Enhancing urease for calcium carbonate precipitation in Lysinibacillus Pakistanensis through nutrient optimisation...

Microbially induced calcium carbonate (MICP) has emerged as a well-documented approach for self-healing concrete, focused on remediating microcracks. In this study, multiple soil-derived bacteria were assessed for suitability in self-healing concrete. Among these, nutrients for L. Pakistanensis were optimised to enhance urease activity and calcium carbonate precipitation. A total of 155 soil isolates were screened using morphological and biochemical tests. In this study, L. Pakistanensis was selected as the most promising strain for further optimisation, studying the response of various nutrients such as yeast extract, nutrient broth, glucose, l-alanine, and inosine, by measuring the urea decomposed and calcium carbonate precipitation. SEM, EDS and FTIR were used to characterise L. Pakistanensis precipitate. L. Pakistanensis hydrolysed 100 % of urea within 72 h and produced up to 0.43 g/100 mL. Nutrient optimisation revealed that germinates in particular l-alanine and inosine, significantly enhancing spore germination and urea hydrolysis, whereas excessive calcium inhibits activity. Previous research has explored self-healing concrete using bacteria, with research on optimising nutrients for L. Pakistanensis remaining scarce. This study provides new insight into a potential alternative bacterium to use in self-healing, accompanied by a preliminary optimised medium, to develop a more efficient and sustainable remediation method for microcracking.