Biofortified vermicompost: Exploring bacterial community dynamics and enzymatic pathways through bacteriome analysis for arsenic bioremediation in mine waste.

The extraction of mica from open-cast mines generates substantial waste, often laden with arsenic, posing severe environmental risks. Addressing this waste is essential to mitigate co-contamination. Vermitechnology offers a promising solution by converting toxic waste into nutrient-enriched, sanitized compost suitable for agriculture. This study explored bioremediation of toxic mine tailings (MT) through aerobic composting, vermicomposting and enriched vermicomposting (with Bacillus subtilis K5BGRD). Earthworm fecundity was impaired in dense MT settings but improved in MT+CD (1:1) treatments. Vermicomposting stabilized pH, enhanced nutrient mineralization and increased potassium bioavailability compared to aerobic composting. Enriched vermicompost reduced bioavailable arsenic by 58-88 % post-maturity, alongside increased microbial diversity and enzymatic activity. Earthworms bioaccumulated arsenic, contributing to a total reduction of 14.25 %. Pearson correlation and PLS-SEM analyses highlighted reduced arsenic-induced stress upon compost maturity. Metataxonomic analysis revealed microbial similarities between V1 (MT+CD [1:1]) and EV1 (MT+CD+B [1:1:1]) composts, with enrichment of stress-resistant, bioremediating and plant growth-promoting taxa. Upon crop trial it was deduced that microbe-mediated vermicomposting, particularly when combined with recommended fertilizer doses (as in T2), not only minimized arsenic accumulation in tomato plants but also significantly enhanced yield, highlighting its potential as a sustainable and effective strategy for safe crop production in contaminated soils. The study demonstrated the symbiotic relationship between earthworms and microbes in waste-treated settings, establishing a novel feedstock combination to remediate hazardous mine waste. Ultimately, this approach has the potential to replace chemical fertilizers, improve crop yields and reduce arsenic exposure - offering a cost-effective and eco-friendly solution to mining waste management.