Roles of bacterial community in the transformation of organic nitrogen toward enhanced bioavailability during composting with different wastes

[Display omitted] •Composting can increase the bioavailability of organic-N.•CM has more bacterial taxa related with bioavailable organic-N than MSW and GW.•High-molecular-weight BON were degraded into low-molecular-weight by core bacteria.•Moisture, C/N and pH can be used to regulate BON transformation during composting. This study aimed to explore the roles of bacterial community in the transformation of bioavailable organic-N (BON) during different wastes composting. BON fractions with different forms and molecular weights were identified in this study. Results indicated that core bacterial communities improved the availability of BON by degrading high molecular weights BON into low molecular weights BON during different wastes composting. A total of fifty-two core bacterial genera involved in BON transformation were identified by network analysis. Three types of high molecular weights BON fractions (amino acid-N, amine-N and amino sugar-N) were degraded by bacteria during chicken manure and garden waste composting, while only amine-N was degraded during municipal solid waste composting. Finally, moisture, C/N and pH were identified as the key operational parameters affecting BON transformation mediated by microorganisms, which can be used to improve bioavailability of organic-N and reduce N loss during composting.