Effects of Leaf Substrate, pH and Agitation on Ureolytic Calcium Carbonate Precipitation by Bacillus subtilis

The role of microbial carbonate precipitation (MCP) in concretion formation and fossil preservation has been recently proposed. This study examines the effect of organic matter presence, in the form of Ginkgo biloba and Davallia fejeensis leaves, on MCP by Bacillus subtilis strain PY79 at various pH and agitation. The results of this study demonstrated that the presence of an organic substrate led to higher calcite precipitation under agitation. The highest urea hydrolysis and Ca2+ depletion were observed in treatments initiated at neutral pH. The surface properties and biochemical differences of the leaves may have influenced the efficiency of calcium carbonate precipitation by affecting bacterial growth and the conditions associated with carbonate biomineralization by B. subtilis PY79. Our results demonstrated that the presence of organic substrates increases MCP. Future research will target the role of microbial mats from the natural environment in carbonate precipitation and leaf mineralization.