Urease activity in microbiologically-induced calcite precipitation.

Microbial calcite precipitation is a process of interest in soil stabilization and bioremediation. Prior research has shown that urease activity contributes to this process. However, the exact role of urease in calcite formation remains unclear. This gap motivated the investigation of urease function in calcite precipitation. The study aimed to clarify the relationship between urease activity and calcite formation. Researchers have not yet fully resolved how urease influences calcite precipitation. The need for a detailed mechanistic understanding persists. This uncertainty drove the use of recombinant systems to isolate urease effects.

This study aimed to evaluate the role of urease in calcite precipitation using a recombinant system. The goal was to determine if urease activity is necessary for calcite formation. Researchers focused on comparing urease from two bacterial species. They used Escherichia coli expressing Bacillus pasteurii urease. The study aimed to assess the impact of nickel on urease activity. The researchers also wanted to compare free and immobilized urease. They examined how environmental factors affect urease function. The objective was to clarify the role of urease in calcite precipitation.

The researchers used a recombinant Escherichia coli strain with a plasmid encoding Bacillus pasteurii urease. They compared calcite precipitation between E. coli and B. pasteurii. The study included nickel supplementation to test its effect on urease activity. They used acetohydroxamic acid to inhibit urease and assess its role. Researchers immobilized B. pasteurii urease in polyurethane foam. They measured enzyme kinetics using K(m) and V(max) values. Scanning electron microscopy was used to observe calcite distribution. The study evaluated urease stability under various environmental conditions.

Calcite precipitation by E. coli (pBU11) was significant but less than that by B. pasteurii. Nickel addition at low concentrations increased calcite precipitation by E. coli. Urease inhibition with AHA reduced calcite precipitation in both systems. Immobilized urease showed higher K(m) and lower V(max) values. SEM images revealed calcite precipitation throughout the polyurethane matrix. Immobilized urease retained activity at higher temperatures than free enzyme. The enzyme also remained active in the presence of pronase. These results suggest that immobilization enhances urease stability.

The study confirmed that urease activity is essential for calcite precipitation. The findings suggest that urease function is necessary for this process. Immobilization affected enzyme kinetics but did not prevent calcite formation. The results indicate that immobilized urease can function in different environments. The study supports the idea that urease is a key factor in calcite precipitation. The researchers propose that immobilization may protect urease activity. The data suggest that urease activity is sufficient for calcite formation. The authors conclude that urease plays a central role in this process.