Effects of immobilization process on physiological and biochemical characteristics of Synechococcus

Abstract:

[Background] The Synechococcus is a kind of single celled cyanobacteria grown in ocean. Because of its rapid growth, it is used to purify sewage. In order to reduce the cost, the immobilized method has been adopted in production. However, what does happen in physiological and biochemical characteristics of Synechococcus after be immobilized? There is no report yet. [Objective] This paper studied the changes of physiological and biochemical characteristic and purifying sewage ability of Synechococcus after immobilization in order to provide scientific basis for promoting the application of Synechococcus. [Methods] The Synechococcus was immobilized by sodium alginate and calcium chloride. The growth rate of Synechococcus was determined by microscopic observation. The net photosynthetic efficiency of Synechococcus was detected by dissolved oxygen analyzer. The nitric oxide (NO) content was detected by fluorescence method. The content of chlorophyll and protein, the activity of nitrate reductase (NR) and Rubisco carboxylase and the index of water-quality were detected by spectrophotometer method. [Results] The maximum specific growth rate of Synechococcus was decreased by 24.30% by immobilization. The net photosynthetic rate of immobilized Synechococcus decreased from 9.10% to 29.10% in comparison with that of free Synechococcus. However, there was no significant difference in chlorophyll content between free and immobilizing Synechococcus. The activity of Rubisco carboxylase and NR were decreased by 25.70% and 40% respectively and the NO content was decreased by 32.10% by immobilization process. The removing to total nitrogen, total phosphorus, ammonia nitrogen and nitrite in Takifug rubripes culturing wastewater by Synechococcus were decreased by 30.00%, 17.70%, 20.20% and 21.20% respectively by immobilization process, but it had no effect on removing nitrate and chemical oxygen demand (COD). It is speculated that the immobilization process decreased Rubisco carboxylase activity in Synechococcus by decreasing NO content which regulating Rubisco carboxylase activity by post transcriptional modification. [Conclusion] The activity of NR was inhibited by immobilization process, which resulted in the decrease of NO content, and the latter inhibited the Rubisco activity, akey enzyme of photosynthesis, by posttranscriptional modification. The decrease of Rubisco activity led to the decrease of photosynthetic efficiency, and finally results in the decrease in growth rate and purifying sewage ability of immobilizing Synechococcus.