Accumulation and Chemical Form of Cadmium in Lentinus edodes

Abstract

Because the level of cadmium (Cd) in Lentinus edodes (L. edodes) was the highest among all vegetable foods tested, the accumulation and chemical form of Cd in L. edodes was investigated.1. The mean level of Cd in L. edodes was 0.17ppm (wet basis) and was about six times as high as that in vegetable samples (37 species) tested.2. Among 6 kinds of metals present in woods used for the culture of L. edodes, Cd and zinc (Zn) were concentrated about six and three times in L. edodes cultured on the woods, respectively, whereas the concentration factors of other metals were less than 0.7. L. edodes thus appears to accumulate Cd specifically.3. The distribution of Cd in subcellular components of L. edodes was 45% in the soluble fraction, 26% in the nuclei, 3% in the mitochondria and 3% in microsomes. Cd recovery in this experiment was about 80%.4. Cd in the supernatant obtained by centrifugation of L. edodes homogenate at 16, 000×g for 30 minutes was eluted in Fraction I (Fr-I molecular weight (MW)>ca. 30, 000) and Fraction II (Fr-II MW<ca. 3, 000). The ratio of Cd in Fr-I to Fr-II was approximately 2:1.5. The Cd-binding component in Fr-II had a molecular weight of about 700, gave a positive ninhydrin reaction and had an absorbance maximum at 260nm (pH 8.0). These results suggest that the Cd-binding component of Fr-II is a peptide.