Abstract
BackgroundDue to the problems we face today, such as wastewater pollution of aquifers and climate change, it is necessary to search for environmental solutions that help us minimize this problem. An alternative solution might be the cultivation of microalgae that are efficient in the purification of wastewater, removal of greenhouse gases and production of biomass that can be used for the production of biofuels such as biodiesel, methane, bioethanol, among others. The aim of this work is to cultivate five strains of microalgae native in Mexico: Chlorella miniata, Coelastrella sp., Desmodesmus quadricauda, Neochloris oleoabundans and Verrucodesmus verrucosus. The cultivations were performed using municipal wastewater and a foliar fertilizer with the further purpose of assessing their capacity to produce various types of biomass, in particular lipids.MethodsThe experiments were carried out using triplicate 16-L glass bioreactors assays with a 12:12 light–darkness cycle at 25 °C ± 1 under constant aeration. Every 3rd day, a 1-mL sample was taken to determine cell density. In the stationary growth phase, each culture was harvested by sedimentation and lipid content analysis was performed. The biomass with the highest concentration of total lipids was subjected to an analysis of the methyl esters of fatty acids.ResultsAn ANOVA test showed significant differences between the growth rates (F = 6.8, p = 0.0001). The species that were able to produce biomass with the highest concentrations of total lipids were Coelastrella sp. with 44–46%; Verrucodesmus verrucosus with 43–44% and Neochloris oleoabundans 35–37%. As the analysis of the methyl esters of fatty acids showed, the species Coelastrella sp. and V. verrucosus produced lipids composed of 82.9% and 91.28% of fatty acids, respectively, containing C16–C18 carbon chains.ConclusionsAll the species used in the present study were able to grow on wastewater and produce high concentrations of lipids. Therefore, the demands for biodiesel production could be met in the immediate future after continuing working with different microalgae species. Therefore, it is necessary to determine their adaptation potential to grow on contaminated effluents and produce lipids that can be used for the benefit of people and environment.
Highlights
Due to the problems we face today, such as wastewater pollution of aquifers and climate change, it is necessary to search for environmental solutions that help us minimize this problem
Using the cell growth data for every species, a nonparametric Kruskal–Wallis analysis of variance (ANOVA) test was performed resulting in a value of p = 0.003 ˂ λ = 0.05, and the analysis of multiple comparisons showed significant differences between Coelastrella sp. and Verrucodesmus verrucosus compared to all other species
According to the statistical analysis of the variance (ANOVA) the results regarding the lipid content produced by the strains cultivated in foliar fertilizer (BF) and on municipal wastewater (WW) (Table 4) were not found significantly different (p = ≤ 0.05)
Summary
Due to the problems we face today, such as wastewater pollution of aquifers and climate change, it is necessary to search for environmental solutions that help us minimize this problem. The accumulation of organic pollutants in aquatic ecosystems causes adverse effects on human health and environment These pollutants are introduced as a result of human activities involving industrial, domestic, livestock and agricultural discharges. Bioremediation is the process by which pollutants are removed from the environment by using organisms or parts of them, and as a result, the pollutants are removed or reduced or as in our case, degraded to simple compounds. This new technology is much cheaper and more environmentally friendly than other ones and is very promising for large-scale problem solving [1, 3]. It is important to keep in mind that wastewater can be a potential culture medium for cultivating these microorganisms due to many “collateral” benefits such as biological treatment of polluted water, production of biomass and biofuels [2, 3]
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