Inoculation enhances directional humification by increasing microbial interaction intensity in food waste composting

Inoculation can effectively improve the recycling level of organic waste in composting process. However, the role of inocula in the humification process has been rarely studied. Therefore, we constructed a simulated food waste composting system by adding commercial microbial agents to explore the function of inocula. The results showed that adding microbial agents extended the high temperature maintenance time by 33% and increased the humic acid content by 42%. Inoculation significantly improved the degree of directional humification (HA/TOC = 0.46, p < 0.001). The proportion of positive cohesion in the microbial community underwent an overall increase. The strength of bacterial/fungal community interaction increased by 1.27-fold after inoculation. Furthermore, the inoculum stimulated the potential functional microbes (Thermobifida and Acremonium) which were highly related to the formation of humic acid and the degradation of organic matter. This study showed that additional microbial agents could strengthen microbial interaction to raise the humic acid content, thus opening the door for the development of targeted biotransformation inocula in the future.