Deciphering the internal driving mechanism of microbial community for carbon conversion and nitrogen fixation during food waste composting with multifunctional microbial inoculation.

In this study, the effects of multifunctional microbial inoculation on food waste composting based on the synergistic property between organic matter degradation and nitrogen fixation were investigated. The results showed that inoculation simultaneously strengthened organic matter degradation by 9.9% and improved the nitrogen content by 20.6% compared with that of the control group. Additionally, spectral analysis demonstrated that inoculation was conducive to the enhanced humification, which was supported by the improvement in polyphenol oxidase activity. Microbial analysis showed that most of the introduced microorganisms (Bacillus, Streptomyces, Saccharomonospora) successfully colonized, and stimulated the growth of other indigenous microorganisms (Enterobacter, Paenibacillus). Meanwhile, the change in microbial community structure was accompanied by the enhanced tricarboxylic acid cycle and amino acid metabolism. Furthermore, network analysis and structural equation model revealed that the enhanced cooperation of microorganisms, in which more carbon sources could be provided by cellulose decomposition for nitrogen fixation.

Insights into the effect of iron-carbon particle amendment on food waste composting: Physicochemical properties and the microbial community.

The effects of iron-carbon (Fe-C) particle amendment on organic matter degradation, product quality and functional microbial community in food waste composting were investigated. Fe-C particles (10%) were added to the material and composted for 32 days in a lab-scale composting system. The results suggested that Fe-C particle enhanced organic matter degradation by 12.3%, particularly lignocellulose, leading to a greater humification process (increased by 15.5%). In addition, NO3--N generation was enhanced (15.9%) by nitrification with more active ammonia monooxygenase and nitrite oxidoreductase activities in the cooling and maturity periods. Fe-C particles not only significantly increased the relative abundances of Bacillus and Aspergillus for organic matter decomposition, but also decreased the relative abundances of acid-producing bacteria. RDA analysis demonstrated that the bacterial community was significantly influenced by dissolved organic matter, C/N, NO3--N, humic acid, volatile fatty acids and pH, while electrical conductivity was the key factor affecting the fungal community.