Effects of antibiotic supplementation vs. nutrient stress on α-linolenic acid and α-tocopherol in Scenedesmus sp

The hormetic effects of antibiotics on Scenedesmus sp. werecompared with nitrogen limitationstrategies. We observed that 100 and 1000 nM supplementation with antibiotics could stimulate bothα-linolenic acid (ALA) and α-tocopherol productivities. Although nitrogen limitation had the best overall biomass and chlorophyll a productivity (∼ 43.83 % and 109.07 % ↑, respectively), tetracycline (1000 nM, T₁₀₀₀) was the best antibiotic for biomass (∼ 12.08 % ↑) while erythromycin (100 nM, E₁₀₀) was the best for chlorophyll a (∼ 52.19 % ↑). The antibiotics also triggered accumulation of monounsaturated fatty acids, like C16:1 and C18:1, which the nitrogen stress strategies failed to achieve. Rifampicin (100 nM, R₁₀₀) and E₁₀₀, with ∼3.92-4.14-fold increase in α-tocopherol and ∼4.41-4.81-fold increases in ALA productivities, reiterate the role of moderate stresses in stimulating high-value metabolites in microalgae. Our results provide an alternative medium engineering strategy for stimulating algal metabolites without compromising on the biomass. However, further studies are underwaytosafely remediate cultivation effluents and elucidate the physiological mechanisms of individual antibiotics to develop a more holistic strategy for targeted algal farming.