Twenty-three bacterial isolates from polluted water and soil were screened for heavy metals resistance (i.e., Al(3+), Co(2+), and Cu(2+)). The most potent isolate was identified by morphological characteristics, biochemical tests and confirmed by API20E kits as Providencia rettgeri MAM-4. Removal of Al(3+) from aqueous solution by P. rettgeri is more efficient (∼fourfold) than that by B. cereus ATCC 11778 (a comparison strain) at concentration of 200 mg L(-1) Al(3+). P. rettgeri was able to remove Co(2+) more than B. cereus ATCC 11778 at concentration of 50 mg L(-1) Co(2+). Inoculation of P. rettgeri into clay enhanced significantly the removal of Al(3+), Co(2+), and Cu(2+). P. rettegri MI (mutant strain) was able to tolerate more Al(3+) than that of the parent strain. P. rettgeri was resistant to 7 out of 15 antibiotics tested. P. rettgeri MAM-4 isolated from wastewater had ability to remove Al(3+), Co(2+), and Cu(2+) efficiently from aqueous media; and enhanced significantly metal biosporption by clay. This study has revealed that P. rettgeri could be employed as an effective and economic technology for the removal such metal elements from polluted environment.
Ten different microalgal species were screened for their antioxidant activity using 2,2 ́-diphenyl-1-picrylhydrazyl (DPPH) scavenging assay, both total phenolic and carotenoid contents were determined. The ethanolic extract ofOscillatoriasp. showed the highest antioxidant activity (69.1 %), while the greenChlorellasp. showed higher phenolic content (39.1 mg GAE g-1dry wt.) andScenedesmus obliquusrecorded higher carotenoid content (3.73 mg L-1), than cyanobacterial species Microalgal biomass plays a great role as a potential source of natural antioxidants, not only due to the carotenoids but also the phenolic compounds.
The present work investigated the effects of nitrogen (N), phosphorus (P), magnesium (Mg), carbonate (CO 3) concentrations and gamma radiation doses on growth and lipid production of Chlorella vulgaris. The obtained results showed that culture conditions have highly significant effects on biomass and lipid accumulation. The maximum lipid content was observed at 350, 40, 150,20 mg L −1 of N, P, Mg, and CO 3 concentrations, respectively. While the highest biomass yield was achieved at high N and P as well as reduced Mg and CO 3 concentrations. Whereas gamma radiation showed a negative effect. Lipid profile recorded maximum saturated (SFAs, 62.44%) and unsaturated fatty acids (UFAs, 37.56%) with palmitic acid (C16:0), linoleic acid (C18:2), pentadecanoic acid (C15:0), palmitoleic acid (C16:1) and oleic acid (C18:1) as predominant fatty acids, which prove that Chlorella vulgaris is a promising feedstock for biodiesel production.
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