Cold-pressed black cumin seed oil (BCSO) and cumin seed oil (CSO) were evaluated for their fatty acid profiles, phytosterol and tocopherol contents, antiradical properties and inhibition of microbial growth. The main fatty acids in BCSO were linoleic followed by oleic and palmitic acids. Petroselinic acid (C18:1n-12) was the main fatty acid in CSO, while linoleic acid was the second major unsaturated acid. Six sterol compounds were measured in BCSO and CSO, wherein the sterol marker was b-sitosterol. a-Tocopherol constituted 45% of tocopherols in BCSO, while b-tocopherol was the main component in CSO. BCSO and CSO oils had higher antiradical action against DPPHÁ and galvinoxyl radicals than virgin olive oil. Antimicrobial properties of BCSO and CSO were studied, and the results revealed that CSO inhibited the growth of all microorganisms tested, while BCSO inhibited the growth of all microorganisms tested except A. niger and A. flavus. BCSO and CSO had a drastic effect on the biosynthesis of protein and lipids in cells of B. subtilis.

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The goal of the present investigation was to study the effect of pH on growth and biochemical responses of Dunaliella bardawil and Chlorella ellipsoidea when exposed to different pH values. The two tested microalgae could grow in a wide range of pH (4-9 for D. bardawil and 4-10 for C. ellipsoidea). The dry weight gain and the biochemical components of D. bardawil were greatly enhanced at pH 7.5. In contrast, dry weight and carbohydrate content of C. ellipsoidea attained their maximum values at the alkaline pH. On the other hand, the protein content of C. ellipsoidea recorded its highest value at pH 4, while the pigment content of the same alga was highest at pH 4, 6, and 7.5 and decreased at alkaline pH. Both pH 6 and pH 9 stimulated the accumulation of β-carotene, vitamin E and vitamin C in D. bardawil, with the highest values of the three compounds recorded at pH 9. In the case of C. ellipsoidea, β-carotene content increased at pH 6 and pH 10 as compared with the control, but the amount of β-carotene was much higher at pH 6 than at pH 10. Vitamin E content was higher in C. ellipsoidea cells at pH 10 than at pH 6. Both pH 6 and pH 10 caused a significant decline in vitamin C content of C. ellipsoidea.

The compositions and concentrations of lipid classes, fatty acids, tocopherols were determined in the lipids from blue-green microalga Spirulina platensis. Total lipids (TL) recovered using chloroform: methanol (2:1, v/v) were found to be 163.5 g/kg (on dry weight basis). The level of neutral lipids was the highest, followed by glycolipids and phospholipids, respectively. Among TL and lipid classes, palmitic, γ-linolenic and linoleic acids were the dominating fatty acids. Compared to the neutral lipids, the polar fractions were generally characterised by higher percentages of saturated fatty acids. The recovered lipids were characterised by high percentage of tocopherols, wherein α-tocopherol constitutes about 73% of total tocopherols present, the rest being γ-tocopherol. Spirulina platensis lipids exhibited a strong radical scavenging activity towards stable DPPH free radicals, whereas 27% of DPPH radicals were quenched after 2 h incubation. TL and lipid classes inhibited the growth of different microorganisms except gramnegative bacteria. At high concentrations, the tested lipids appeared more effective against a. niger (28.3 ± 1.53 mm). The information obtained in the present investigation is useful for lipid characterisation and further chemical and nutritional investigations of Spirulina platensis.

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