Applied Microbiology and Biotechnology, Vol.103, No.19, 7971-7982, 2019
Enhanced calcite precipitation for crack healing by bacteria isolated under low-nitrogen conditions
A nitrogen-starving isolation strategy was developed for the first time to screen bacteria with high calcium-precipitating activity (CPA) for bioremediation of damage in porous media. Meanwhile, a novel mini-tube method based on the detection of insoluble Ca2+ was established to evaluate the CPA of the isolates. A low-nitrogen-demanding strain B6, identified as Bacillus sp., was screened to exhibit the highest CPA (55 mM insoluble Ca2+). Furthermore, the effects of environmental factors and nutrient availability on B6-induced calcium precipitation were evaluated. The results show that nitrate and starch are the best nitrogen source and carbon source with optimal concentration being 4 and 2 g L-1, respectively. The suitable pH range for B6 to precipitate calcium is from 8.5 to 10.5. B6 can maintain the highest CPA at an initial spore concentration of 1.0 x 10(8) spores center dot mL(-1). The optimal CaO2 dosage is 10 g L-1. Finally, the calcite precipitation is confirmed by ESEM, EDS, and XRD analysis.
Keywords:Low-nitrogen-demanding bacteria;Calcium-precipitating activity;Self-healing concrete;Bacillus sp;Microbially induced calcium carbonate precipitation