Graduate School of Engineering, Nagoya University, Chikusa-ku, Nagoya, 464-8603, Japan.
National Institute for Land and Infrastructure Management, Asahi 1, Tsukuba, Ibaraki, 305-0804, Japan.
Sci Rep. 2021 Mar 22;11(1):6567. doi: 10.1038/s41598-021-85955-3.
Nitrogen fertiliser is manufactured using the industrial Haber-Bosch process, although it is extremely energy-consuming. One sustainable alternative technology is the electrochemical promotion of biological nitrogen fixation (BNF). This study reports the promotion of BNF activity of anaerobic microbial consortia by humin, a solid-phase humic substance, at any pH, functioning as an extracellular electron mediator, to levels of 5.7-11.8 times under nitrogen-deficient conditions. This was evidenced by increased acetylene reduction activity and total nitrogen content of the consortia. Various humins from different origins promoted anaerobic BNF activity, although the degree of promotion differed. The promotion effected by humin differed from the effects of chemical reducing agents and the effects of supplemental micronutrients and vitamins. The promotion of anaerobic BNF activity by only reduced humin without any other electron donor suggested that humin did not serve as organic carbon source but as extracellular electron mediator, for electron donation to the nitrogen-fixing microorganisms. The next generation sequencing (NGS) of partial 16S rRNA genes showed the predominance of Clostridiales (Firmicutes) in the consortia. These findings suggest the effectiveness of humin as a solid-phase extracellular electron mediator for the promotion of anaerobic BNF activity, potentially to serve for the basis for a sustainable technology.
氮肥是通过工业哈伯-博世工艺制造的，尽管它极其耗能。一种可持续的替代技术是电化学促进生物固氮（BNF）。本研究报告了腐殖质（一种固相腐殖物质）在任何 pH 值下作为细胞外电子介体促进厌氧微生物群落的 BNF 活性，在氮缺乏条件下可将 BNF 活性提高 5.7-11.8 倍。这可以通过乙炔还原活性的增加和群落的总氮含量来证明。不同来源的各种腐殖质都能促进厌氧 BNF 活性，尽管促进程度不同。腐殖质的促进作用不同于化学还原剂以及补充微量元素和维生素的作用。仅还原腐殖质而没有任何其他电子供体就能促进厌氧 BNF 活性，这表明腐殖质不是作为有机碳源，而是作为细胞外电子介体，将电子供体传递给固氮微生物。部分 16S rRNA 基因的下一代测序（NGS）显示，群落中主要存在梭菌（Firmicutes）。这些发现表明腐殖质作为一种固态细胞外电子介体促进厌氧 BNF 活性的有效性，可能为可持续技术奠定基础。
