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Abstract
Heavy metals (HMs) pollution is a serious problem, worldwide. The present study focuses on HMs removal (HMs mobility restricted within soil) by microbial induced mineral precipitation (MIMP) using indigenous isolates. Indigenous isolates were identified as Bacillus subtilis C(225)(MK334652), Oceanobacillus indicireducens 5(225)(MK334653), and Bacillus pumilus 7(225)(MK334654) by 16S-rRNA from HMs polluted industrial-soil (soil-225) that is used for bioremediation. The studied soil contained high level (mg/kg) of Cr(307.41 ± 1.02), Cu(576.35 ± 1.02), and Zn(708.81 ± 1.50) as per Taiwan permissible limit (TPL) and/or Canadian Soil Quality Guidelines (CSQG). Minimum inhibitory concentration (MIC) of Bacillus species were higher compare to Oceanobacillus. Bioavailable-fraction (F1) of HMs (Cr/Cu/Zn) in untreated 225-soil was noticed to be higher compared to F2–F5 fraction. Bacillus subtilis C(225) are more efficient for HMs-mineralization, compared to other isolates where Cr/Cu/Zn immobilized within soil, transforming from bioavailable-fraction (F1) (high-mobility) (60–90% reduction) to residual-fraction F5 (low-mobility) (50–80% increment). Organic-bound-fraction (F4) (medium-mobility) of Cr increased (42.66 ± 2.1%), compared to Cu/Zn, by Bacillus subtilis C(225). Urease (40.8%) and dehydrogenase (8.3%) activity increased in bio-remediated soil, compared to control. MIMP of HMs by ingenious bacteria reflects the transformation-pathway from F1 to F5 of HMs to fix strongly within soils with inadequate mobility. Thus, MIMP by indigenous microbe can be applicable for HMs stabilization/removal in contaminated soil for ecofriendly environmental cleanup.