Microbial cementation of ureolytic bacteria from the genus Bacillus: a review of the bacterial application on cement-based materials for cleaner production

The world is facing sustainability crisis as the survivability of natural environments and biota life continues to be threatened due to extensive usage of non biodegradable and polluting substances for producing cement-based materials. One alarming situation is the acceleration of global warming and climate change as a result of carbon dioxide release from cement manufacturing to the atmosphere. In another negative scenario, the widespread application of conventional water repellents such as silane and siloxane on cement-based materials poses a serious environmental threat due to their non biodegradability in nature. A viable solution that can be strategized to tackle the environmental issues is to utilize calcite from Bacillus genus bacteria for microbial cementation with the aim to optimize the mechanical behavior of cement-based materials. Bacillus genus bacteria are largely found in natural environments. Their capability to cultivate easily, absorb heavy metals and biocrystallize to form calcite has made the bacteria the promising microbes for biomineralization purpose in construction industry. This article reviews the positive influence of the bacteria at inducing calcite precipitation on cement-based materials. The rates of urea hydrolysis, calcite saturation and calcite precipitation of the bacteria which largely depend on the conditions of growth such as pH, temperature, bacterial cell concentration, calcium concentration and urea concentration are elucidated. Subsequent discussion concentrates on the current trend of crack reparation and surface treatment of cement-based materials, the prospect of developing biomineralized materials using the bacteria, and heavy metal biosorption of the bacteria.