光氧环境对紫色硫细菌YL28去除无机三态氮的影响

Effect of light and oxygen on the removal of inorganic nitrogen by Marichromatium gracile YL28

摘要:

【背景】光和氧是制约光合细菌生长代谢进而影响其除氮效果的重要因素。不产氧光合细菌紫色硫细菌——海洋着色菌(Marichromatium gracile) YL28能以亚硝氮为唯一氮源进行光合生长，对高浓度无机三态氮具有良好去除能力。【目的】阐明YL28菌株除氮效率与光氧环境的交互联系，获得其生物除氮的最适光氧条件。【方法】以高浓度无机三态氮共存海水水体为研究体系，在有光/无光条件下考查装样量(表征体系溶氧状态)对YL28菌株生物除氮活性的影响，并通过响应面分析法对装样量、光照强度和光周期3个主要因素进行优化。【结果】光照且氧浓度较低时(80%装样量)，YL28具有最佳生长和无机三态氮去除能力；装样量在10%?100%时，菌体生物量(OD660)在0.938?2.719之间，当氨氮、亚硝氮和硝氮分别为7.16、5.67和4.83 mmol/L时，其去除率分别在71.44%?89.09%、99.22%?99.83%和91.60%?97.33%。黑暗条件下，装样量在20%?100%时，氨氮、亚硝氮和硝氮去除率分别在48.07%?64.27%、73.51%?86.42%和42.57%?46.34%，但菌体生物量(OD660为0.615?0.903)明显降低。通过响应面优化，当装样量、光照强度和光周期分别为80.0% (溶氧量约为0.32 mg/L)、2 800 lx和24L:0D时，细胞生长和氨氮去除活性达到最佳状态，分别比优化前提高了21.28%和14.11%。在实际应用中，选取72%?89%装样量(溶氧量约为0.26?0.63 mg/L)、2 240?3 460 lx光照强度和21L:3D?24L:0D光周期，细胞活性可达95%以上。【结论】80%装样量有助于促进菌体光照生长和除氮；在黑暗有氧和无氧环境下，YL28菌株也具有较好除氮活性，这为不产氧光合细菌在生物反应器中高效去除无机三态氮的应用提供了有价值的参考数据。

Abstract:

[Background] Light and oxygen are important limited factors for cell growth and the inorganic nitrogen removal of anoxygenic phototrophic bacteria (APB). Marichromatium gracile YL28, a member of purple sulfur bacteria in APB, can grow with nitrite as the sole nitrogen source and efficiently remove inorganic nitrogen. [Objective] This work aims to explore the relationship between light and/or oxygen and the removal efficiency of inorganic nitrogen by YL28, and acquire the optimal condition of light and oxygen for biological nitrogen removal processes. [Methods] A simulated seawater system with high concentration of co-exist inorganic nitrogen was used to investigate the effect of sample loading quantity (SLQ, it represents dissolved oxygen level) on the inorganic nitrogen removal efficiency by YL28 under the light or dark conditions. The three major factors of SLQ, light intensity and photoperiod were optimized by the response surface analysis. [Results] Under the light condition, the highest removal efficiency of inorganic nitrogen and cell growth were achieved at 80% of SLQ. When SLQ was in the range of 10% to 100%, the range of biomass value (OD660) was from 0.938 to 2.719 and the removal rate of ammonia, nitrite and nitrate reached 71.44%?89.09%, 99.22%?99.83% and 91.60%?97.33% when exposed to 7.16, 5.67, 4.83 mmol/L of ammonia, nitrite, nitrate, respectively. Under the dark condition, when SLQ was in the range of 20% to 100%, the removal rate of ammonia, nitrite and nitrate reached 48.07%?64.27%, 73.51%?86.42% and 42.57%?46.34%, respectively, however, the biomass (OD660, 0.615?0.903) decreased significantly. The response surface analysis showed that the cell growth and ammonia removal efficiency were increased by 21.28% and 14.11% under the 80.0% of SLQ (dissolved oxygen (DO) is approximately 0.32 mg/L), 2 800 lx of light intensity and 24L:0D of photoperiod condition. In practical application, more than 95% of cell activity was achieved under 72% to 89% of SLQ (DO is in the range of 0.26 to 0.63 mg/L), 2 240?3 460 lx of light intensity and 21L:3D?24L:0D of photoperiod conditions. [Conclusion] The 80% of SLQ is of benefit to YL28’s phototrophic growth and the inorganic nitrogen removal efficiency; YL28 remains the good nitrogen removal activity under anaerobically and/or aerobically in the dark. This study provides useful information for the removal of inorganic nitride by APB in bioreactor.