Exposure to ZnO-NPs enhanced gut- associated microbial activity in Eisenia fetida

With advent of the nanotechnology era, the environmental risk has continuously been receiving engineered nanomaterials, as well as their derivatives. Our current understanding of the potential impact of nanomaterials and their effect on soil organism is limited. The present study fills the gap between effect of manufactured nanomaterials (NPs) and their available natural scavengers. In the study,  earthworm Eisenia fetida (EW), which occupies 60 to 80% of the total biomass and well known for its contribution to cellulolytic degradation of organic wastes, was exposed to ZnO-NPs. Findings suggests that E. fetida can survive even at high exposure of ZnO-NPs (10 mg/kg) and can exhibit increase in bio-accumulation of Zn content in its body tissue with decreased NPs. Exposure of 35 and 10 nm ≥3.5 mg/kg sized NPs showed an increase in cellulase activity by 38 to 41%. This increase in cellulolytic activity in EWs’ gut may also be helpful in the bioconversion of lignocelluloses waste. Eighteen strains of cellulose hydrolytic bacteria capable of producing cellulase were obtained from the guts of EWs exposed to ZnO-NPs. The results of biochemical and 16SrRNA gene sequence examinations showed that six strains belongs to Bacillus sp.; five strains belongs to the sublines of Bacillus and others belongs to the Pseudomonas sp. The study advocates the application of ZnO-NPs enhance gut-associated microbial activity. Key words: Cellulose hydrolytic bacteria, ZnO-NPs, E.fetida, Gut -flora.