Sulfur autotrophic denitrification utilizes elemental sulfur as the electron donor for nitrate removal from aquatic environments. Organic carbon could stimulate the conversion of sulfur and facilitates the S⁰-based denitrification process in the mix-trophic. In this study, the co-cultured system of sulfur reducer (Geobacter sulfurreducens) and Thiobacillus denitrificans was used to investigate that how organic carbon could boost the S⁰-based denitrification. The results showed that the rate of S⁰-based denitrification was improved with C/N ratio of 0.13 and this improvement continued even after the acetate was exhausted. Sulfur probe test and Raman analysis suggested that reduced sulfur species (S_x^2-) were formed with the addition of organic carbon. The S_x^2- could recombine with element sulfur and the bioavailability of S⁰ would be improved, as a result, the rate of S⁰-based denitrification increased as well. Nitrate reduction rate could further increase with the C/N ratio of 0.88, but it would decrease significantly when the C/N ratio increased to 1.50 as the high concentration of generated S^2-. Our results provided explanations that why organic carbon addition would improve the bioavailability of S⁰ which could further promote the S⁰-dominant denitrification process.

硫的自养反硝化利用元素硫作为电子供体，从水生环境中去除硝酸盐。有机碳可以刺激硫的转化并促进混合营养中基于S ⁰的反硝化过程。在这项研究中，减硫剂（Geobacter sulphreducens）和反硝化硫杆菌共培养系统用于研究有机碳如何促进基于S ⁰的反硝化。结果表明，当C / N比为0.13时，基于S ⁰的反硝化速率提高，并且即使在乙酸盐耗尽后，这种改进仍持续。硫探针测试和拉曼分析表明，还原的硫种类（S通过添加有机碳形成_x ^2-）。S _x ^2-可以与元素硫复合，S ⁰的生物利用度得到改善，结果，基于S ⁰的反硝化率也提高了。随着C / N比为0.88，硝酸盐还原率可以进一步提高，但是当C / N比增加至1.50时，由于高浓度的生成的S ^2-，硝酸盐还原率会显着降低。我们的结果提供了解释，说明为什么添加有机碳会提高S ⁰的生物利用度，从而进一步促进S ⁰占优势的反硝化过程。