Cellular Stress Conditions as a Strategy to Increase Carbohydrate Productivity in Spirulina platensis

Abstract

Spirulina platensis, when grown under stress, may alter its metabolic pathways, leading to carbohydrate accumulation. Research on the combined effects of stress factors such as UV radiation, photoperiod, and light, and the influence of micronutrients (Ca, Fe, and Mg) on microalgae carbohydrate composition is scarce. The aim of the present study was to evaluate the effects of combined cell stress factors on the microalgal growth and biochemical composition of S. platensis, to apply the biomass in the context of biorefineries. Assays were performed at two cultivation stages: in the first stage, Zarrouk medium (50%) was used until the end of the exponential growth phase (18 days) and, in the second stage, the cells obtained in the first stage were centrifuged and recultivated in 20% Zarrouk’s medium under physical (UV, photoperiod/light, NaCl) and nutritional stress (limitation of Ca, Fe, and Mg concentrations in 20% Zarrouk). The highest carbohydrate yields (27.84 mg L−1 day−1) were obtained in the photoperiod/light intensity-stressed cultures in the medium with nutrient limitation. The study outcomes showed the methods to increase carbohydrate synthesis in cultures under optimized conditions. Our results showed that nutrient limitation by 20% Zarrouk combined with higher light intensity (67.5 μmol photons m−2 s−1) and photoperiod (18-h/6-h light/dark cycles) is an efficient strategy to achieve higher intracellular concentrations (59.71%) and carbohydrate yields (55.85 mg L−1 day−1) in a discontinuous culture method.