Algal consortia based metal detoxification of municipal wastewater: Implication on photosynthetic performance, lipid production, and defense responses

Abstract

The present investigation was carried out to assess the competence of artificially engineered microalgal consortia i.e. consortia 1 (Scenedesmus vacuolatus + Chlorococcum humicola), consortia 2 (Tetradesmus sp. + Scenedesmus vacuolatus), and consortia 3 (Chlorococcum humicola + Scenedesmus vacuolatus + Tetradesmus sp.) for municipal wastewater treatment and lipid production under laboratory conditions. The purpose of the present study was to screen the competent microalgae consortia based on wastewater remediation, photosynthetic performance, and antioxidant defense responses. The outcome based on nutrient reutilization (78.98-98%), metal detoxification (50-94%), and biomass production (1.43-1.65 folds) reflected greater adaptability and tolerance of consortia 2 against different concentrations of wastewater. The photosynthetic performance parameters such as active photosystem II reaction centre, the quantum yield, and photosynthetic performance index were increased by 1.20-2.35 folds in consortia 2 after treatment with different concentrations of wastewater. Additionally, Fourier transform infrared spectroscopy peak showed at 1750 cm^-1 confirmed neutral lipid accumulation in consortia 2 at 100% concentration of wastewater. The measurement of oxidative stress markers such as thiobarbituric acid reactive species and hydrogen peroxide showed considerable decline in consortia 2 as compared to consortia 1 and 3. Interestingly, increased non-enzymatic (1.02-2.44 folds) and enzymatic antioxidant (1.05-4.14 folds) activity in consortia 2 reflected that oxidative stress was attenuated by the amplified activity of ascorbic acid, proline, cysteine, superoxide dismutase, catalase, and glutathione reductase. Overall, photosynthetic performance, lipid production, and antioxidants activity represented that the consortia 2 can be effectively used for sustainable wastewater treatment and lipid production. Thus, the synergistic association of two microalgae may be the superior and neoteric paradigm with multilevel benefits such as sustainable nutrient resource utilization, metal detoxification, and lipid production.

Keywords: Antioxidants; Metal detoxification; Oxidative stress; Photosystem II; Resource reutilization.