Unveiling the Potential of Algal Extracts as Promising Antibacterial and Antibiofilm Agents against Multidrug-Resistant <i>Pseudomonas aeruginosa</i>: In Vitro and In Silico Studies including Molecular Docking

Multidrug-resistant Pseudomonas aeruginosa poses a global challenge due to its virulence and biofilm-forming ability, leading to persistent infections. This study had a dual focus: first, it aimed to investigate the biofilm activity and antibiotic resistance profiles of Pseudomonas aeruginosa isolates obtained from a fish-rearing farm. Second, it explored the potential of algal extracts as effective antibacterial and antibiofilm agents. The study analyzed 23 isolates of P. aeruginosa from the farm, assessing antibiotic resistance and biofilm formation. The antimicrobial and antibiofilm activities of two algal extracts, Arthrospira platensis (cyanobacteria) acetone extract (AAE) and Polysiphonia scopulorum (Rhodophyta) methanol extract (PME), were tested individually and combined (COE). The effects on biofilm-related gene expression were examined. AAE, PME, and COE were evaluated for antimicrobial and antibiofilm properties. Biofilm-related gene expression was measured and the extracts were analyzed for physicochemical properties and toxicity. Most P. aeruginosa isolates (86.9%) were antibiotic-resistant and formed biofilms. AAE, PME, and COE displayed promising antibacterial and antibiofilm effects, with COE being particularly effective. COE reduced a key biofilm-related gene expression. The fatty acid content (56% in AAE and 34% in PME) correlated with the effects. Specific compounds, such as phytol, bromophenol, and dihydroxy benzaldehyde, contributed to the activities. The extracts showed favorable characteristics and interactions with FabZ protein amino acids. This study suggests the potential of algal extracts as antibacterial and antibiofilm agents against drug-resistant infections. Further exploration in clinical applications is warranted

A novel study on the inhibitory effect of marine macroalgal extracts on hyphal growth and biofilm formation of candidemia isolates

Biofilm formation and hyphal growth are considered to be the most serious virulence factors of Candida species in blood causing candidemia infections, which are difficult to treat due to the spread of resistant Candida isolates to most antifungal drugs. Therefore, in this study, we investigated the effect of different types and concentrations of selected macroalgal extracts from Cladostephus spongiosus (Phaeophyta), Laurencia papillosa (Rhodophyta), and Codium arabicum (Chlorophyta) in inhibiting those virulence factors of the isolated Candida. Acetone extract of C. spongiosus (AECS) showed a stronger anticandidal activity against the selected strains than ethanol extract. Candida krusei was the highest biofilm producer among the selected isolates. AECS showed an inhibition of C. krusei biofilm formation as well as a reduction in the viability of preformed biofilms. Also, AECS reduced various sugars in the candidal exo-polysaccaride layer (EPS). Scanning electron microscopy (SEM) and light microscopic images revealed an absence of hyphae and an alteration in the morphology of biofilm cells when treated with AECS. Moreover, AECS downregulated the expression of hyphal specific genes, hyphal wall protein 1 (HWP1), Agglutinin-like protein 1 (ALS1) and fourth secreted aspartyl proteinase (SAP4), which confirmed the inhibitory effect of AECS on hyphal growth and biofilm formation. Gas chromatography-mass spectrophotometer (GC-MS) analysis of AECS showed three major compounds, which were non-existent in the ethanol extract, and might be responsible for the anticandidal activity; these revealed compounds were 4- hydroxy-4-methyl-2-pentanone, n-hexadecenoic acid, and phenol, 2-methoxy-4-(2- propenyl). These active compounds of AECS may be promising for future pharmaceutical applications in the treatment of candidemia

Application of Plackett–Burman design for the high production of some valuable metabolites in marine alga Nannochloropsis oculata

Microalgae have efficient nutritional influence to obtain high survival growth and quality of fish larvae and to promote the growth of brine shrimp. In this work the Plackett–Burman statistical design was applied to specify which nutrient factor(s) optimize the nutritional contents [protein, carbohydrate, β-carotene, ascorbic acid and free radical scavenging activity (DPPH)] in the marine alga Nannochloropsis oculata used in aquaculture to maximize marine hatchery production. N. oculata was cultured on F/2 medium (as control) to reach its maximum growth. The obtained results showed that the maximum growth, chlorophyll-a,b and carotenoid contents were attained after 10 days. The contents of all studied parameters in N. oculata grown on the optimized medium after10 days increased significantly (P ⩽ 0.1) than those on control with low concentration of PO4 (2.5 g l−1) and with high concentration of NO3 (112.5 g l−1) except for cell numbers and DPPH. Significant increases in the protein, carbohydrate, ascorbic acid, β-carotene and DPPH in Artemia franciscana enriched with N. oculata cultured on the newly optimized medium were observed

Impact of Commercial Seaweed Liquid Extract (TAM®) Biostimulant and Its Bioactive Molecules on Growth and Antioxidant Activities of Hot Pepper (Capsicum annuum)

Bioactive molecules derived from seaweed extracts are revolutionary bio-stimulants used to enhance plant growth and increase yield production. This study evaluated the effectiveness of a commercially available seaweed liquid extract, namely, True-Algae-Max (TAM®), as a plant growth stimulant on nutritional, and antioxidant activity of Capsicum annuum. Three concentrations of TAM® (0.25, 0.5, and 1%) of various NPK: TAM® ratios were investigated via foliar spray, over 2017 and 2018 cultivation seasons, under greenhouse conditions. TAM® is rich in phytochemical compounds, such as ascorbic acid (1.66 mg g−1), phenolics (101.67 mg g−1), and flavonoids (2.60 mg g−1) that showed good antioxidant activity (54.52 mg g−1) and DPPH inhibition of 70.33%. Promoting measured parameter results stated the extensive potentiality of TAM® application, in comparison with conventional NPK treatment. Yield and composition of C. annuum were significantly improved in all TAM® treated groups, especially the TAM0.5% concentration, which resulted in maximum yield (4.23 Kg m−2) and significant amounts of profuse biological molecules like chlorophyll, ascorbic, phenolic compounds, flavonoids, and total nutrients. Compared to the NPK control treatments, C. annuum treated with TAM0.5% improved the total antioxidant activity of hot Pepper from 162.16 to 190.95 mg g−1. These findings indicate that the extract of seaweed can be used as an environmentally friendly, multi-functional biostimulant in the agricultural field for more sustainable production, in addition to reducing the use of hazardous synthetic fertilizers

Commercial Seaweed Liquid Extract as Strawberry Biostimulants and Bioethanol Production

Seaweeds are increasingly intriguing as a sustainable source of bioactive compounds. They have applications in agriculture, fuels, feed, and food products. To become a cost-competitive product with zero waste, a biorefinery approach is applied, where several products are valorized at the same time. True-Algae-Max (TAM®) has been investigated for its ability to improve the yield and nutritional facts of a strawberry plant. Three concentrations of TAM (0, 50, and 100%) were examined by foliar spray in 2017 with 50% NPK chemical fertilizer. Results indicated that growth, yield, chlorophyll, and potassium content were significantly improved by TAM treatments. TAM50 % resulted in maximum root length, leaf area, plant fresh weight, fruit weight, and yield with an increase ranging from 10 to 110% compared to control. Compared to the NPK control, strawberries grown with TAM50% improved total soluble solids (TSS) from 7.58 to 10.12% and anthocyanin from 23.08 to 29.42 mg CGE 100 g−1. Noteworthily, this reduced total sugar, and total phenolics were boosted by TAM applications, while non-reducing sugar was reduced compared to control. On the other hand, whole seaweed biomass and TAM residuals were used for bioethanol production by acid scarification. The maximum bioethanol yield was observed in residual biomass (0.34 g g−1 dw), while the whole seaweed biomass showed only 0.20 g g−1 dw. These results proved the biorefinery concept of using seaweed extract as a biostimulator and bioethanol production