AUTHOR=Gao Mingze , Ling Na , Tian Haiyan , Guo Chunqiu , Wang Qiyao 

TITLE=Toxicity, physiological response, and biosorption mechanism of Dunaliella salina to copper, lead, and cadmium

JOURNAL=Frontiers in Microbiology

VOLUME=15

YEAR=2024

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2024.1374275

DOI=10.3389/fmicb.2024.1374275

ISSN=1664-302X

ABSTRACT=<sec><title>Background</title><p>Heavy metal pollution has become a global problem, which urgently needed to be solved owing to its severe threat to water ecosystems and human health. Thus, the exploration and development of a simple, cost-effective and environmental-friendly technique to remove metal elements from contaminated water is of great importance. Algae are a kind of photosynthetic autotroph and exhibit excellent bioadsorption capacities, making them suitable for wastewater treatment.</p></sec><sec><title>Methods</title><p>The effects of heavy metals (copper, lead and cadmium) on the growth, biomolecules accumulation, metabolic responses and antioxidant response of <italic>Dunaliella salina</italic> were investigated. Moreover, the Box-Behnken design (BBD) in response surface methodology (RSM) was used to optimize the biosorption capacity, and FT-IR was performed to explore the biosorption mechanism of <italic>D. salina</italic> on multiple heavy metals.</p></sec><sec><title>Results</title><p>The growth of <italic>D. salina</italic> cells was significantly inhibited and the contents of intracellular photosynthetic pigments, polysaccharides and proteins were obviously reduced under different concentrations of Cu<sup>2+</sup>, Pb<sup>2+</sup> and Cd<sup>2+</sup>, and the EC50 values were 18.14 mg/L, 160.37 mg/L and 3.32 mg/L at 72 h, respectively. Besides, the activities of antioxidant enzyme SOD and CAT in <italic>D. salina</italic> first increased, and then descended with increasing concentration of three metal ions, while MDA contents elevated continuously. Moreover, <italic>D. salina</italic> exhibited an excellent removal efficacy on three heavy metals. BBD assay revealed that the maximal removal rates for Cu<sup>2+</sup>, Pb<sup>2+</sup>, and Cd<sup>2+</sup> were 88.9%, 87.2% and 72.9%, respectively under optimal adsorption conditions of pH 5-6, temperature 20-30°C, and adsorption time 6 h. Both surface biosorption and intracellular bioaccumulation mechanisms are involved in metal ions removal of <italic>D. salina</italic>. FT-IR spectrum exhibited the main functional groups including carboxyl (-COOH), hydroxyl (-OH), amino (-NH2), phosphate (-P=O) and sulfate (-S=O) are closely associated with the biosorption or removal of heavy metalsions.</p></sec><sec><title>Discussion</title><p>Attributing to the brilliant biosorption capacity, <italic>Dunaliella salina</italic> may be developed to be an excellent adsorbent for heavy metals.</p></sec>