Antimicrobial potential of macro and microalgae against pathogenic and spoilage microorganisms in food

Microalgae: A Promising Source of Bioactive Polysaccharides for Biotechnological Applications

Polysaccharides (PSs) are the most abundant carbohydrates in nature, performing essential biological functions such as immune system regulation, structural support, and cell communication. PSs from marine microalgae have gained increasing attention due to their diverse biological activities and potential applications in various fields, including the human health sector. These natural macromolecules, primarily composed of glucose, xylose, galactose, rhamnose, and fucose, exhibit bioactive properties influenced by their molecular weight, sulfation degree, and structural complexity. Microalgal PSs can function as antiviral, antimicrobial, antioxidant, immunomodulatory, and antitumor agents, making them promising candidates for pharmaceutical and nutraceutical applications. Additionally, their physicochemical properties make them valuable as bioactive ingredients in cosmetics, serving as hydrating agents, UV protectants, and anti-ageing compounds. The production of PSs from microalgae presents a sustainable alternative to terrestrial plants, as microalgae can be cultivated under controlled conditions, ensuring high yield and purity while minimizing environmental impact. Despite their potential, challenges remain in optimizing extraction techniques, enhancing structural characterization, and scaling up production for commercial applications. This review provides an overview of the principal biological activities of PSs from eukaryotic microalgae and their possible use as ingredients for cosmetic applications. Challenges to address to implement their use as products to improve human health and wellbeing are also discussed.

Phycochemistry and pharmacological significance of filamentous cyanobacterium Spirulina sp

The cyanobacterium, Spirulina sp. is a photosynthetic blue-green alga with essential nutrients, vitamins nucleic acids, proteins, carbohydrates, fatty acids and pigments carotenes; and phycocyanins are the significant components having immunomodulatory, anti-inflammatory properties, which are used in food and cosmetics industries. Spirulina sp. can play an important role in human and animal nutrition for potential health benefits due to their phycochemical and pharmaceutical significance. This study highlights antibacterial, antifungal, antiviral, antioxidant, nephroprotective, cardioprotective, anticancer, neuroprotective, anti-aging, anti-inflammatory, and immunomodulatory properties. It highlights anti-anemic, antidiabetic, probiotic, anti-malarial, anti-obesity and weight loss, anti-genotoxicity, anti-thrombic, radioprotective, and detoxifying effects of Spirulina sp. Pharmaceutical studies indicate it may improve heart health and add to the treatment of diabetes, obesity and weight loss. It can play a major role in protecting the environment by recycling wastewater and providing food for humans and animals. Spirulina sp. can supply ingredients for aquaculture and agricultural feeds, pigments, antioxidants, and essential omega-3 oils, among other human health and wellness products. The amino acid of Spirulina is among the greatest qualititavely of any plant, even higher than that of soybean. Furthermore, cyanobacterium Spirulina sp. could be a future antimicrobial drug agent.

The Multifaceted Applications of Seaweed and Its Derived Compounds in Biomedicine and Nutraceuticals: A Promising Resource for Future

The increasing demand for global food resources and over-dependence on terrestrial agroecosystems pose a significant challenge to the sustainable production of food commodities. Macroalgae are an essential source of food production in the marine environment, and their cultivation is a promising approach to alleviate the impending global food insecurity due to key factors, such as independence from terrestrial agriculture, rapid growth rate, unique biochemical composition, and carbon capture potential. Moreover, in many countries, seaweed has been used as food for decades because of its health and nutritional benefits. Seaweed contains bioactive components that are beneficial against various pathological conditions, including cancer, type 2 diabetes, and neurological disorders. Furthermore, the natural products derived from macroalgae have also been found to have immunostimulatory and antimicrobial properties. Macroalgae are also a significant source of rare sugars such as L-fucose, L-rhamnose, and glucuronic acid. Besides sugars, other bioactive components have been widely reported for their potential in cosmeceuticals. We have outlined the nutrient composition and functional properties of different species of macroalgae, with an emphasis on their potential as value-added products to the functional food market. Beyond being nutritional powerhouses, the variety of biological activities in human health and biomedicine makes them excellent candidates for developing novel drugs. Therefore, this review summarizes the pharmaceutical applications of macroalgae and suggests potential strategies for incorporating macroalgae-derived bioactive compounds into therapeutic products.

Seaweed in the Diet as a Source of Bioactive Metabolites and a Potential Natural Immunity Booster: A Comprehensive Review

Seaweed plays an essential role in the survival of marine life, provides habitats and helps in nutrient recycling. It is rich in valuable nutritious compounds such as pigments, proteins, polysaccharides, minerals, vitamins, omega-rich oils, secondary metabolites, fibers and sterols. Pigments like fucoxanthin and astaxanthin and polysaccharides like laminarin, fucoidan, galactan and ulvan possess immune-modulatory and immune-enhancing properties. Moreover, they show antioxidative, antidiabetic, anticancer, anti-inflammatory, antiproliferative, anti-obesity, antimicrobial, anticoagulation and anti-aging properties and can prevent diseases such as Alzheimer's and Parkinson's and cardiovascular diseases. Though seaweed is frequently consumed by Eastern Asian countries like China, Japan, and Korea and has gained the attention of Western countries in recent years due to its nutritional properties, its consumption on a global scale is very limited because of a lack of awareness. Thus, to incorporate seaweed into the global diet and to make it familiar as a functional food, issues such as large-scale cultivation, processing, consumer acceptance and the development of seaweed-based food products need to be addressed. This review is intended to give a brief overview of the present status of seaweed, its nutritional value and its bioactive metabolites as functional foods for human health and diseases owing to its immunity-boosting potential. Further, seaweed as a source of sustainable food and its prospects along with its issues are discussed in this review.

Algae and Cyanobacteria Fatty Acids and Bioactive Metabolites: Natural Antifungal Alternative Against Fusarium sp

Fungal diseases caused by Fusarium spp. significantly threaten food security and sustainable agriculture. One of the traditional strategies for eradicating Fusarium spp. incidents is the use of chemical and synthetic fungicides. The excessive use of these products generates environmental damage and has negative effects on crop yield. It puts plants in stressful conditions, kills the natural soil microbiome, and makes phytopathogenic fungi resistant. Finally, it also causes health problems in farmers. This drives the search for and selection of natural alternatives, such as bio-fungicides. Among natural products, algae and cyanobacteria are promising sources of antifungal bio-compounds. These organisms can synthesize different bioactive molecules, such as fatty acids, phenolic acids, and some volatile organic compounds with antifungal activity, which can damage the fungal cell membrane that surrounds the hyphae and spores, either by solubilization or by making them porous and disrupted. Research in this area is still developing, but significant progress has been made in the identification of the compounds with potential for controlling this important pathogen. Therefore, this review focuses on the knowledge about the mechanisms of action of the fatty acids from macroalgae, microalgae, and cyanobacteria as principal biomolecules with antifungal activity, as well as on the benefits and challenges of applying these natural metabolites against Fusarium spp. to achieve sustainable agriculture.

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.

Assessment of the antibacterial and antioxidant activities of seaweed-derived extracts

In swine farming, animals develop diseases that require the use of antibiotics. In-feed antibiotics as growth promoters have been banned due to the increasing concern of antimicrobial resistance. Seaweeds offer bioactive molecules with antibacterial and antioxidant properties. The aim was to estimate the in vitro properties of seaweed extracts: Ascophyllum nodosum (AN), Palmaria palmata (PP), Ulva lactuca (UL), and 1:1 mixes (ANPP, ANUL, PPUL). Escherichia coli strains were used to test for growth inhibitory activity, and chemical-based assays were performed for antioxidant properties. The treatments were 2 (with/without Escherichia coli) × 2 (F4 + and F18 +) × 5 doses (0, 1.44, 2.87, 5.75, 11.50, and 23.0 mg/mL). Bacteria were supplemented with seaweed extracts, and growth was monitored. The antioxidant activity was assessed with 6 doses (0, 1, 50, 100, 200, 500, and 600 mg/mL) × 6 compounds using two chemical assays. Data were evaluated through SAS. The results showed that AN and UL significantly inhibited (p < 0.05) the growth of F4 + and F18 +. PP and mixes did not display an inhibition of the bacteria growth. AN, PP, UL extracts, and mixes exhibited antioxidant activities, with AN showing the strongest dose-response. Thus, AN and UL seaweed extracts reveal promising antibacterial and antioxidant effects and may be candidates for in-feed additives.

Natural antibiotics against antimicrobial resistance: sources and bioinspired delivery systems

The current burden associated to multidrug resistance, and the emerging superbugs, result in a decreased and even loss of antibiotic efficacy, which poses significant challenges in the treatment of infectious diseases. This situation has created a high demand for the discovery of novel antibiotics that are both effective and safe. However, while antibiotics play a crucial role in preventing and treating diseases, they are also associated with adverse effects. The emergence of multidrug-resistant and the extensive appearance of drug-resistant microorganisms, has become one of the major hurdles in healthcare. Addressing this problem will require the development of at least 20 new antibiotics by 2060. However, the process of designing new antibiotics is time-consuming. To overcome the spread of drug-resistant microbes and infections, constant evaluation of innovative methods and new molecules is essential. Research is actively exploring alternative strategies, such as combination therapies, new drug delivery systems, and the repurposing of existing drugs. In addition, advancements in genomic and proteomic technologies are aiding in the identification of potential new drug targets and the discovery of new antibiotic compounds. In this review, we explore new sources of natural antibiotics from plants, algae other sources, and propose innovative bioinspired delivery systems for their use as an approach to promoting responsible antibiotic use and mitigate the spread of drug-resistant microbes and infections.

A comprehensive review on novel synthetic foods: Potential risk factors, detection strategies, and processing technologies

Nowadays, the food industry is facing challenges due to the simultaneous rise in global warming, population, and food consumption. As the integration of synthetic biology and food science, novel synthetic foods have obtained high attention to address these issues. However, these novel foods may cause potential risks related to human health. Four types of novel synthetic foods, including plant-based foods, cultured meat, fermented foods, and microalgae-based foods, were reviewed in the study. The original food sources, consumer acceptance, advantages and disadvantages of these foods were discussed. Furthermore, potential risk factors, such as nutritional, biological, and chemical risk factors, associated with these foods were described and analyzed. Additionally, the current detection methods (e.g., enzyme-linked immunosorbent assay, biosensors, chromatography, polymerase chain reaction, isothermal amplification, and microfluidic technology) and processing technologies (e.g., microwave treatment, ohmic heating, steam explosion, high hydrostatic pressure, ultrasound, cold plasma, and supercritical carbon dioxide) were reviewed and discussed critically. Nonetheless, it is crucial to continue innovating and developing new detection and processing technologies to effectively evaluate these novel synthetic foods and ensure their safety. Finally, approaches to enhance the quality of these foods were briefly presented. It will provide insights into the development and management of novel synthetic foods for food industry.

Antimicrobial Activity of Arthrospira (Former Spirulina) and Dunaliella Related to Recognized Antimicrobial Bioactive Compounds

With the increasing rate of the antimicrobial resistance phenomenon, natural products gain our attention as potential drug candidates. Apart from being used as nutraceuticals and for biotechnological purposes, microalgae and phytoplankton have well-recognized antimicrobial compounds and proved anti-infectious potential. In this review, we comprehensively outline the antimicrobial activity of one genus of cyanobacteria (Arthrospira, formerly Spirulina) and of eukaryotic microalgae (Dunaliella). Both, especially Arthrospira, are mostly used as nutraceuticals and as a source of antioxidants for health supplements, cancer therapy and cosmetics. Their diverse bioactive compounds provide other bioactivities and potential for various medical applications. Their antibacterial and antifungal activity vary in a broad range and are strain specific. There are strains of Arthrospira platensis with very potent activity and minimum inhibitory concentrations (MICs) as low as 2-15 µg/mL against bacterial fish pathogens including Bacillus and Vibrio spp. Arthrospira sp. has demonstrated an inhibition zone (IZ) of 50 mm against Staphylococcus aureus. Remarkable is the substantial amount of in vivo studies of Arthrospira showing it to be very promising for preventing vibriosis in shrimp and Helicobacter pylori infection and for wound healing. The innovative laser irradiation of the chlorophyll it releases can cause photodynamic destruction of bacteria. Dunaliella salina has exhibited MIC values lower than 300 µg/mL and an IZ value of 25.4 mm on different bacteria, while Dunaliella tertiolecta has demonstrated MIC values of 25 and 50 μg/mL against some Staphylococcus spp. These values fulfill the criteria for significant antimicrobial activity and sometimes are comparable or exceed the activity of the control antibiotics. The bioactive compounds which are responsible for that action are fatty acids including PUFAs, polysaccharides, glycosides, peptides, neophytadiene, etc. Cyanobacteria, such as Arthrospira, also particularly have antimicrobial flavonoids, terpenes, alkaloids, saponins, quinones and some unique-to-them compounds, such as phycobiliproteins, polyhydroxybutyrate, the peptide microcystin, etc. These metabolites can be optimized by using stress factors in a two-step process of fermentation in closed photobioreactors (PBRs).

Study of the Antimicrobial Potential of the Arthrospira platensis, Planktothrix agardhii, Leptolyngbya cf. ectocarpi, Roholtiella mixta nov., Tetraselmis viridis, and Nanofrustulum shiloi against Gram-Positive, Gram-Negative Bacteria, and Mycobacteria

The incidence of diseases brought on by resistant strains of micro-organisms, including tuberculosis, is rising globally as a result of the rapid rise in pathogenic micro-organism resistance to antimicrobial treatments. Secondary metabolites with potential for antibacterial activity are produced by cyanobacteria and microalgae. In this study, gram-positive (S. aureus, E. faecalis) and gram-negative (K. pneumoniae, A. baumannii, P. aeruginosa) bacteria were isolated from pulmonary tuberculosis patients receiving long-term antituberculosis therapy. The antimicrobial potential of extracts from the cyanobacteria Leptolyngbya cf. ectocarpi, Planktothrix agardhii, Arthrospira platensis, Rohotiella mixta sp. nov., Nanofrustulum shiloi, and Tetraselmis (Platymonas) viridis Rouchijajnen was evaluated. On mouse splenocytes and peritoneal macrophages, extracts of cyanobacteria and microalgae had inhibitory effects. In vitro studies have shown that cyanobacteria and microalgae extracts suppress the growth of bacteria and mycobacteria. At the same time, it has been demonstrated that cyanobacterial and microalgal extracts can encourage bacterial growth in a test tube. Additionally, the enhanced fucoxanthin fraction significantly reduced the development of bacteria in vitro. In a mouse experiment to simulate tuberculosis, the mycobacterial load in internal organs was considerably decreased by fucoxanthin. According to the information gathered, cyanobacteria and microalgae are potential sources of antibacterial compounds that can be used in the manufacturing of pharmaceutical raw materials.

The potential of microalgal sources as coating materials: A case study for the development of biocompatible surgical sutures

Sutures are considered as surgical materials that form excellent surfaces to integrate the postoperative parts of the body. These materials present suitable platforms for potential bacterial penetrations. Therefore, coating these biomedical materials with biocompatible compounds is seen as a potential approach to improve their properties while avoiding adverse effects. The aim of this study was to evaluate Arthrospira platensis, Haematacoccus pluvialis, Chlorella minutissima, Botyrococcus braunii, and Nostoc muscorum as potential surgical suture coating materials. Their crude extracts were absorbed into two different sutures as poly glycolic (90%)-co-lactic acid (10%) (PGLA) and poly dioxanone (PDO); then, their cytotoxic effects and antibacterial activities were examined. Both N. muscorum-coated sutures (PGLA and PDO) and A. platensis-coated (PGLA and PDO) sutures did not induce any toxic effect on L929 mouse fibroblast cells (>70% cell viability). The highest antibacterial activity against Staphylococcus aureus was achieved with N. muscorum-coated PGLA and A. platensis-coated PGLA at 11.18 ± 0.54 mm and 9.52 ± 1.15 mm, respectively. These sutures were examined by mechanical analysis, and found suitable according to ISO 10993-5. In comparison with the commercial antibacterial agent (chlorohexidine), the results proved that N. muscorum extract can be considered as the most promising suture coating material for the human applications.

Biotechnological product potential of Auxenochlorella protothecoides including biologically active compounds (BACs) under nitrogen stress conditions

Nitrogen stress can influence microalgae's growth characteristics, and microalgae grown in nitrogen-deficient conditions may produce higher or lower levels of biotechnological products as a result of metabolic changes. In photoautotrophic and heterotrophic cultures, nitrogen limitation has been proven effective in promoting lipid accumulation. In spite of this, no study has demonstrated a significant correlation between lipid content and other biotechnological products such as bioactive compounds (BACs). This research examines a strategy for lipid accumulation as well as the potential production of BACs with antibacterial properties in parallel with that strategy. This concept involved the treatment of the microalga Auxenochlorella protothecoides with low and high concentrations of ammonium (NH₄⁺). This particular experiment reached a maximum lipid content of 59.5% using a 0.8 mM NH₄⁺ concentration, resulting in the yellowing of the chlorophyll levels. Agar diffusion assays were conducted to determine the antibacterial activity of different extracts derived from the biomass when stressed with different levels of nitrogen. Algal extracts prepared by a variety of solvents showed different levels of antibacterial activity against representative strains of both gram-negative (Escherichia coli) and gram-positive (Staphylococcus aureus) bacteria. Among the extracts tested, 500 mg/L ethyl acetate extract had the greatest antibacterial activity against Escherichia coli. In order to identify the components responsible for the extract's antibacterial activity, fatty acid methyl ester (FAME) analysis was performed. It has been suggested that the lipid fraction may be a valuable indicator of these activities since some lipid components are known to possess antimicrobial properties. In this regard, it was found that the amount of polyunsaturated fatty acid (PUFA) significantly decreased by 53.4% under the conditions with the highest antibacterial activity observed.

Antimicrobial therapeutics isolated from algal source: retrospect and prospect

In the last few decades, attention on new natural antimicrobial compounds has arisen due to a change in consumer preferences and the increase in the number of resistant microorganisms. Algae are defined as photosynthetic organisms that demonstrate a wide range of adaptability to adverse environmental conditions like temperature extremes, photo-oxidation, high or low salinity, and osmotic stress. Algae are primarily known to produce large amounts of secondary metabolite against various kinds of pathogenic microbes. Among these algae, micro and microalgae of river, lake, and algae of oceanic origin have been reported to have antimicrobial activity against the bacteria and fungi of pathogenic nature. Various polar and non- polar extracts of micro- and macro algae have been used for the suppression of these pathogenic fungi. Apart from these, certain algal derivatives have also been isolated from these having antibacterial and antifungal potential. Among the bioactive molecules of algae, polysaccharides, sulphated polysaccharides, phyco-cyanobilins polyphenols, lectins, proteins lutein, vitamin E, B₁₂ and K₁, peptides, polyunsaturated fatty acids and pigments can be highlighted. In the present review, we will discuss the biological activity of these derived compounds as antifungal/ antibacterial agents and their most promising applications. A brief outline is also given for the prospects of these isolated phytochemicals and using algae as therapeutic in the dietary form. We have also tried to answer whether alga-derived metabolites can serve as potential therapeutics for the treatment of SARS-CoV-2 like viral infections too.

Skin Health Promoting Effects of Natural Polysaccharides and Their Potential Application in the Cosmetic Industry

Skincare is one of the most profitable product categories today. Consumers’ demand for skin-friendly products has stimulated the development of natural-ingredient-based cosmeceutical preparations over synthetic chemicals. Thus, natural polysaccharides have gained much attention since the promising potent efficacy in wound healing, moisturizing, antiaging, and whitening. The challenge is to raise awareness of polysaccharides with excellent bioactivities from natural sources and consequently incorporate them in novel and safer cosmetics. This review highlights the benefits of natural polysaccharides from plants, algae, and fungi on skin health, and points out some obstacles in the application of natural polysaccharides.

Study of the Physicochemical and Biological Properties of the Lipid Complex of Marine Microalgae Isolated from the Coastal Areas of the Eastern Water Area of the Baltic Sea

The Baltic Sea algae species composition includes marine euryhaline, freshwater euryhaline, and true brackish water forms. This study aimed to isolate a lipid–pigment complex from microalgae of the Baltic Sea (Kaliningrad region) and investigate its antimicrobial activity against Gram-positive and Gram-negative bacteria. Microalgae were sampled using a box-shaped bottom sampler. Sequencing was used for identification. Spectroscopy and chromatography with mass spectroscopy were used to study the properties of microalgae. Antibiotic activity was determined by the disc diffusion test. Lipids were extracted using the Folch method. Analysis of the results demonstrated the presence of antimicrobial activity of the lipid–pigment complex of microalgae against E. coli (the zone diameter was 17.0 ± 0.47 mm and 17.0 ± 0.21 mm in Chlorella vulgaris and Arthrospira platensis, respectively) and Bacillus pumilus (maximum inhibition diameter 16.0 ± 0.27 mm in C. vulgaris and 16.0 ± 0.22 mm in A. platensis). The cytotoxic and antioxidant activities of the lipid complexes of microalgae C. vulgaris and A. platensis were established and their physicochemical properties and fatty acid composition were studied. The results demonstrated that the lipid–pigment complex under experimental conditions was the most effective against P. pentosaceus among Gram-positive bacteria. Antimicrobial activity is directly related to the concentration of the lipid–pigment complex. The presence of antibacterial activity in microalgae lipid–pigment complexes opens the door to the development of alternative natural preparations for the prevention of microbial contamination of feed. Because of their biological activity, Baltic Sea microalgae can be used as an alternative to banned antibiotics in a variety of fields, including agriculture, medicine, cosmetology, and food preservation.

Identification of Metabolites with Antibacterial Activities by Analyzing the FTIR Spectra of Microalgae

Biologically active substances from microalgae can exhibit antioxidant, immunostimulating, antibacterial, antiviral, antitumor, antihypertensive, regenerative, and neuroprotective effects. Lipid complexes of microalgae Chlorella vulgaris and Arthrospira platensis exhibit antibacterial activity and inhibit the growth of the Gram-positive strain Bacillus subtilis; the maximum zone of inhibition is 0.7 ± 0.03 cm at all concentrations. The carbohydrate-containing complex of C. vulgaris exhibits antibacterial activity, inhibits the growth of the Gram-positive strain B. subtilis, Bacillus pumilus; the maximum zone of inhibition is 3.5 ± 0.17 cm at all concentrations considered. The carbohydrate complex of A. platensis has antimicrobial activity against the Gram-negative strain of Escherichia coli at all concentrations, and the zone of inhibition is 2.0–3.0 cm. The presence of mythelenic, carbonyl groups, ester bonds between fatty acids and glycerol in lipid molecules, the stretching vibration of the phosphate group PO₂, neutral lipids, glyco- and phospholipids, and unsaturated fatty acids, such as γ-linolenic, was revealed using FTIR spectra. Spectral peaks characteristic of saccharides were found, and there were cellulose and starch absorption bands, pyranose rings, and phenolic compounds. Both algae in this study had phenolic and alcohol components, which had high antibacterial activity. Microalgae can be used as biologically active food additives and/or as an alternative to antibiotic feed in animal husbandry due to their antibacterial properties.

Potential anti-skin aging effect of a peptide AYAPE isolated from Isochrysis zhanjiangensis on UVB-induced HaCaT cells and H2O2-induced BJ cells

AYAPE (Ala-Tyr-Ala-Pro-Glu) is a pentapeptide isolated from Isochrysis zhanjiangensis, previous studies have proved that this pentapeptide has antioxidant and inflammatory activities. In this study, we determined the anti-skin aging bioactivity of AYAPE with UVB-induced human immortalized keratinocytes (HaCaT) and H₂O₂-induced human skin fibroblasts (BJ cells) as models. The results showed that AYAPE against UVB-induced photoaging on HaCaT cells via alleviating DNA damage, reducing intracellular reactive oxygen (ROS) levels, down regulating phosphorylation of proteins in MAPK/AP-1 signaling pathways. In addition, AYAPE attenuated senescence related effectors expression in H₂O₂-induced BJ cells. Furthermore, p53 showed an important role in regulation effect of AYAPE in both two cells, and AYAPE showed a directly combination with p53 by molecular docking. These results demonstrated that AYAPE is potential to against skin aging by decreasing matrix metalloproteinase-1 (MMP-1) production, inhibiting inflammation and apoptosis, and attenuating fibroblast senescence.

Antioxidant and Antimicrobial Activity of Algal and Cyanobacterial Extracts: An In Vitro Study

Algae and cyanobacteria, other than their nutritional value, possess different beneficial properties, including antioxidant and antimicrobial ones. Therefore, they can be considered functional ingredients in animal feed and natural substitutes for antibiotics. The aim of this study was to evaluate the antioxidant and antimicrobial capacity against porcine O138 E. coli of Ascophyllum nodosum, Chlorella vulgaris, Lithotamnium calcareum, Schizochytrium spp. as algal species and Arthrospira platensis as cyanobacteria. The antioxidant capacity was determined by ABTS Radical Cation Decolorization Assay testing at three different concentrations (100%; 75%; 50%). The growth inhibition effect of the extracts at concentrations of 25%, 12.5%, 6%, 3% and 1.5% against porcine O138 E. coli was genetically characterized by PCR to detect the presence of major virulence factors; this was evaluated by following the microdilution bacterial growth method. The ABTS assay disclosed that Ascophyllum nodosum was the compound with the major antioxidant properties (57.75 ± 1.44 percentage of inhibition; p < 0.0001). All the extracts tested showed growth inhibition activity at a concentration of 25%. Among all extracts, A. nodosum was the most effective, showing a significant growth inhibition of E. coli; in particular, the log10 cells/mL of E. coli used as a control resulted in a significantly higher concentration of 25% and 12.5% after 4 h (8.45 ± 0.036 and 7.22 ± 0.025 log10 cells/mL, respectively; p < 0.005). This also suggests a dose-dependent relationship between the inhibitory activity and the concentration. Also, a synergistic effect was observed on antioxidant activity for the combination of Ascophyllum nodosum and Lithotamnium calcareum (p < 0.0001). Moreover, to determine if this combination could affect the viability of the IPEC-J2 cells under the normal or stress condition, the viability and membrane integrity were tested, disclosing that the combination mitigated the oxidative stress experimentally induced by increasing the cell viability. In conclusion, the results obtained highlight that the bioactive compounds of algal species are able to exert antioxidant capacity and modulate O138 E. coli growth. Also, the combination of Ascophyllum nodosum and Lithotamnium calcareum species can enhance their bioactivity, making them a promising functional feed additive and a suitable alternative to antibiotics.

Influence of Processing Parameters and Natural Antimicrobial on Alicyclobacillus acidoterrestris and Clostridium pasteurianum Using Response Surface Methodology

The food industry must ensure the stability of the products, and this is often achieved by exposing foods to heat treatments that are able to ensure the absence of pathogenic or spoilage microorganisms. These treatments are different in terms of temperature and duration and could lead to a loss in nutritional and sensory value. Moreover, some types of microorganisms manage to survive these treatments thanks to the sporification process. The addition of antimicrobials can become necessary, but at present, consumers are more inclined toward natural products, avoiding synthetic and chemical additives. Antimicrobials from plants could be a valuable option and, in this context, a patent concerning an antimicrobial extract from fermented plant substrate was recently tested against foodborne pathogens revealing high antimicrobial activity. The objective of this study was the creation of a model for the evaluation and subsequent prediction of the combined effect of different process and product variables, including antimicrobial addition, on the inhibition and reduction of spore germination of target microorganisms, Alicyclobacillus acidoterrestris and Clostridium pasteurianum, responsible for spoilage of tomato-based products.

Microalgal drugs: A promising therapeutic reserve for the future

Over the decades, a variety of chemically synthesized drugs are being used to cure existing diseases but often these drugs could not be effectively employed for the treatment of serious and newly emerging diseases. Fortunately, in nature there occurs immense treasure of plants and microorganisms which are living jewels with respect to their richness of medically important metabolites of high value. Hence, amongst the existing microorganism(s), the marine world offers a plethora of biological entities that can contribute to alleviate numerous human ailments. Algae are one such photosynthetic microorganism found in both marine as well as fresh water which are rich source of metabolites known for their nutrient content and health benefits. Various algal species like Haematococcus, Diatoms, Griffithsia, Chlorella, Spirulina, Ulva, etc. have been identified and isolated to produce biologically active and pharmaceutically important high value compounds like astaxanthin, fucoxanthin, sulphur polysaccharides mainly galactose, rhamnose, xylose, fucose etc., which show antimicrobial, antifungal, anti-cancer, and antiviral activities. However, the production of either of these bio compounds is favored under conditions of stress. This review gives detailed information on various nutraceutical metabolites extracted from algae. Additionally focus has been made on the role of these bio compounds extracted from algae especially sulphur polysaccharides to treat several diseases with prospective treatment for SARS-CoV-2. Lastly it covers the knowledge gaps and future perspectives in this area of research.

Bioprospecting of Microalgae Isolated from the Adriatic Sea: Characterization of Biomass, Pigment, Lipid and Fatty Acid Composition, and Antioxidant and Antimicrobial Activity

Marine microalgae and cyanobacteria are sources of diverse bioactive compounds with potential biotechnological applications in food, feed, nutraceutical, pharmaceutical, cosmetic and biofuel industries. In this study, five microalgae, Nitzschia sp. S5, Nanofrustulum shiloi D1, Picochlorum sp. D3, Tetraselmis sp. Z3 and Tetraselmis sp. C6, and the cyanobacterium Euhalothece sp. C1 were isolated from the Adriatic Sea and characterized regarding their growth kinetics, biomass composition and specific products content (fatty acids, pigments, antioxidants, neutral and polar lipids). The strain Picochlorum sp. D3, showing the highest specific growth rate (0.009 h⁻¹), had biomass productivity of 33.98 ± 0.02 mg L⁻¹ day⁻¹. Proteins were the most abundant macromolecule in the biomass (32.83–57.94%, g g⁻¹). Nanofrustulum shiloi D1 contained significant amounts of neutral lipids (68.36%), while the biomass of Picochlorum sp. D3, Tetraselmis sp. Z3, Tetraselmis sp. C6 and Euhalothece sp. C1 was rich in glycolipids and phospholipids (75%). The lipids of all studied microalgae predominantly contained unsaturated fatty acids. Carotenoids were the most abundant pigments with the highest content of lutein and neoxanthin in representatives of Chlorophyta and fucoxanthin in strains belonging to the Bacillariophyta. All microalgal extracts showed antioxidant activity and antimicrobial activity against Gram-negative E. coli and S. typhimurium and Gram-positive S. aureus.

Artificial intelligence-based approaches for modeling the effects of spirulina growth mediums on total phenolic compounds

Spirulina is a microalga and its phenolic compound is affected by growth mediums. In this study, Artificial intelligence (AI) based models, namely the Adaptive-Neuro Fuzzy Inference System (ANFIS) and Multilayer perceptron (MLP) models, and Step-Wise-Linear Regression (SWLR) were used to predict total phenolic compounds (TPC) of the spirulina algae. Spirulina productivity (P), extraction yield (EY), total flavonoids (TF), percent of flavonoid (%F) and percent of phenols (%P) are considered as input variables with the corresponding TPC as an output variable. From the result, TPC has a high positive correlation with the input variables with R = 0.99999. Also, the models showed that the ANFIS and SWLR gives superior result in the testing phase and increased its accuracy by 2% compared to MLP model in the prediction of TPC.

In vivo Assessment of Cold Atmospheric Pressure Plasma Technology on the Bioactivity of Spirulina

The present study challenges the in vivo assessment of cold atmospheric pressure plasma (CAPP) technology on the bioactive activity (antioxidant/antiaging and antimicrobial potential) of Spirulina powder, using Caenorhabditis elegans as an animal model. Surface microdischarge cold atmospheric pressure plasma (SMD-CAPP) treatment was 3.3 W discharge power for 7 min. C. elegans lifespan and egg laying were used as indicators of antioxidant/antiaging potential of Spirulina (1 mg/mL), when grown with Spirulina CP-treated [E_SCP] and untreated [E_S], compared with a control [E_0] (non-supplemented with Spirulina). According to our results, under both Spirulina supplemented media [E_SCP and E_S] and for the first 17 days, nematodes experienced an increase in lifespan but without significant differences (p > 0.05) between control and Spirulina CP-treated. Regarding the in vivo assay of the antimicrobial potential of Spirulina against Salmonella enterica serovar Typhimurium (infected worms), no significant differences (p > 0.05) were found between the three exposure scenarios (control [S_0]; Spirulina supplemented media [S_S]; CP-treated Spirulina supplemented media [S_SCP]). According to present results, CAPP-treatment do not influence negatively the lifespan of C. elegans but a reduction in the Spirulina antiaging potential was found. No in vivo modifications in antimicrobial activity seem to be linked to CAPP-processed Spirulina.

Prospects of Exploring the Metal-Organic Framework for Combating Antimicrobial Resistance

Infectious diseases are a major public health concern globally. Infections caused by pathogens with resistance against commonly used antimicrobial drugs or antibiotics (known as antimicrobial resistance, AMR) are becoming extremely difficult to control. AMR has thus been declared as one of the top 10 global public health threats, as it has very limited solutions. The drying pipeline of effective antibiotics has further worsened the situation. There is no absolute treatment, and the limitations of existing methods warrant further development in antimicrobials. Recent developments in the nanomaterial field present them as promising therapeutics and effective alternative to conventional antibiotics and synthetic drugs. The metal-organic framework (MOF) is a recent addition to the antimicrobial category with superior properties. The MOF exerts antimicrobial action on a wide range of species and is highly biocompatible. Additionally, their porous structures allow the incorporation of biomolecules and drugs for synergistic antimicrobial action. This review provides an inclusive summary of the molecular events responsible for resistance development and current trends in antimicrobials to combat antibiotic resistance and explores the potential role of the MOF in tackling the drug-resistant microbial species.

Marine algae as efficacious bioresources housing antimicrobial compounds for preserving foods - A review

Certain synthetic chemicals used in global food industries eliminate pathogenic food microbes and prevent spoilage. Nevertheless, their toxicity precludes human consumption. This phenomenon has made scientific fraternity to look for alternative antimicrobial compounds from natural resources. In recent times, marine algae have been illustrated to be potent and rich sources of antimicrobial agents as chemical replacements for applications in food. Identifying novel antimicrobial agents from natural resources have become a worldwide research with immense significance. Marine algae are now considered as one of the most inexhaustible and unexposed sources of antimicrobial agents due to their abundance in seawaters and renewability. This review elaborated on marine algal antimicrobial agents against foodborne pathogens, mode of action and cumulated the prospective use of algal compounds in active food packaging as a natural food preservative. Due to poor solubility, unpleasant odor and ineffectiveness of plant derived antimicrobial agents against Gram-negative bacteria, researchers opted for marine algae, an ideal candidate to be used as natural food preservatives. This article elaborates and summarizes the efficient bioactive molecules in marine algae and their possible application in food preservation to extend shelf life of foods without causing any toxicity. In conclusion, marine algae have potential antimicrobial property against food pathogens and have more advantages than other natural sources of antimicrobial agents.

Microalgae produced during phycoremediation of swine wastewater contains effective bacteriostatic compounds against antibiotic-resistant bacteria

Studies on the antimicrobial effects of microalgae extracts are commonly reported using algae biomass grown in sterile synthetic mineral medium and controlled laboratory conditions. However, variations in environmental conditions and culture medium composition are known to alter microalgae biochemical structure possibly affecting the type and concentrations of bioactive compounds with antimicrobial properties. In this work, solvent extracts of the microalgae Chlorella spp. were tested for antimicrobial effects against gram-positive and multidrug resistant pathogenic bacteria Staphylococcus hyicus, Enterococcus faecalis and Streptococcus suis. Microalgae was cultivated at field scale open pond reactor using raw swine wastewater as growth substrate. Dichloromethane or methanol were used to obtain the microalgae extracts. Characterization of the extracts by ultra-high performance liquid chromatography-quadrupole mass spectrometry revealed the presence of 23 phytochemicals with recognized antimicrobial properties. Bacteriostatic activity was observed in plating assays by formation of inhibition zones ranging from 7 to 18 mm in diameter. Only dichloromethane extracts were inhibitory to all three model bacteria. The minimum inhibitory concentration assessed for dichloromethane extracts were 0.5 mg mL^-1 for Staphylococcus hyicus and Enterococcus faecalis and 0.2 mg mL^-1 for Streptococcus suis. Bactericidal effects were not observed using solvent-extracts at 2 or 5 mg L^-1. To the best of authors knowledge, this is the first report on the antimicrobial effects of Chlorella spp. extracts against Staphylococcus hyicus and Streptococcus suis. Overall, Chlorella spp. grown on swine wastewater contains several phytochemicals that could be further explored for the treatment of infections caused by antibiotic-resistant bacteria pathogens.

Seaweeds as a “Palatable” Challenge between Innovation and Sustainability: A Systematic Review of Food Safety

Moderate or severe food insecurity affect 2 billion people worldwide. The four pillars of food security (availability, access, use and stability) are in danger due to the impact of climatic and anthropogenic factors which impact on the food system. Novel foods, like seaweeds, have the potential to increase food yields so that to contribute in preventing or avoiding future global food shortages. The purpose of this systematic review was to assess microbiological, chemical, physical, and allergenic risks associated with seaweed consumption. Four research strings have been used to search for these risks. Preferred Reporting Item for Systematic Reviews and Meta-analysis (PRISMA) guidelines were applied. Finally, 39 articles met the selected criteria. No significant hazards for microbiological, allergenic, and physical risks were detected. Regarding chemical risk, algae can accumulate various heavy metals, especially when harvested in polluted sites. Cultivating seaweeds in a controlled environment allows to avoid this risk. Periodic checks will be necessary on the finished products to monitor heavy metals levels. Since the consumption of algae seems to be on the rise everywhere, it seems to be urgent that food control authorities establish the safety levels to which eating algae does not represent any risk for human health.

Application of Green Algal Planktochlorella nurekis Biomasses to Modulate Growth of Selected Microbial Species

As microalgae are producers of proteins, lipids, polysaccharides, pigments, vitamins and unique secondary metabolites, microalgal biotechnology has gained attention in recent decades. Microalgae can be used for biomass production and to obtain biotechnologically important products. Here, we present the application of a method of producing a natural, biologically active composite obtained from unicellular microalgae of the genus Planktochlorella sp. as a modulator of the growth of microorganisms that can be used in the cosmetics and pharmaceutical industries by exploiting the phenomenon of photo-reprogramming of metabolism. The combination of red and blue light allows the collection of biomass with unique biochemical profiles, especially fatty acid composition (Patent Application P.429620). The ethanolic and water extracts of algae biomass inhibited the growth of a number of pathogenic bacteria, namely Enterococcus faecalis, Staphylococcus aureus PCM 458, Streptococcus pyogenes PCM 2318, Pseudomonas aeruginosa, Escherichia coli PCM 2209 and Candida albicans ATCC 14053. The algal biocomposite obtained according to our procedure can be used also as a prebiotic supplement. The presented technology may allow the limitation of the use of antibiotics and environmentally harmful chemicals commonly used in preparations against Enterococcus faecalis, Staphylococcus aureus, Streptococcus pyogenes, Pseudomonas aeruginosa, Escherichia coli or Candida spp.

Alimentary and Pharmaceutical Approach to Natural Antimicrobials against Clostridioides difficile Gastrointestinal Infection

Incidence of Clostridioides difficile infection (CDI) has been increasing in recent decades due to different factors, namely (i) extended use of broad-spectrum antibiotics, (ii) transmission within asymptomatic and susceptible patients, and (iii) unbalanced gastrointestinal microbiome and collateral diseases that favor C. difficile gastrointestinal domination and toxin production. Although antibiotic therapies have resulted in successful control of CDI in the last 20 years, the development of novel strategies is urged in order to combat the capability of C. difficile to generate and acquire resistance to conventional treatments and its consequent proliferation. In this regard, vegetable and marine bioactives have emerged as alternative and effective molecules to fight against this concerning pathogen. The present review examines the effectiveness of natural antimicrobials from vegetable and algae origin that have been used experimentally in in vitro and in vivo settings to prevent and combat CDI. The aim of the present work is to contribute to accurately describe the prospective use of emerging antimicrobials as future nutraceuticals and preventive therapies, namely (i) as dietary supplement to prevent CDI and reduce CDI recurrence by means of microbiota modulation and (ii) administering them complementarily to other treatments requiring antibiotics to prevent C. difficile gut invasion and infection progression.

Antimicrobials from Seaweeds for Food Applications

The exponential growth of emerging multidrug-resistant microorganisms, including foodborne pathogens affecting the shelf-life and quality of foods, has recently increased the needs of the food industry to search for novel, natural and eco-friendly antimicrobial agents. Macroalgae are a bio-diverse group distributed worldwide, known to produce multiple compounds of diverse chemical nature, different to those produced by terrestrial plants. These novel compounds have shown promising health benefits when incorporated into foods, including antimicrobial properties. This review aims to provide an overview of the general methods and novel compounds with antimicrobial properties recently isolated and characterized from macroalgae, emphasizing the molecular pathways of their antimicrobial mechanisms of action. The current scientific evidence on the use of macroalgae or macroalgal extracts to increase the shelf-life of foods and prevent the development of foodborne pathogens in real food products and their influence on the sensory attributes of multiple foods (i.e., meat, dairy, beverages, fish and bakery products) will also be discussed, together with the main challenges and future trends of the use of marine natural products as antimicrobials.

A Fusion Parameter Method for Classifying Freshness of Fish Based on Electrochemical Impedance Spectroscopy

Compared with using a single characteristic parameter of electrochemical impedance spectroscopy (EIS) to classify the freshness of fish samples from different origins, more characteristic parameters could bring higher accuracy as well as complexity, subjectivity, and uncertainty. In order to eliminate the disadvantages of the multiparameter model, a data fusion method based on model similarity (DFMS) was proposed in this study. The similarity relation between the freshness models based on EIS characteristic parameters and physicochemical indicator was analyzed and quantified accordingly, and then, the weighting factors of the fusion model were determined. The classification accuracy rate of fish freshness based on DFMS was 9.2∼15% greater than that of a single EIS characteristic parameter. The novel dimensionless fusion parameter method proposed in this article might provide a simple yet effective indicator for EIS-based food quality evaluation.

Microalgae n-3 PUFAs Production and Use in Food and Feed Industries

N-3 polyunsaturated fatty acids (n-3 PUFAs), and especially eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), are essential compounds for human health. They have been proven to act positively on a panel of diseases and have interesting anti-oxidative, anti-inflammatory or anti-cancer properties. For these reasons, they are receiving more and more attention in recent years, especially future food or feed development. EPA and DHA come mainly from marine sources like fish or seaweed. Unfortunately, due to global warming, these compounds are becoming scarce for humans because of overfishing and stock reduction. Although increasing in recent years, aquaculture appears insufficient to meet the increasing requirements of these healthy molecules for humans. One alternative resides in the cultivation of microalgae, the initial producers of EPA and DHA. They are also rich in biochemicals with interesting properties. After defining macro and microalgae, this review synthesizes the current knowledge on n-3 PUFAs regarding health benefits and the challenges surrounding their supply within the environmental context. Microalgae n-3 PUFA production is examined and its synthesis pathways are discussed. Finally, the use of EPA and DHA in food and feed is investigated. This work aims to define better the issues surrounding n-3 PUFA production and supply and the potential of microalgae as a sustainable source of compounds to enhance the food and feed of the future.

Seaweed-Based Compounds and Products for Sustainable Protection against Plant Pathogens

Sustainable agricultural practices increasingly demand novel, environmentally friendly compounds which induce plant immunity against pathogens. Stimulating plant immunity using seaweed extracts is a highly viable strategy, as these formulations contain many bio-elicitors (phyco-elicitors) which can significantly boost natural plant immunity. Certain bioactive elicitors present in a multitude of extracts of seaweeds (both commercially available and bench-scale laboratory formulations) activate pathogen-associated molecular patterns (PAMPs) due to their structural similarity (i.e., analogous structure) with pathogen-derived molecules. This is achieved via the priming and/or elicitation of the defense responses of the induced systemic resistance (ISR) and systemic acquired resistance (SAR) pathways. Knowledge accumulated over the past few decades is reviewed here, aiming to explain why certain seaweed-derived bioactives have such tremendous potential to elicit plant defense responses with considerable economic significance, particularly with increasing biotic stress impacts due to climate change and the concomitant move to sustainable agriculture and away from synthetic chemistry and environmental damage. Various extracts of seaweeds display remarkably different modes of action(s) which can manipulate the plant defense responses when applied. This review focuses on both the similarities and differences amongst the modes of actions of several different seaweed extracts, as well as their individual components. Novel biotechnological approaches for the development of new commercial products for crop protection, in a sustainable manner, are also suggested.

Extraction, Properties, and Applications of Bioactive Compounds Obtained from Microalgae

With the increase in the global population, getting new sources of food is essential. One of the solutions can be found in the oceans due to algae. Microalgae are aquatic photosynthetic organisms used mainly due to their variety of bioactive compounds. The consumption of microalgae has been carried out for centuries and is recommended by organizations, such as OMS and FAO, due to its nutritional value and its properties. Based on the existing literature, there is substantial evidence of the nutritional quality of the algae as well as their functional elements. However, much quantification is still necessary, as well as studying possible adverse effects. The present review describes the compounds of alimentary interest present in these algae as well as different extraction techniques assisted by different energetic mechanisms (such as heat, supercritical-fluid, microwave, ultrasound, enzymes, electric field, high hydrostatic pressure, among others). The most challenging and crucial issues are reducing microalgae growth cost and optimizing extraction techniques. This review aimed a better understanding of the uses of microalgae for new researches in nutrition. Since the use of microalgae is still a field in which there is much to discover, it is likely that more benefits will be found in its consumption.

Natural bioactive substances for the control of food-borne viruses and contaminants in food

Abstract

Food-borne viruses and contaminants, as an important global food safety problem, are caused by chemical, microbiological, zoonotic, and other risk factors that represent a health hazard. Natural bioactive substances, originating from plants, animals, or microorganisms, might offer the possibility of preventing and controlling food-borne diseases. In this contribution, the common bioactive substances such as polyphenols, essential oils, proteins, and polysaccharides which are effective in the prevention and treatment of food-borne viruses and contaminants are discussed. Meanwhile, the preventive effects of natural bioactive substances and the possible mechanisms involved in food protection are discussed and detailed. The application and potential effects of natural bioactive substances in the adjuvant treatment for food-borne diseases is also described.

Graphical abstract

Edible Seaweeds and Spirulina Extracts for Food Application: In Vitro and In Situ Evaluation of Antimicrobial Activity towards Foodborne Pathogenic Bacteria

Research is more and more focused on studying and selecting food preservatives of natural origin. In this scenario, algae are an excellent source of bioactive compounds, among which are antimicrobials, whose presence is variable depending on the algal species and environmental conditions. The aim of the present study was to obtain, by a food grade approach, antimicrobial extracts from five species already approved as foods and to test their efficacy in vitro (agar well diffusion assay) and in situ (microbial challenge test) towards foodborne pathogenic bacteria. Moreover, the total phenolic compounds of the extracts were determined in order to evaluate possible correlations with the antimicrobial activity. Strains belonging to Salmonella spp., Listeria monocytogenes, Escherichia coli, Staphylococcus aureus, and Bacillus cereus were considered. Overall, the extracts showed a good antimicrobial activity in vitro towards all the tested microorganisms, especially L. monocytogenes (15 mm of inhibition diameter). The effect of inhibition was monitored during 24, 48 and 120 h showing a good persistence in time. Arthrospira platensis exerted the highest efficacy, further revealed towards L. monocytogenes on salmon tartare as bacteriostatic using 0.45% of the extract and bactericidal using 0.90%. The presence of phenolic compounds could be related to the antimicrobial activity but was not revealed as the main component of this activity. The extract with the highest phenolic content (18.79 ± 1.90 mg GAE/g) was obtained from Himanthalia elongata. The efficacy, confirmed also in a food matrix, might open perspectives for their application as food preservative.

Macroalgae-A Sustainable Source of Chemical Compounds with Biological Activities

Nowadays, one of the most important research directions that concerns the scientific world is to exploit the earth's resources in a sustainable way. Considering the increasing interest in finding new sources of bioactive molecules and functional products, many research studies focused their interest on demonstrating the sustainability of exploiting marine macroalgal biomass as feedstock for wastewater treatment and natural fertilizer, conversion into green biofuels, active ingredients in pharmaceutical and nutraceutical products, or even for the production of functional ingredients and integration in the human food chain. The objective of the present paper was to provide an overview on the recent progress in the exploitation of different macroalgae species as a source of bioactive compounds, mainly emphasizing the latter published data regarding their potential bioactivities, health benefits, and industrial applications.

Macroalgae as a Source of Valuable Antimicrobial Compounds: Extraction and Applications

In the last few decades, attention on new natural antimicrobial compounds has arisen due to a change in consumer preferences and the increase in the number of resistant microorganisms. Macroalgae play a special role in the pursuit of new active molecules as they have been traditionally consumed and are known for their chemical and nutritional composition and their biological properties, including antimicrobial activity. Among the bioactive molecules of algae, proteins and peptides, polysaccharides, polyphenols, polyunsaturated fatty acids and pigments can be highlighted. However, for the complete obtaining and incorporation of these molecules, it is essential to achieve easy, profitable and sustainable recovery of these compounds. For this purpose, novel liquid-liquid and solid-liquid extraction techniques have been studied, such as supercritical, ultrasound, microwave, enzymatic, high pressure, accelerated solvent and intensity pulsed electric fields extraction techniques. Moreover, different applications have been proposed for these compounds, such as preservatives in the food or cosmetic industries, as antibiotics in the pharmaceutical industry, as antibiofilm, antifouling, coating in active packaging, prebiotics or in nanoparticles. This review presents the main antimicrobial potential of macroalgae, their specific bioactive compounds and novel green extraction technologies to efficiently extract them, with emphasis on the antibacterial and antifungal data and their applications.

Exploiting the use of agro-industrial residues from fruit and vegetables as alternative microalgae culture medium

There is a need for searching new microalgae species, and the most suitable strategy to increase the cost-effectiveness of a microalgae culture system is to use resources of low costs, such as residues. This study aimed to evaluate the cultivation of microalgae isolated from the Brazilian Northeast region (Lagerheimia longiseta, Monoraphidium contortum, and Scenedesmus quadricauda) in an alternative medium of low cost (biocompost of discarded fruits and vegetables) with a view to possible applications in the food industry. Microalgae cultivated in the conventional synthetic medium was used as control. The cultivation of microalgae in the alternative medium allowed suitable cell growth, and improved the antioxidant activity and the levels of monounsaturated fatty acid and polyunsaturated fatty acid compared to the synthetic medium. The cultivation of S. quadricauda and L. longiseta species in the alternative medium resulted in increased protein content and/or total phenolic content, and improved health indices (lower levels of atherogenic, thrombogenic, and hypercholesterolemic saturated fatty acids indices, and higher levels of desired fatty acids index) compared to cultivation in synthetic medium. The cultivation of M. contortum in the alternative medium contributed to the production of higher lipid content, mainly saturated fatty acid (palmitic acid), which contributed negatively to the health indices. This study proved that S. quadricauda and L. longiseta microalga species from freshwaters have significant potential for distinct applications in functional food industries, and the biocompost of discarded fruits and vegetables is a suitable medium for microalgae cultivation.

Edible Coating and Pulsed Light to Increase the Shelf Life of Food Products

The application of edible coatings (EC) in combination with pulsed light (PL) treatments represents an emerging approach for extending the shelf life of highly perishable but high value-added products, such as fresh-cut fruits and vegetables. The surface of these products would benefit from the protective effects of ECs and the PL decontamination capability. This review describes in detail the fundamentals of both EC and PL, focusing on the food engineering principles in the formulation and application of EC and the delivery of efficient PL treatments and the technological aspects related to the food characterization following these treatments and discussing the implementation of the two technologies, individually or in combination. The advantages of the combination of EC and PL are extensively discussed emphasizing the potential benefits that may be derived from their combination when preserving perishable foods. The downsides of combining EC and PL are also presented, with specific reference to the potential EC degradation when exposed to PL treatments and the screening effect of PL transmittance through the coating layer. Finally, the potential applications of the combined treatments to food products are highlighted, comparatively presenting the treatment conditions and the product shelf-life improvement.