Nanobiochar loaded microbial consortia based bioremediation of heavy metal contaminated soils enhances sustainable rice biomass production and quality

Abstract

Heavy metal contamination of agricultural soils poses a serious threat to sustainable crop production, environmental quality, and food safety, highlighting the need for environmentally friendly remediation technologies. This study developed a nanobiochar-loaded microbial consortia system as a green strategy for the simultaneous remediation of heavy metal contaminated soils and improvement of rice grain nutritional quality. Heavy metal tolerant Gram-negative bacterial isolates were screened for their tolerance, metal removal capacity, and compatibility for consortium development. Compatible strains were immobilized onto nanobiochar to enhance microbial stability, metal adsorption, and overall remediation efficiency. The selected bacterial isolates effectively removed Pb, As, Hg, Ni, and Cd, with Pb removal ranging from 22.04 to 74.26 mg L -1 . Among the developed formulations, nanobiochar-loaded Consortium-D exhibited the highest remediation performance, achieving Ni and Pb removal efficiencies of 98.22 and 91.13 mg L -1 , respectively.The combined action of nanobiochar adsorption and microbial biosorption/bioaccumulation enhanced heavy metal immobilization while maintaining microbial functionality. In addition to soil remediation, the optimized consortium improved rice grain nutritional quality by increasing Fe and Zn concentrations by 38.5% and 42.1%, respectively, while reducing Pb and Cd accumulation by 68% and 71% compared with the untreated control. Nanobiochar-loaded microbial consortia represent a sustainable and chemical-free bioremediation approach that integrates nanobiochar-assisted metal immobilization with beneficial microbial activities. This multifunctional system offers a promising strategy for reducing heavy metal contamination, improving soil quality, enhancing crop nutritional value, and promoting safer agricultural production.