Ines Dahmen-Ben Moussa

Petroleum refinery stripped wastewater (SWW) is characterized by high concentrations of organic matter, hydrocarbons, and polyphenols, making its treatment challenging. Microalgae and microalgae-bacteria consortia represent sustainable alternatives to conventional physicochemical approaches, offering the combined benefits of pollutant removal and biofuel feedstock generation. In this study, the capacity of Picocystis sp. (Pico) alone and in consortium with aerobic bacteria (Pico-Bac) to remediate SWW was assessed in 2-L photobioreactors. Both systems supported algal growth in 10% and 25% SWW, with enhanced chlorophyll a content relative to controls. Notably, lipid accumulation in Picocystis biomass reached 55 mg/g dry weight after six days in 25% SWW, compared with only 9.5 mg/g in the control. Pollutant removal efficiency varied with treatment: Pico-Bac achieved maximum COD and polyphenol reductions of 72% and 96.4%, respectively, at 10% SWW, while hydrocarbon removal was highest (80.4%) at 25% SWW. In contrast, the greatest oil and grease removal (62.2%) occurred in the Pico monoculture at 25% SWW. Phytotoxicity assays of lipid- using Lepidium sativum seeds confirmed detoxification, as treated 25% SWW not only supported germination but also stimulated root elongation. To the best of our knowledge, this study provides the first evidence of the combined application of Picocystis sp. and an activated sludge bacterial consortium sourced from a municipal wastewater treatment plant for the remediation of refinery stripped wastewater (SWW). The results highlight a dual advantage: efficient pollutant reduction and production rich biomass, underscoring the potential of this eco-biotechnological process as an innovative route for sustainable wastewater management and biodiesel production.

With the demand for bioproducts that can provide benefits for biotechnology sectors like pharmaceuticals, nutraceuticals, and cosmeceuticals, the exploration of microalgal products has turned toward extremophiles. This chapter is intended to provide an insight to most important molecules from halotolerant species, the cyanobacteria Phormidium versicolor NCC-466 and Dunaliella sp. CTM20028 isolated from Sfax Solar Saltern (Sfax) and Chott El-Djerid (Tozeur), Tunisia. These microalgae have been cultured in standard medium with a salinity of 80 PSU. The in vitro antioxidant activities demonstrated that extremolyte from Dunaliella and Phormidium as, phycocaynin, lipids, and polyphenol compound presents an important antioxidant potential.

BACKGROUND: The three‐phase extraction process of olive oil produces highly contaminated wastewater (OMW). The elimination of this toxic by‐product is an important environmental issue that requires the development of an appropriate management solution. The cultivation of microalgae using OMW as growth medium was therefore studied using single (the culture medium was formed by 0% to 80% ultrafiltered olive mill wastewater (OMUF) or OMW added to BG11) and two‐stage strategies (microalgae were firstly cultivated in the BG11 medium. In the second stage, 40% and 80% of OMUF and OMW were added to the culture). In this work, biodegradation of OMW and subsequent extraction of lipid and antioxidant molecules was investigated as an ecofriendly method for the bioremediation and valorization of OMW.RESULTS: For two‐stage cultivation, OMUF and OMW stress enhanced the intracellular amount of polyphenol accumulated in Scenedesmus sp. and exhibited the highest 2, 2‐diphenyl−1‐ picrylhydrazyl radical (DPPH) and 2,2'‐azino‐bis (3‐ethylbenzoline‐6‐sulfonate) radical (ABTS) scavenging ability compared with single‐stage cultivation. Moreover, the lipid profile is dominated by polyunsaturated acids. In the single‐stage cultivation, the Ch a, Ch b, carotenoid, carbohydrate and lipid content of 2.57, 7.4, 1.69, 368, and 644 g kg⁻¹ were observed in 40% OMUF added culture, respectively, along with high biomass productivity and 58% of polyphenol removal. Moreover, the 3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide (MTT) assay showed that the biomass of Scenedesmus sp. cultured on 40% OMUF did not show any toxic effect, making it an efficient strategy.CONCLUSION: The results indicate that Scenedesmus sp. is a promising microalga for the biotreatment of OMW and the extraction of bioactive metabolites. © 2021 Society of Chemical Industry.

The authors have withdrawn this preprint due to author disagreement.