Characterization of microbial community succession during vermicomposting of medicinal herbal residues

Large amounts of medicinal herbal residues (MHR) are produced in the world annually due to the increasing demand for herbal products. In this study, vermicomposting was used to stabilize MHR. Four inoculating density of earthworms was studied, specifically, 0 (W1), 60 (W2), 120 (W3) and 180 (W4) earthworms per kilogram of substrate. The C:N ratios of vermicomposts in W2, W3 and W4 were less than 20 by the end of the first week, while the value for W1 was 30.92. This indicates that earthworms promote the stabilization of MHR. In the initial stage, richness and diversity of the microbial community decreased due to earthworm inoculation, and then began to increase. The dominant phyla were Proteobacteria, Bacteroidetes, Basidiomycota and Ascomycota in the substrates. The abundance of the dominant phyla varied according to earthworm density, indicating that earthworms change the microbial composition. The results suggest that MHR can be stabilized by vermicomposting.