A Study on the Antimicrobial Activity of Algae Extract: The Fucales Order Case †

: Over the years, foodborne pathogens have caused countess health problems and massive financial losses. Therefore, an essential goal for the food industry is to prevent food contamination and the related foodborne illnesses as microbial contamination of food items during their acquiring and distribution processes is still a hygienic issue. Moreover, there is an important movement leading to the pursuit of more natural and safe food supplies and ingredients with a special emphasis on the vegan and vegetarian community; as a result, there has been a resurgence in demand for natural and eco-friendly products as a replacement for synthetic ingredients. In this context, and due to their active substances, macroalgae stand out as they are known for possessing antibacterial qualities among other abilities. Because of this, the current study updates our understanding of microbial pollutants in the food industry and compiles the latest updates on the scientific reports on antimicrobial activity of the edible brown algae species with special attention to the algae Bifurcaria bifurcata , Fucus spiralis, and Ascophyllum nodosum . These species which belong to the Phaeophyceae class and order Fucales are reportedly rich in active compounds and are still an undervalued resource. So, the ability of algal extracts to stop the growth of various significant food pathogens is reviewed herein, while considering their advantageous effects on food safety and quality issues.


Introduction
Rich in biodiversity, the oceans have gained global importance and are increasingly under scrutiny as a source of natural products.Among the many organisms living in marine habitats, macroalgae have attracted much interest due to their diversity and potent bioactive metabolites [1].Members of the Fucales family, a particular group of brown macroalgae, are known for their ecological importance, metabolite composition, and potent bioactive properties.
These metabolites, ranging from polysaccharides [2] to phenolic compounds [3] and terpenoids [4], not only contribute to the ecological interactions of the algae but also possess promising bioactive properties.This work focuses on exploring the antimicrobial potential of extracts from macroalgae belonging to the Fucales family, namely Bifurcaria bifurcata, Fucus spiralis, and Ascophyllum nodosum.Figure 1 presents photographs of this species in detail and in their natural environment.The study aims to elucidate the spectrum of antimicrobial activity of these extracts against a range of significant microorganisms, highlighting food-related pathogens.
of antimicrobial activity of these extracts against a range of significant microorganisms, highlighting food-related pathogens.

Discussion
With the aim of evaluating the latest published developments in the field of antimicrobial capacity of algal extracts, available databases were searched using the name of the alga and antimicrobial activity as keywords.A summary of the main results published in the last five years is presented in Table 1.
Several important foodborne microorganisms can cause various diseases when ingested through contaminated food.Some of the most important of these are: Salmonella, Escherichia coli, Listeria monocytogenes, and Staphylococcus aureus [5].Macroalgal extracts could play a role as inhibitors of these pathogens [6,7].For example, the pathogenic effect of toxins produced by E. coli is one of the most important causes of foodborne illness worldwide [7,8].Moreover, there are studies also supporting the inclusion of alga extracts as food preserves [9,10].
The antimicrobial activity of B. bifurcaria extracts obtained by maceration with solvents of different polarity has been studied previously.The results highlighted the potential of B. bifurcaria as an effective antimicrobial agent, as all extracts were active against five of the six microorganisms tested [11].In another work, the algal extract (hexane-isopropanol-water (10:80:10)) was tested against Bacillus cereus, Bacillus subtilis, Geobacillus stearothermophilus, L. monocytogenes, S. aureus, and Staphylococcus haemolyticus.The results

Discussion
With the aim of evaluating the latest published developments in the field of antimicrobial capacity of algal extracts, available databases were searched using the name of the alga and antimicrobial activity as keywords.A summary of the main results published in the last five years is presented in Table 1.
Several important foodborne microorganisms can cause various diseases when ingested through contaminated food.Some of the most important of these are: Salmonella, Escherichia coli, Listeria monocytogenes, and Staphylococcus aureus [5].Macroalgal extracts could play a role as inhibitors of these pathogens [6,7].For example, the pathogenic effect of toxins produced by E. coli is one of the most important causes of foodborne illness worldwide [7,8].Moreover, there are studies also supporting the inclusion of alga extracts as food preserves [9,10].
This antifungal activity was also confirmed by studies conducted with methanolic extracts against P. digitatum and Botrytis cinerea [15].In another study [14], the activity of methanolic extract was used in interrupting the growth of dermatophytic fungi.The authors concluded that the algal alga has an important inhibitory activity for the action on Epidermophyton floccosum and is one of the most effective algae in the published literature.In addition, the preservative effect of B. bifurcata extracts was tested on the quality of chilled hake quality shake.The results highlight the antimicrobial effect of aqueous and ethanolic B. bifurcata extracts in the icing media and demonstrate the potential of macroalgae bioactive compounds to preserve food quality [9].
Similarly, extracts of Fucus spiralis have been tested as antimicrobial and antifungal agents.A study on the antifungal activity of the methanolic extract of F. Spiralis against P. digitatum and Botrytis cinerea [15] showed a moderate effect but pointed out the seasonal variation of this property, since only the extracts from the alga harvested in summer were active.Inhibition of various Gram-positive and Gram-negative microorganisms has been described by N. Grozdanic et al.The most active antibacterial effect was achieved by the n-butanol fraction, with Mics values ranging from 0.04 mg/mL for B. cereus and B. subtilis to 0.14 mg/mL for P. mirabilis and E. coli.In the same study, the effect on the fungi Mucor mucedo, Trichophyton mentagrophytes, Aspergilus niger, C. albicans, and P. italicum was also investigated.In both cases (antimicrobial and antifungal activity), the lipid fraction was the most active [17].This results agree with previous work stating the inhibition of several fungi by phlorotannis from F. spirailis [19].The activity of F. spiralis extracts prepared by heat-assisted extraction with solvents of different polarity was assessed as solvent properties are an important factor in antimicrobial activity [22].The results showed that the most active extract was obtained when acetone was used as a solvent, which was active against S. aureus, B. cereus, and Salmonella enteritidis [11].The antimicrobial activity of F. spiralis extracts was also confirmed by results obtained with dichloromethane/methanol as an extracting solvent, which showed minimal inhibitory concentrations ranging from 2.7 ug/mL (S. aureus) to 1875 ug/mL (E.coli).Among other possibilities, F. spiralis extracts can be used for dermo-cosmetic applications, as they can contribute to the maintenance of a healthy skin microbiota [18].
The antimicrobial capacity of Ascophyllum nodosum was studied in vitro against E. coli serotype O138.The results show a dose-dependent relationship between the inhibitory activity and the concentration of the extract [20]; these results agree with those of Dell'Anno et al., who found an antibacterial action against E. coli O138 evidenced by a decrease in bacteria growth after 3 h attained by 0.12% Ascophyllum nodosum extract concentration, demonstrating a dose-dependent inhibitory effect [21].
The antimicrobial efficacy of an acetone-water mixture (7:3, v/v, 2 mL) A. nodosum extract purified phlorotannins against E. coli.O138, Salmonella agona, and Streptococcus suis have been examined before and showed a range of MICs for the different pathogens between 1.56 and 0.78 mg/mL.The authors also examined cell membrane permeability and intracellular adenosine triphosphate (ATP) to establish the inhibitory mechanism.They conclude that phlorotannin extracts dramatically lowered the intracellular ATP levels of all three microorganisms.Importantly, when subjected to the same or higher dosages that have been proven to inhibit bacterial growth (up to 25 mg/mL), the phlorotannin extracts exhibited no negative effects on pig intestinal cells, suggesting that they could be used as an alternative and supplement to antibiotics and zinc in animal diets [6].
In summary, we found that the three species of algae studied in this mini review have significant antimicrobial capacity, although it is worth pointing out that several factors affect their antimicrobial performance, from the extraction technique used to variations in maturation and provenience of the algal material.However, their applicability, e.g., as an aid in food preservation, is strong and is an interesting topic for future research into applied technology.

Figure 1 .
Figure 1.Macroalgae discussed in this work: detailed outlook and in their natural environment.

Figure 1 .
Figure 1.Macroalgae discussed in this work: detailed outlook and in their natural environment.