Carotenoids and pH of the culture medium play an important role in displaying metal stress in batch and semi-continuous cultures of Anabaena doliolum

摘要

We analysed the responses of Anabaena doliolum to elevated levels of copper and zinc in batchand semi-continuous cultures. Approximately 10, 4 and 8 and 5-times greater inhibition in final yield ofA. doliolum occurred at 1, 2 tM Cu and 2.5 and 5 tM of Zn, respectively, in semi-continuous culture incomparison to batch culture. Protein, chlorophyl a and carotenoid contents of A. doliolum showed sig-nificantly (P < 0.05) higher inhibition by test metals in semi-continuous culture than in batch culture. Thegreater sensitivity of different parameters of the test organism was related to the high metal content of thecells grown in semi-continuous system. Moreover, enhancement of pH of the culture suspension in batchculture showed a negative relationship with metal accumulation, and therefore with toxicity. This was dueto decrease in free ionic concentrations of test metals. Carotenoids acted as a metal detoxifying agent byminimizing metal-induced inhibition in batch culture as was evident from its negative relationship with metaltoxicity.