固定化过程对聚球藻生理生化特性的影响

Effects of immobilization process on physiological and biochemical characteristics of Synechococcus

摘要:

【背景】聚球藻(Synechococcus)是一类生长于海水中的单细胞蓝细菌，因生长迅速被用来净化污水。为了降低成本，生产上采用了固定化措施，但聚球藻固定化后，细胞内的生理生化变化尚未见报道。【目的】研究聚球藻固定化后生理生化及净化能力的变化，为促进聚球藻的应用提供科学依据。【方法】以海藻酸钠和氯化钙为主要原料固定聚球藻；利用显微观察法计算聚球藻的生长速率；利用溶氧仪检测聚球藻的净光合效率；利用荧光法检测一氧化氮(NO)含量；利用分光光度计法检测叶绿素含量、蛋白含量、硝酸还原酶(NR)活性、Rubisco羧化酶活性及水质指标。【结果】固定化过程使聚球藻的最大比生长速率降低24.30%。固定化后聚球藻的净光合速率降低范围为9.10%?29.10%，但固定化过程对叶绿素含量没有明显的影响。固定化使聚球藻Rubisco羧化酶活性、NO含量和NR活性分别降低25.70%、32.10%和40.00%，使聚球藻去除红鳍东方鲀养殖废水中总氮、总磷、氨氮和亚硝酸盐的能力分别降低30.00%、17.70%、20.20%和21.20%，但对去除硝酸盐及化学需氧量(chemical oxygen demand，COD)的能力没有影响。【结论】固定化过程抑制了聚球藻NR的活性，使其NO产量减少，NO通过转录后修饰的方式降低了光合作用关键酶Rubisco的活性。Rubisco的活性降低使光合效率降低，导致固定化聚球藻的比生长速率和净化污水的能力降低。

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.