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BACKGROUND: This study investigated the feasibility of producing pigments from Scenedesmus dimorphus using different lowcost synthetic and alternative media. Thus the influence of nitrogen and phosphorus deficiency, different nitrogen sources and alternative culture media (wheat bran, garlic powder, wheat bran supplemented with garlic powder) on pigment and biomass production was evaluated. RESULTS: Among the three sources of nitrogen studied (ammonium sulfate, urea and sodium nitrate), urea was the cheapest efficient alternative source of nitrogen for pigment production, especially total chlorophylls (67.38 ∼g L −1 d −1 ), by this strain, without strongly affecting biomass yield. Phosphorus deficiency had no negative effect on biomass production, but improved the production of zeaxanthin and chlorophyll b by13.1% and 26.8%, respectively, compared to control. Compared to BG-11 medium, the alternative garlic powder medium increased the biomass yield of S. dimorphus by 5.2 times, improved the productivity of xanthophylls and contributed to the accumulation of ⊎-carotene. Wheat bran medium was found to be efficient as a zero-cost culture medium for the production of pigments, where S. dimorphus accumulated twice the total pigment concentration of the control, with high ⊎-carotene productivity (38.58 ± 11.94 ∼g L −1 d −1 ). The addition of garlic powder to wheat bran increased the biomass (3.14 g L −1 ) and pigment productivity (216.86 ± 2.06 ∼g L −1 d −1 ) by 28.5 and 1.4 times, respectively, but inhibited zeaxanthin biosynthesis. This alternative medium reduced biomass and pigment production costs by 99.80% and 96.21%, respectively. CONCLUSION: Wheat bran supplemented with garlic powder showed good application potential for the industrial production of biomass and pigments from S. dimorphus in open cultivation systems where garlic powder might be used simultaneously for biomass and pigment accumulation, and for biological contamination control.

The microalgae treatment system is economically and environmentally friendly option of wastewater treatment. However, the effects of heavy metals toxicity on microalgae cells could limit the use of microalgae in the treatment of industrial effluents rich in heavy metals. In the current work, we studied the effect of Ni, Cu, Al, Hg and Pb, added as single metal solutions to the microalgae culture medium, on the growth of twenty indigenous strains belonging to a wide variety of microalgae genera. Ni and Cu metals were the most toxic to the tested strains. A high tolerant strain of the Phacus genera was selected. We determined the effect of multiple combinations of Ni, Al and Pb on the cell growth of the selected strain and on the removal capacity of each metal from the microalgae culture medium. Phacus was able to grow in the multi metal solution (Ni, 5.00 mg/L; Al, 9.94 mg/L and Pb 1.00 mg/L) and to efficiently remove the metals with removal capacity of 8.82 ±0.16 mg/g for Ni, 2.09 ± 0.05 mg/g for Pb and 16.90 ± 0.53 mg/g for Al. The reductions of Ni, Al and Pb concentrations in the media were 66.67, 64.28 and 79.17% respectively.