Abolishing cadmium toxicity in Chlorella vulgaris by ascorbic acid, calcium, glucose and reduced glutathione

Addition of ascorbic acid, calcium (Ca super(2+)), glucose and reduced glutathione (GSH) to the cadmium (Cd super(2+))-amended Kuhl medium significantly accelerated the growth and chlorophyll content of Chlorella vulgaris. This enhancement was found to be dose dependent. Their relative effectiveness against Cd super(2+) on growth and chlorophyll content has been arranged as GSH > Ca super(2+) > glucose > ascorbic acid. However, Ca super(2+) offered more protection against Cd super(2+) toxicity on protein contents, followed by ascorbic acid, GSH and glucose. The different concentrations of all amelioratives completely alleviated the toxicity of Cd super(2+) on total carbohydrates to exceed the control level. Photosynthetic oxygen evolution showed more response to Ca super(2+) and glucose in alleviating Cd super(2+) toxicity. On the other hand, at certain concentrations, GSH, Ca super(2+), ascorbic acid and glucose stimulated respiratory oxygen uptake over the control level. The uptake of Cd super(2+) dropped significantly in cultures supplemented with 20 mu M ascorbic acid, glucose and GSH, while Ca super(2+) (30 mu M) significantly lowered the Cd super(2+) uptake by 58% indicating that Ca super(2+) had a more antagonistic effect against Cd super(2+).