The present study demonstrates the antibacterial activity of selected brown and green marine algae collected from Saudi Arabia Red Sea and Arabian Gulf. The methanolic and acetone extracts were tested against gram positive, gram negative bacteria and in an attempt to be used as an alternative to commonly used antibiotics. Both brown seaweed species and methanolic extracts were found to be active against gram positive than gram negative; however, acetone extract gave the highest inhibitory activity against sp. On the other hand, organic extract demonstrated higher antibacterial activity than the fresh extract but both extracts revealed decreased activity compared to extracts. methanolic extract showed an obvious effect on methicillin resistant (MRSA). The present work shows a comparable therapeutic potency of the tested seaweed members and extracts in treating human microbial pathogens to synthetic chemical antibiotics. A remarkable higher antioxidant DPPH free radical scavenging effect was recorded with sp. compared to sp. FTIR Infrared Spectrometer analysis together with the high performance liquid chromatography provided a detailed description of the possible functional constituents and the major chemical components present in marine macroalgae particularly in brown seaweeds to be mainly of phenolic nature to which the potent antimicrobial activity is being attributed.

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In this study, initially 11 different bacterial strains were tested for the degradation capabilities against Basic Orange 2 dye. In initial screening with 78.90% degradation activity, Escherichia coli emerged as the most promising strain to degrade the selected dye, and was then employed in subsequent experiments. For further enhancing the degradation capability of selected bacteria, the effects of various physicochemical parameters were also evaluated. Among the tested parameters, 20 ppm dye concentration, 1666 mg/L glucose concentration, a temperature of 40 °C, 666 mg/L sodium chloride concentration, pH 7, 1000 mg/L urea concentration, a 3-day incubation period and the use of sodium benzoate as a redox mediator (666 mg/L) were found to be ideal conditions to get the highest decolorization/degradation activities. Finally, all the mentioned parameters were combined in a single set of experiments, and the decolorization capacity of the bacteria was enhanced to 89.88%. The effect of pH, dye concentration, incubation time and temperature were found to be responsible for the optimum degradation of dye (p < 0.05), as predicted from the ANOVA (analysis of variance) of the response surface methodology. The metabolites were collected after completion of the process and characterized through Fourier transform irradiation (FTIR) and gas chromatography mass spectrometry (GC-MS). From the data obtained, a proposed mechanism was deduced where it was assumed that the azo bond of the dye was broken by the azoreductase enzyme of the bacteria, resulting in the formation of aniline and 3, 4-diaminobezeminium chloride. The aniline was then further converted to benzene by deamination by the action of the bacterial deaminase enzyme. The benzene ring, after subsequent methylation, was transformed into o-xylene, while 3, 4-diaminobezeminium chloride was converted to p-xylene by enzymatic action. These findings suggest that Escherichia coli is a capable strain to be used in the bioremediation of textile effluents containing azo dyes. However, the selected bacterial strain may need to be further investigated for other dyes as well.

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Nowadays, marine microalgae are recognized to be a considerably novel and rich origin of bioactive moieties utilized in the sectors of nutraceuticals and pharmaceuticals. In the present study, Nannochloropsis oculata extract (AME) was associated with a wide variety of pharmacological studies such as in vitro antioxidant, antibacterial, and antifungal and anticancer activity (MDA-MB-231) in cancer cells through in vitro models. In the study, the chemical composition and structure of the bioactive compounds found in the AME extract were studied using the LC-MS technique. The results of the anticancer activity showed a decrease in the percentage of cell viability of the MDA-MB-231 cells in a concentration- and time-dependent manner (400 μg/mL at 24 h, 300 μg/mL at 48 h, and 200 μg/mL at 72 h). We have also observed morphological changes in the cells that could be associated with treatment with AME extract. Our observation of the AME extract-treated MDA-MB231 cells under light microscopy showed that when the concentration increased, the number of cells began to decrease. As far as LC-MS analysis is concerned, it showed the presence of the bioactive molecules was terpenoids along with carotenoids, polyphenolic and fatty acids. The result revealed that the AME extract exhibited noteworthy in vitro free radical scavenging potential, with an IC50 value of 52.10 ± 0.85 µg/L in DPPH assay, 122.84 ± 2.32 µg/mL in H2O2 assay and, 96.95 ± 1.68 µg/mL in ABTS assay. The activity was found to be highly significant against bacteria (Gram-positive and negative) and moderately significant against fungal strain with minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC)/minimum fungicidal concentration (MFC) values between 15.63 and 500 µg/mL.

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