Indigenous bacterial bioremediation: Chromiumreducing capabilities of native strains from Halmahera

Indonesia, with its abundant natural resources, faces significant environmental degradation from open-pit mining, that lead to deforestation and heavy metal contamination, which pose dangers to humans and ecosystem. While bacterial bioremediation of heavy metals is well-documented, studies on chromium bioremediation using indigenous Indonesian bacteria remains scarce. This study characterizes chromium-reducing bacteria isolated from post-mining soil in Halmahera, Indonesia, and evaluates their potential for both bioremediation and reforestation of post-mining lands. Macroscopic analyses were used to determine the genus of the Halmahera bacterial isolates and their chromium reducing-capability was assessed using Diphenylcarbazide (DPC) method. Notably these isolates achieved a chromium reduction efficiency of up to 39%, slightly lower than 50% reduction by Pseudomonas aeruginosa in another study, as well as exhibiting phosphate solubility index of 0.66, which shows the bacteria potential to promote plant growth. Our findings demonstrate that these indigenous bacteria are promising candidates for sustainable bioremediation efforts, effectively reducing chromium contamination and simultaneously accelerating reforestation in post-mining areas. This dual action contributes to developing scalable, eco-friendly strategies to mitigate environmental damage caused by mining in Indonesia and similar post-mining environment globally, potentially paving the way for industrial applications in environmental restoration.