The Effect Of Nitrogen On The Physiology Of Porphridium Cruentum And Preliminary Research Of Protease In Porphridium Cruentum

Porphyridium sp.’s growth can be affected by different nitrogen source. In this study, resistance and metablisium to nitrogen of Porphyridium sp. was investigat-ed.The PE degradation and purification of protease is mainly discussed.The growth and NO production of Porphyridium sp. in different nitrogen stress were measured respectively. The results showed that Porphyridium sp could utilize both ammonia and nitrate. From over all level, Porphyridium sp. utilize nitrate more efficiently. And in the nitrate concentration of12mmol/L is the best, It also showed that Porphyridium sp would be under stress in either the circumstance of too high or too low(4mmol/L) nitrogen concentration(16mmol/L). But there is a threshold of ammoniac content,0.4mmol/L of ammonia could promote the growth of Porphy-ridium sp, high concentration of ammonia would be a kind of stronger stress than nitrate, the growth was inhibited at4and8mmol/L of ammonia. During the whole growth process, NO production was coordinated with stress strength, which can monitor the stress strength of Porphyridium sp.,and reflect the environment change of the body.NO was relevant to the stress strength except the nitrogen deficiency. NO production was low at nitrate condition, but when at ammoniac stress, NO production was higher with ammonia rised at the period of delay. Compared to nitrate stress, NO production was higher, reflecting that algae was suffered stress of in varied degree. In logarthmic growth phase and stationary phase, NO was relatively low, but rised in decline phase. Porphyridium sp. was in different dgree of stress in ammonia culture medium because NO production was higher in ammonia culture medium than nitrate medium. There was a special case-nitrogen deficiency. In this case, NO production was least, but algae was also in strong stress according to other changes of physiology. This is an protection mechanism, avoiding consuming more energy and nitrogen.Under different nitrogen stress, MDA of Porphyridium sp. reflected the lipid peroxidation of membrance. For instance, the accumulation of un-eliminated substa- nces produced, like MDA (Malonaldehyde), will be increased. At12mmol/L of nitrate and lmmol/L of ammonia, MDA production was lower than other nitrogen stress. What’s more, the enzymatic activities of the antioxidant enzymes will be increased, like SOD (Super Oxide Dismutase) and CAT (Catalase). The body stimulates the antioxidant enzymes to clear the reactive oxygen. At the optium conditions, antioxidant enzymes activities ware low and didn’t change a lot during the whole growth process. The SOD and CAT activities was largen as stress went strong. But if stress was too strong, cell metabolism system was destroyed, and antioxidant enzymes system was damaged, so SOD and CAT activities decreased.In nitrogen deficiency case, there exists "bleaching" phenomenon, this is because of the PBS degradation, and this phenomenon was called "chlorisis", protease might be started in this process. In this paper, we mainly discussed the purification of the protease, through the proteomic techniques, including molecular sieve chromatogr-aphy and ion exchange chromatography and SDS-PAGE, we got a protease from Porphyridium sp., whose molecular weight is about33KD.The optium temperature is40℃, and optium pH is7.5. This protease have a extensive temperature and pH stability. The protease can be stimulated by some metal ions such as Ca2+,and it can be inhibited by pepstatin and benzaminde.