Statistical Modeling of Bacterial Culture Medium Composition Affecting Mineralization in Ferrochrome Ash

Biomineralization is expected as an effective treatment technology to stabilize ferrochrome ash. It operates based on urea hydrolysis principle, and it requires an efficient medium for good bacterial growth and urease activity. An optimal medium is an ideal combination of protein, vitamin, and carbon source in the feed for bacteria. The objective of the current study is to optimize the medium and analyze the significance of its components on bacterial growth and urea hydrolysis. A central composite design (CCD) was developed with 20 experiments with different quantities of soybean (protein), yeast extract (vitamin), and dextrose (carbon) in the medium. Optical density at 600 nm and urease activity were determined after 12 h from inoculation and analyzed using response surface methodology (RSM) in Design-Expert software. Maximum urease activity of 27.83 mM of urea hydrolyzed/min and a maximum optical density of 1.92 were observed with the standard runs 4 and 10, respectively. According to the findings of the current study, the dosages of vitamin source and protein source were significantly affecting urease activity and optical density. It is inferred that the most crucial factor for optical density in the medium is protein dosage, and urease activity is vitamin dosage. Both bacterial growth and urea hydrolysis were minimally affected by the carbon dosage, suggesting that regulating the protein and vitamin doses, combined with a nominal carbon dose, results in an optimal growth medium for the biomineralization in ferrochrome ash.