Biosorption of strontium ions from simulated high-level liquid waste by living Saccharomyces cerevisiae

Abstract

In this study, the Saccharomyces cerevisiae (S. cerevisiae) was modified by γ-ray. The RNA-seq results reflect that the high γ-ray energies could change some gene fragments, such as deletion, recombination, and mutation. The biosorption of strontium ions (Sr²⁺) to different types of S. cerevisiae (S. cerevisiae (K-0), modified S. cerevisiae (Y-7), and non-living S. cerevisiae (H-K)) from the simulated high-level liquid waste (S-HLLW) was assessed at different experimental conditions. The sorption experimental results show that, under an appropriate condition, γ-ray radiation can enhance its biosorption capacity slightly of Sr²⁺ to S. cerevisiae. The maximum metal uptake and efficiency of Y-7 under S-HLLW were 11.656 mg g⁻¹ and 37.91% at 32 h (wet weight), respectively. They decreased to 9.46 mg g⁻¹ and 30.76% under radiation conditions. SEM-EDX and TEM analysis indicates that Sr²⁺ was adsorbed both on the cellular surface and the inner parts of the cells. Our experimental results fit well to the Langmuir and Freundlich model isotherms (r² > 0.94), and the maximum biosorption capacity values reached q_max > 24.74 mg g⁻¹ at 32 °C. Negative values of ΔG⁰ and positive values of ΔH⁰ were observed, indicating the spontaneous and endothermic nature of Sr²⁺ biosorption on modified S. cerevisiae. The biosorption kinetics follow a pseudo-second-order equation at 32 °C (r² > 0.94). The desorption efficiency of Sr²⁺ adsorbed onto Y-7 was 7.65 ± 0.52%, 76.51 ± 2.13%, and 65.62 ± 2.42% by deionized water, 1 M HCl, and 0.1 M EDTA-Na, respectively. However, they were lower than H-K (18.82, 83.32, and 73.32%). Our findings demonstrate that living S. cerevisiae (Y-7) is a promising sorbent material for the treatment of radioactive process streams.