Abstract:

Antarctic bacterium Pseudoalteromonas sp. AN64 producing cold-active protease was used for water purification in this experiment. Effect of strain AN64 on aquaculture seawater was studied from different aspects, including dissoluble oxygen (DO), chemical oxygen demand (COD), ammonia and nitrite nitrogen and pH values. In untreated water, soluble protein content increased and reached the maximum on the 7th day with dissolution of protein. Developing with the time, DO content decreased continuously, while COD content increased and reached its maximum of 9.88 mg/L on the 11th day and sustained at a high level. In the absence of oxygen, some harmful substances, such as ammonia and nitrite nitrogen, increased and came to their maximum on the 9th and 11th day, respectively. The pH value decreased to the minimum of 5.95 on the 9th day. After treatment with Antarctic bacterium producing cold-active protease, protein content in sea water reached the maximum on the 5th day, while DO value kept fairly stable. The maximum content of COD occurred on the 7th day, earlier 4 days than the control did. At the same time, the contents of ammonia and nitrite nitrogen were only 47.7 % and 26.5 % of the control group, respectively. The change of pH was slightly and maintained between 6.85 and 7.52. It indicates that the cold-active protease produced by Antarctic bacterium can hydrolyze effectively protein in water. The low-content protein decreased the production of ammonia and nitrite nitrogen and kept the stability of pH, which provided an effective way for healthy marine aquaculture.

Key words: water purification