Microbial fortification during vermicomposting: A brief review

Vermicomposting is an earthworm-mediated degradation process. It results in a peat-like cast with high water retention capacity and nutrient-rich substrates. Earthworm gut plays a vital role in the process of nutrient solubilization, bioremediation, and fortification of the beneficial microbe population. Microbial diversity analysis shows the presence of Nitrobacter, Azotobacter, Rhizobium, phosphate solubilizing bacteria, nitrogen-fixing bacteria, Ascomycetes, Basidiomycetes, etc. in vermicast. Diversity varies based on bioconversion methods. Gammaproteobacteria and Actinobacteria are reported to be abundant in vermicompost, whereas Alphaproteobacteria and Bacterioides are more prominent in conventional compost. The application of vermicompost improves soil health and promotes plant growth. This review focuses on understanding the metagenomics of microbial populations based on the feedstock composition, earthworm species used during vermicomposting, and how their diversity can affect the nutrient dynamics and metal sequestration process. This review also elaborates on how microbial biomass, number, and diversity affect soil fertility under vermicompost, compost, and conventional inorganic fertilization systems.