Optimization of selenium biofortification by liquid fermentation based on 2,4-dichlorophenoxyacetic acid and its effect on nutritional value of Pleurotus ostreatus

Pleurotus ostreatus is one of the most popular edible mushrooms worldwide and has been proposed as a candidate for human selenium (Se) supplementation. The objective of this study is to develop a Se-biofortification method by liquid fermentation and evaluate the effect of 2,4-dichlorophenoxyacetic acid (2,4-D), Na₂SeO₃ fortification doses and initial pH on P. ostreatus mycelium growth, nutritional value, and mineral accumulation. The optimal growth conditions were identified as 2,4-D 2.00 mg L⁻¹, Na₂SeO₃ 30.65 mg L⁻¹, and initial pH 5.97 by Box-Behnken design. The optimization resulted in the biomass of 15.75 g L⁻¹ and the organic Se content of 594.85 mg kg⁻¹, which was 2.50 and 8.03 times higher than the control group, respectively. In parallel, the contents of polysaccharides, proteins, essential amino acids, major functional components, and several minerals in mycelium were increased to varying degrees. Overall, this study will provide an experimental basis for the use of P. ostreatus mycelium as a good carrier for organic Se enrichment by liquid fermentation and technical support for the industrial development of new Se biofortification methods.