Foodborne pathogens are one of the important biological hazards causing food spoilage. Nowadays, both research and industry are looking for natural sources of food preservatives and nutraceutical agents as an alternative of the chemical ones. Algae are one of these resources and they exist abundantly in the Egyptian aquatic environment. The algal biomass of Microcystis aeruginosa was used in the present study. Different solvents (deionized water, methanol, ethanol, acetone, chloroform, diethyl ether, ethyl acetate and hexane) were used for extraction the bioactive metabolites from M. aeruginosa. Diethyl ether extract (DEE) showed marked antibacterial activity against all tested foodborne pathogenic bacteria achieving inhibition ranged between 13.3 mm with K. pneumoniae and 29.3 mm with P. aeruginosa. The DEE extract of M. aeruginosa was fractionated using column chromatography technique. Among all fractions of diethyl ether extract, F7 had an effect against all tested bacteria. Eight compounds (9,12-Octadecadienoic acid methyl ester, Hexadecadienoic acid methyl ester, 9-Octadecadienoic acid, Nonadecane, Hexadecane, 9,12,15-Octadecadienoic acid, Octasiloxane and 10-Octadecenoic acid, methyl ester) were identified using GC/MS in such fraction. In addition to the antibacterial activity of DEE and F7, they worked as anticancer agents. Low concentration of DEE (<100 μg ml-1) was required at IC50 for liver, colon and breast cancer cell lines. Fraction F7 had obvious effect against colon cancer cell line with low IC50, 28.73 μg ml-1. Generally, M. aeruginosa had valuable bioactive metabolites which can be used as natural preservatives and anticancer agents.
thus allowing the re-use of wastewater for the irrigation of plants that produce abundant bio-oils and for the irrigation of low-quality soils. Chlorella vulgaris was grown in Om El-Resh drain water as growth medium, after enrichment with nitrogen and phosphorous. Castor seeds were cultivated in a greenhouse at the Algal Biotechnology Unit, National Research Centre, Egypt. Fifteen days later, transplants were irrigated by untreated wastewater (WW); wastewater treated with microalgae (WW+A); or wastewater treated with microalgae followed by removal of microalgae (WW-A). Oil extraction was performed by seed warming and grinding with n-hexane, followed by soaking, filtration, and passage through Silica gel 60. Esterification was performed, and then fatty acid methyl esters (FAMEs) were determined. The results indicated that the wastewater treatment markedly affected seed oil content. The WW+A treatment led to the highest seed oil yield (41.8%), followed WW-A treatment (28.14%), and the WW treatment (25.12%). FAME analysis indicated that the presented fatty acids of castor oil were C16 and C18 and ricinoleic acid (C18:1) was the most abundant (83.1 to 84.63%). In spite of the higher seed oil content when plants were grown in WW+A, there were differences in the fuel proprieties of seed oils in the different groups, based on American Society for Testing and Materials criteria. Our results suggest that wastewater can be successfully used for irrigation of soils that have poor fertility to produce bio-oils during land reclamation.
The effect of mineral nutrition on growth-related metabolites and pigmentation of the filamentous Anabaena flos-aquae and Calothrix sp. PCC7601 was investigated. Key nutrients (iron, phosphorus and nitrogen) were supplied at different concentrations compared to original BG-11 growth medium. The results showed general increase of peptide nitrogen and total sugars, chlorophyll a content and phycobiliprotein pigments content with the use of double concentration of different key nutrients. The opposite was observed for most of these parameters under half and quarter the concentration of nutrients tested in both isolates. Meanwhile, carotenoids increased under half the concentration of iron and phosphorus compared to the original concentrations of BG-11 medium but decreased at quarter concentrations of the original BG-11 medium. The effect of nitrogen limitation on growth and pigments content on A. flos-aquae was overly less severe due to the ability of A. flos-aquae to compensate for limited supply of available nitrogen through nitrogen fixation. At all reduced concentrations of key nutrients, phycoerythrin pigment predominated other phycobiliprotein pigments under white light in Calothrix sp. To further investigate the effect of mineral nutrition and light quality on phycobiliprotein pigment composition, both isolates were grown under green and red monochromatic light. The highest content of phycroerythrin pigment was recorded under green light in both isolates under different nutrients treatments. Phycocyanin, on the other hand, predominated other phycobiliprotein pigments in most of nutrients treatments placed under red light in Calothrix sp. This strain was more responsive in terms of alternating its phycobiliprotein composition than A. flos aquae in response to different nutrients concentration and change in light quality. Thus, this isolate seems to be a promising source for those pigments production. The study shows that growth manipulation using different nutrients concentrations and light qualities can result in differential expression of the phycobiliprotein pigments in some cyanobacterial strains. This can be used for mass production of these valuable pigments for biotechnological applications. Nermin Adel El Semary et al.
Four different solvents were used to study their efficiency on pigments extraction from three different algal species of Chlorella vulgaris, Spirulina platensis and Nannochloropsis oculata. Dimethylsulfoxide, acetone, ethanol and methanol were used in the extraction process. The experiment was performed in both of fresh and oven dried algal samples. Chlorophylls a, b, total chlorophyll and total carotene concentrations were determined spectrophotometrically and by HPLC technique. The spectrophotometric method revealed that, dimethylsulfoxide surpasses all other used solvents in all species and all pigments in fresh samples except for chlorophyll a of N. oculata, whereas acetone was more effective than the others in fresh and dry sample. For the dried sample of C. vulgaris, methanol gave the maximum extractability with chlorophyll a while chlorophyll b and total chlorophyll were found be maximum in dimethylsulfoxide solvent. In Spirulina, methanol represented the maximum chlorophyll a and total chlorophyll for the dried samples. Total carotene was found to be higher in ethanol solvent with both C. vulgaris and N. oculata but dimethylsulfoxide surpasses the other solvents with S. platensis. HPLC results emphasized that, acetone surpasses all other used solvent in fresh samples and methanol was ideal solvent in dry samples of C. vulgaris. Dimethylsulfoxide represented the maximum chlorophyll a and total carotene with Spirulina in both samples. Methanol was the best solvent for extraction of all pigments with N. oculata except with β-carotene of dry sample, ethanol was the best solvent.
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