Effects of sodium selenite on the growth, biochemical composition and selenium biotransformation of the filamentous microalga Tribonema minus

[Display omitted] •Na2SeO3 exerted dual effects on T. minus growth and antioxidant capacity.•Na2SeO3 promoted carbohydrate and protein accumulation but reduced lipid content.•Tribonema minus exhibited efficient selenite removal, which accumulated in biomass.•It mainly accumulated organic selenium (>93 %), predominately as selenocysteine. This study aimed to investigate the physiological and biochemical responses of filamentous microalga Tribonema minus to different Na2SeO3 concentrations and its selenium absorption and metabolism to evaluate the potential in treating selenium-containing wastewater. The results showed that low Na2SeO3 concentrations promoted growth by increasing chlorophyll content and antioxidant capacity, whereas high concentrations caused oxidative damage. Although Na2SeO3 exposure reduced lipid accumulation compared with the control, it significantly increased carbohydrate, soluble sugar, and protein contents, with the highest carbohydrate productivity of 117.97 mg/L/d at 0.5 mg/L Na2SeO3. Furthermore, this alga effectively absorbed Na2SeO3 in the growth medium and converted most of it into volatile selenium and a small part into organic selenium (predominantly as selenocysteine), showing strong selenite removal efficacy. This is the first report on the potential of T. minus to produce valuable biomass while removing selenite, providing new insights into the economic feasibility of bioremediation of selenium-containing wastewater.