Biochemical composite material using corncob powder as a carrier material for ureolytic bacteria in soil cadmium immobilization.

Corncob powder possessing its superiority in environmental sustainability and cost, was approved with strong capability of being a replacement of biochar in facilitating the microbial carbonate precipitation process. In this study, the ureolytic bacterial strain Bacillus sp. WA isolated from a pre-acquired metal contaminated soil in Guiyu, China, was showed to be well attached on the surfaces of corncob powder, indicating the carrier's role as a durable shelter for bacterial cells. The efficient immobilization helped develop biochemical composite material (BCM) and proven to function better the calcite precipitation. Afterwards, the mechanism and multi-directional benefits of BCM in edaphic cadmium remediation were examined through pot experiment and compared with corncob powder/bacterial strain/nutrient media as control groups. Integrated lab-scale analyses emphasized the advantages of BCM by the maximum soil urease activity (up to 3.440 U/mg and increased by 214% in 28 days), maximal bacterial propagation (most abundant population in fluorescence microscopy), richest surface functional group (most remarkable OC bond and CO bond in FTIR result), notable calcite precipitation (clear calcite crystals on the surface of BCM compared to control group under SEM-EDS), and highest Cd immobilization rate (exchangeable Cd decreased by 68.54%), among all treatments. The pH and electroconductivity measurements additionally led to the mechanism of corncob powder and NBU promoting pre-existed ureolytic bacteria in soil, which demonstrated the added value of corncob to be fine carbon source and residence shelter for soil microorganism, revealing its potential in developing agricultural materials.