Evidence and mechanism of biological formation of phosphine from the perspective of the tricarboxylic acid cycle

Abstract Phosphine, as a gaseous form of phosphorus, is widely present in the environment and plays an important role in the cycle of phosphorus; however, the formation of phosphine is a mystery. This study investigated, for the first time, the mechanism of phosphine production from the perspective of the tricarboxylic acid cycle. In this work, an anaerobic sequencing batch reactor with L-malic acid and citric acid dosing was developed for phosphine generation. Metabolites and gas components of the microbial tricarboxylic acid cycle were analyzed every 36 h. By means of L-malic acid dosing, phosphine generation was effectively achieved with Enterobacteriaceae dominated dominating. The results show that the tricarboxylic acid cycle produces acetic acid to promote the production of phosphine. Conversely, the production of lactic acid reduces the formation of phosphine. It is inferred that the formation of acetic acid produces reducing power which promotes the production of phosphine, but the formation of lactic acid competes with phosphine for reducing power. This study preliminarily explored the mechanism of microbial production of phosphine, which could provide theoretical guidance for research into the global phosphorus cycle.