Kinetic model of a newly-isolated Lysinibacillus sp. strain YL and elastic properties of its biogenic CaCO towards biocement application.

BACKGROUND

Biocement, calcifying bacteria-incorporated cement, offers an environmentally-friendly way to increase the cement lifespan. This work aimed to investigate the potential use of Lysinibacillus sp. strain YL towards biocement application in both theoretical and experimental ways.

METHODS AND RESULTS

Strain YL was grown using calcium acetate (Ca(C H O ) ), calcium chloride (CaCl ) and calcium nitrate (Ca(NO ) ). Maximum bacterial growth of ~0.09 hr-1 and the highest amount of CaCO precipitation of ~8.0 g/L were obtained when using Ca(C H O ) . The SEM and XRD results confirmed that biogenic CaCO were calcites. The bulk, Young's and shear moduli of biogenic CaCO calculated via the VRH approximation were ~1.5-2.3 times larger than those of ordinary Portland cement. The Poisson's ratio was 0.382 and negative in some directions, suggesting its ductility and auxetic behaviors. The new model was developed to explain the growth kinetic of strain YL in the presence of Ca(C H O ) , whose concentration was optimized for biocement experiments. Strain YL could increase the compressive strength of cement up to ~50% higher than that of the uninoculated cement.

CONCLUSION

Strain YL is a promising candidate for biocement applications. This work represents the trials of experiments and models allowing quantitatively comparison with large-scale production in the future.

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