Changes in earthworm gut associated enzymes and microbial diversity on the treatment of fermented tannery waste using epigeic earthworm Eudrilus eugeniae

Tanneries produce enormous quantities of solid waste including animal fleshing (ANFL) which is a major solid waste generated during pre-tanning operations of leather processing and needs to be disposed of in a safe and environmentally sound way. The aim of this study was to evaluate how the combination of earthworms and microorganisms could enhance the biodegradation of fermented tannery waste mixed with cow dung and leaf litter over a period of 25 days. In our previous study we focused on enzyme activity in fermented waste degradation while this current study revealed the significant role of microbial diversity and population in the Eudrilus eugeniae gut and in vermicompost manure. The maximum microbial population in both studies was recorded on day 21 of the vermicomposting process. Results in this study showed that substantial changes were observed with solid state ferment (SSF) > submerged state ferment (SmF) > control mixtures (p < 0.05). The same trend was identified in earthworm gut enzyme activity. The phytohormones (indole 3-acetic acid [IAA], gibberellic acid [GA3], kinetin) were detected in all treatment vermicompost products. The germination index showed that the vermicomposts from all treatments had no phytotoxic effect on carrot seed (Daucus carota). The overall results confirmed that the microorganisms role were dominant in the vermicomposting process and that it is possible to produce rich manure from fermented tannery waste mixtures.