Strengthening of Soil Through Microbial Induced Calcite Precipitation Using Acetobacter xylinum

Abstract

In recent years, there has been a sharp increase in the research for technology relating to the alteration in the composition and characteristics of soil utilizing innovative enzymatic methods and unique microorganisms. A focus area for research is Microbial Induced Calcite Precipitation (MICP), which involves the use of bacterial cultures for the precipitation of calcite in the soil for enhancement of its geotechnical properties. In this study, with the isolation of novel ureolytic bacteria, soil samples were taken from marine-based ecosystems and processed aseptically. Initially, a total of 23 morphologically distinct colonies of Ureolytic Bacteria-UB (UB1-UB23) were identified for consecutive primary ureolytic activity screening. Subsequently, the morphologically distinct colonies were subjected to urea hydrolysis and eight isolates, namely UB4, UB5, UB6, UB9, UB11, UB16, UB21, and UB23 were selected for secondary screening based on the zone of inhibition. UB21 (7.09 mM/min) showed the maximum specific urease activity, and thus, selected organisms were subjected to molecular identification and found to be Acetobacter xylinum. The organisms were further tuned for a variety of growth factors, such as calcium carbonate molarity, urea concentration, inoculum size, and reaction time, for effective deposit of calcium and improvement of soil quality. The Acetobacter xylinum-treated soil was subjected to UCS analysis to determine the soil strength, and it was found that at the highest soil density, it was evident that Acetobacter xylinum mediated MICP (Microbial Induced Calcite Precipitation) was able to seal voids and creates a revolution in modern day engineering and constructions.