Physiological Responses To Cd Stress In Spirulina And The Cd Uptake Capability By Growing Spirulina Cell

Under CdCl₂ stress, the changes of physiological properties of Spirulina and Cd uptake activity by growing Spirulina were studied, and the detoxification mechanism was also discussed preliminarily. Here were some important results:1. Adding methods of CdCl₂ had little effect on the Cd tolerance of S. platensis. Adding CdCl₂ at the first day, the inhibiting concentration (IC₅₀) at 96h was 25.8mg/L. During the process, the pH of substrate changed from 8.5 to 10.5, and precipitation of Cd(OH)₂ was not observed. The soluble protein, Phycocyanin (PC) and Allophycoyanin (APC) were all reduced under CdCl₂ stress. Pigments slightly increased, while Chlorophylls a was damaged severely at 24mg/L.2. The physiological response of S. platensis to CdCl₂ was complicated. The difference between tests was not observed when only observing the growing curves, but the activities of enzyme had been changed drastically. Besides, the remarkable enhancement of malonyl dialdehyde (MDA) appeared to be an obvious physiological response due to Cd²⁺ treatment.3. The results showed that both S. platensis and S. maxima had a high tolerance to CdCl₂, even growing in the 24mg/L concentration. Extracellular adsorption was bigger than intracellular accumulation in total biomass biosorption, both in 5. platensis and S. maxima cultivated in lower concentrations (6～12mg/L) after 10 days or 6²4mg/L concentrations after 96 hours. Especially S. platensis, the ratio of extracellular adsorption to the total was above 90%. However, the intracellular accumulation sharply increased, even bigger than extracellular adsorption in S. maxima under high concentrations (6²4mg/L) of CdCl₂ after 10 days.4. The production of MTL was increased when S. maxima exposed to CdCl₂, but the same results were not observed on 5. platensis. This fact showed that there were different detoxification mechanisms between the two Spirulina, And S. maxima, the mainly detoxification mechanism was inside of cell, while that of 5. platensis was outside of cell. The activity of GSH-PX increased or decreased irregularly. The morphological changes of S. platensis were also studied. The ultrastructure of...