Effect of olive mill wastewaters on Scenedesmus sp. growth, metabolism and polyphenols removal

Abstract

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.

Application of Five Different Chlorella sp. Microalgal Strains for the Treatment of Vegetation Waters Derived from Unconventional Oil Extractions Enriched with Citrus Byproducts

“…According to the recent literature, microalgae belonging to the Scenedesmus sp. genus not only are able to grow on OMWW and remove sugars and phenols [31] but also accumulate polyphenols successfully removed from the WW inside their cells [32]. Hence, we cannot exclude the possibility that the Chlorella sp.…”

Agri-Food Industry Waste as Resource of Chemicals: The Role of Membrane Technology in Their Sustainable Recycling

“…This slurry usually has higher chemical oxygen demand (COD) values [31] in respect to three phase system, thus is more pollutant if disposed of. The traditional used three-phase olive mill production system is a water-intensive process [30] that generated large amounts of dark liquid effluents [27] called olive mill wastewaters (OMWWs) with high electric conductivity (~9.7 −13.8 [31][32][33] mS/cm), a pH value of 4.8-5.6 [31][32][33] and an average composition of 83-92% of water, 4-16% of organic compounds and 1-2% w/w of inorganic salts. OMWWs low pH is attributed to organic acids (such as malonic, citric, tartaric, lactic, fumaric and succinic) that are present.…”

Influence of desalination concentrate medium on microalgal metabolism, biomass production and biochemical composition

“…3,4 Providing these nutrients in large quantities for microalgal commercial-scale cultivation can be costly, accounting for ca 15-20% of the cost. 5 To address this issue, researchers have explored alternative cultivation strategies for microalgae using various types of wastewaters, including anaerobic digestate abattoir effluent, 2,6 sanitary landfill leachate, 7 textile dye effluent, 8 olive mill waste 9 and aquaculture and aquaculture wastewaters. 10,11 These studies have been focused on evaluating the ability of microalgae to remove N and P efficiently, and in some cases, heavy metals from wastewater.…”