on human skin keratinocyte HaCaT cells and the possible mechanism involved. Our results indicated that SPEE contained flavonoid, phenolic, and carotenoid as the major active constituents. The HPLC chromatogram revealed C-phycocyanin and fucoidan presented in SPEE. SPEE demonstrated the antioxidant capability and significantly reduced wound space at 24 and 48 h in wound-healing assay. Treatment with SPEE (50 and 100 μg/mL) increased FAK and Src phosphorylation in western blotting. Moreover, SPEE also upregulated Akt and p38 MAPK phosphorylation but not ERK1/2. SPEE increased Rac1 protein expression. Interestingly, hyaluronan synthase (HAS1 and HAS2) as well as collagen type I and elastin were also significantly upregulated when compared with the control upon exposure to SPEE. In conclusion, our data suggested that SPEE promotes cutaneous wound healing by regulating FAK/Src-mediated Akt, p38 MAPK, and Rac1 signaling. These findings suggest the potential use of SPEE for skin wound treatment.

Antimicrobial Activities of Polysaccharide-Rich Extracts from the Irish Seaweed Alaria esculenta, Generated Using Green and Conventional Extraction Technologies, Against Foodborne Pathogens

A rise in antimicrobial resistance coupled with consumer preferences towards natural preservatives has resulted in increased research towards investigating antimicrobial compounds from natural sources such as macroalgae (seaweeds), which contain antioxidant, antimicrobial, and anticancer compounds. This study investigates the antimicrobial activity of compounds produced by the Irish seaweed Alaria esculenta against Escherichia coli and Listeria innocua, bacterial species which are relevant for food safety. Microwave-assisted extraction (MAE), ultrasound-assisted extraction (UAE), ultrasound-microwave-assisted extraction (UMAE), and conventional extraction technologies (maceration) were applied to generate extracts from A. esculenta, followed by their preliminary chemical composition (total phenolic content, total protein content, total soluble sugars) and antimicrobial activity (with minimum inhibitory concentration determined by broth microdilution methods), examining also the molecular weight distribution (via high performance size exclusion chromatography) and oligosaccharide fraction composition (via high-performance liquid chromatography) of the polysaccharides, as they were the predominant compounds in these extracts, aiming to elucidate structure-function relationships. The chemical composition of the extracts demonstrated that they were high in total soluble sugars, with the highest total sugars being seen from the extract prepared with UAE, having 32.68 mg glucose equivalents/100 mg dried extract. Extracts had antimicrobial activity against E. coli and featured minimum inhibitory concentration (MIC) values of 6.25 mg/mL (in the case of the extract prepared with UAE) and 12.5 mg/mL (in the case of the extracts prepared with MAE, UMAE, and conventional maceration). No antimicrobial activity was seen by any extracts against L. innocua. An analysis of molar mass distribution of A. esculenta extracts showed high heterogeneity, with high-molecular-weight areas possibly indicating the presence of fucoidan. The FTIR spectra also indicated the presence of fucoidan as well as alginate, both of which are commonly found in brown seaweeds. These results indicate the potential of antimicrobials from seaweeds extracted using green technologies.

Chaetomorpha linum Extract as a Source of Antimicrobial Compounds: A Circular Bioeconomy Approach

The circular bioeconomy is currently a promising model for repurposing natural sources; these sources include plants due to their abundance of bioactive compounds. This study evaluated the antimicrobial properties of a Chaetomorpha linum extract. Chaetomorpha linum is an invasive macroalga from the Orbetello Lagoon (Tuscany, Italy), which grows in nutrient-rich environments and has been forming extended mats since 2005. The biomass is mechanically harvested and treated as waste, consuming considerable manpower and financial resources. As a potential way to increase the value of such waste, this study found that C. linum extract (CLE) is a source of antimicrobial compounds. The phytochemical characterization of the extract revealed the predominant presence of palmitic acid, a fatty acid with known antimicrobial activity. Based on such findings, four bacterial species of high clinical relevance (Enterococcus faecalis, Staphylococcus aureus, Pseudomonas aeruginosa, and Escherichia coli) were tested, revealing a notable antibacterial activity of the extract on Enterococcus faecalis (MIC, 32 μg/mL). Computational analyses identified a potential Enterococcus faecalis molecular target for palmitic acid, offering molecular insights on the interaction. This study presents a comprehensive in vitro and in silico approach for drug and target discovery studies by repurposing C. linum as a source of antimicrobial bioactive compounds.

In vitro antibacterial, antibiofilm activities, and phytochemical properties of Posidonia oceanica (L.) Delile: An endemic Mediterranean seagrass

In the antibiotic resistance era, utilizing understudied sources for novel antimicrobials or antivirulence agents can provide new advances against antimicrobial resistant pathogens. In this study, we aimed to investigate antibacterial and antibiofilm activities of Posidonia oceanica (L.) Delile against Enterococcus faecalis ATCC 29212, Staphylococcus aureus ATCC 25923, Escherichia coli ATCC 25922 and Klebsiella pneumoniae ATCC 700603 and several S. aureus clinical isolates obtained from medical devices, including patient urinary catheters and breast implant infections, with varying antibiotic recalcitrance profiles. The ethanolic and methanolic extracts from P. oceanica rhizome exhibited significant antibacterial activity against E. faecalis and S. aureus, as well as drug resistant S. aureus clinical isolates. Furthermore, significant antibiofilm activity was observed against S. aureus and E. faecalis treated with ER, MR1, and MR2. P. oceanica extracts also exhibited synergistic antimicrobial activity with ciprofloxacin against E. faecalis, sensitizing E. faecalis to a lower ciprofloxacin concentration. Collectively, our data demonstrate the selective antibacterial and antibiofilm activity of the extracts of P. oceanica against Gram-positive bacteria and clinical isolates along with potentiation of current antibiotics, which suggests that P. oceanica can be further investigated as a potential source for novel therapeutic options in the treatment of drug resistant bacterial infections.

Heavy metal tolerance, and metal biosorption by exopolysaccharides produced by bacterial strains isolated from marine hydrothermal vents

The present study highlights heavy metal tolerance, EPS production, and biosorption capacity of four hydrothermal vent bacterial strains, namely Exiguobacterium aquaticum, Mammaliicoccus sciuri, Micrococcus luteus, and Jeotgalicoccus huakuii against As, Cd, Cr, Cu, Co, Pb and Ni. The biosorption assay showed high removal efficiency of As (83%) by E. aquaticum, Cd (95%) by M. sciuri, Cu (94%) by M. luteus, and Ni (89%) by J. huakuii and their produced EPS with these metals in aqueous solution were 84%, 85%, 98%, and 91%, respectively. The maximum EPS yield was attained by optimized medium composition consisting of 1% Xylose, and 1% NaCl at pH 7. In metal-amended conditions, the four bacterial strains showed induced EPS production in the initial concentrations. SEM with EDX and CLSM images showed that the growth and EPS production of bacterial strains were affected by metal ion concentrations. A phenol sulphuric acid method and BCA assay were used to identify both the carbohydrate and total protein content of four extracted EPS. A DPPH assay revealed that EPS influences free radical scavenging and has a highly enhanced synergistic effect with its antioxidant activity. FT-IR analysis of four extracted EPS showed the shifting of peaks in the functional groups of EPS before and after adsorption of metal ions. At pH 5 and after 60 min contact time metal removal efficiency and adsorption capacity increased as calculated for As, Cd, Cu, and Ni by four extracted EPS: (86%, 20 mg/g), (74%, 19 mg/g), (94%, 60 mg/g) and (89%, 32 mg/g) and (89%, 16 mg/g), (85%, 16 mg/g), (96%, 22 mg/g) and (91%, 16 mg/g), respectively. The Langmuir compared to the Freundlich model was found to better represent the adsorption by EPS providing maximum adsorption capacities for As (34.65 mg/g), Cd (52.88 mg/g), Cu (24.91 mg/g), and Ni (58.38 mg/g).

Direct and robust citramalate production from brown macroalgae using fast-growing Vibrio sp. dhg

Brown macroalgae is a promising feedstock for biorefinery owing to its high biomass productivity and contents of carbohydrates such as alginate and mannitol. However, the limited availability of microbial platforms efficiently catabolizing the brown macroalgae sugars has restricted its utilization. In this study, the direct production of citramalate, an important industrial compound, was demonstrated from brown macroalgae by utilizing Vibrio sp. dhg, which has a remarkably efficient catabolism of alginate and mannitol. Specifically, citramalate synthase from Methanocaldococcus jannaschii was synthetically expressed, and competing pathways were removed to maximally redirect the carbon flux toward citramalate production. Notably, a resulting strain, VXHC, produced citramalate up to 9.8 g/L from a 20 g/L mixture of alginate and mannitol regardless of their ratios. Citramalate was robustly produced even when diverse brown macroalgae were provided directly. Collectively, this study showcased the high potential of brown macroalgae biorefinery using Vibrio sp. dhg.

Seaweeds in Food: Current Trends

Edible seaweeds are an excellent source of macronutrients, micronutrients, and bioactive compounds, and they can be consumed raw or used as ingredients in food products. However, seaweeds may also bioaccumulate potentially hazardous compounds for human health and animals, namely, heavy metals. Hence, the purpose of this review is to analyze the recent trends of edible seaweeds research: (i) nutritional composition and bioactive compounds, (ii) the use and acceptability of seaweeds in foodstuffs, (iii) the bioaccumulation of heavy metals and microbial pathogens, and (iv) current trends in Chile for using seaweeds in food. In summary, while it is evident that seaweeds are consumed widely worldwide, more research is needed to characterize new types of edible seaweeds as well as their use as ingredients in the development of new food products. Additionally, more research is needed to maintain control of the presence of heavy metals to assure a safe product for consumers. Finally, the need to keep promoting the benefits of seaweed consumption is emphasized, adding value in the algae-based production chain, and promoting a social algal culture.

Prediction Model of Soil Heavy Metal Content Based on Particle Swarm Algorithm Optimized Neural Network

In 2014, the relevant research data from the Ministry of Environmental Protection and the Ministry of Land and Resources showed that the total exceedance rate of soil heavy metal pollution in China had reached 16.1%, and in the construction of ecological civilization in the 13th Five-Year Plan, China has made the prevention and control of soil heavy metal pollution as the focus of prevention and control. Therefore, in this paper, four neural optimization network models, that is, radial basis neural network (RBFNN), generalized regression neural network (GRNN), wavelet neural network (WNN), and fuzzy neural network (FNN), are simulated and created to measure and correlate the soil heavy metal content in a city in northwest China and a city in central China from the actual situation in China. The simulations were conducted. Finally, by analyzing the comparison of predicted and true values of these four models on the test data of two sets of experimental data, the distribution of predicted differences to true values, and the calculation results of three error indicators, we found that WNN has the best prediction performance when using RBFNN, GRNN, WNN, and FNN for soil heavy metal content prediction.