Accumulation and biotransformation of selenium in kelp Laminaria japonica

Accumulations of selenium in kelp(Laminaria japonica) cultured in seawater were achieved by adding selenite(Na₂SeO₃) with or without N and P(NaNO₃+NaH₂PO₄) nutrient of different concentrations.Biotransformation of selenium in the Kelp was investigated through measuring the selenium of biological samples and different biochemical fractionations.The results show that the total selenium contentin kelp(fresh weight) is 0.451~0.577 Lg/g before accumulation.The optimal concent ration of Na₂SeO₃ is 200 mg/dm³ and the concentration of selenium is 20.558~25.811 Lg/g after exposing for 56 h in seawater containing 200 mg/dm³ Na₂SeO₃.This demonstrates that the kelp has good capability of accumulating selenium.Analysis of selenium composition in the kelp(control group) shows that selenium is predominately present as organic selenium which is up to 86.22% of total selenium.When the kelp exposing for 56 h in seawater containing 200 mg/dm³ Na₂SeO₃,the total selenium is 24.481 Lg/g in which organic selenium is 16.703 Lg/g,inorganic selenium 4.714 Lg/g.The capability of accumulation of selenium was further enhanced by adding N-Pnutrent to the selenite enriched medium.Total selenium is increased by 33.649 Lg/g atoptimal concentration of N-Pnutrient(150 mg/dm³ NaNO₃ and 25 mg/dm³ NaH₂PO₄),whereas theinor ganic selenium is not increased and kept as 4.497 Lg/g,and the increased part of selenium is organic selenium.This implies that kelp Laminari ajaponica could effectively transform inorganic selenium into organic selenium through metabolism.