Basics of Construction Microbial Biotechnology - Biotechnologies and Biomimetics for Civil Engineering - page 36

drainage (Park et al. 2010 ; Ogbobe et al. 1998 ; Arunaye and Mwasha 2011 ; Chu
et al. 2009b ), so biodegradability of the material can eliminate the cost of extraction
and disposal of the temporal objects. There could be a big market for biodegradable
bioplastic construction material, which does not require removal and incineration
after use.

2.5 Biocements and Biogrouts

There are possible and used different types of biocementation based on diverse
biogeochemical reactions performed by microorganisms (Ivanov and Chu 2008 ;
Ivanov 2010 ).

2.5.1 Calcium- and Urea-Dependent Biocementation

Most popular type of biocementation is based on so-called microbially-induced
calcium carbonate precipitation (MICCP), which is formation of calcium car-
bonate minerals such as calcite, vaterite, or aragonite on the surface of soil par-
ticles due to: (1) adhesion of cells of urease-producing bacteria (UPB) on the
surface of particle; (2) creating a microgradient of concentration of carbonate and
pH in the site of cell attachment due to hydrolysis of urea by urease of UPB. The
biogeochemical reactions of this biocementation process are as follows:

Urease CO 2 "þ 2NH 4 OH,

ð NH 2 Þ 2 CO þ 2H 2 O ! ð 2 : 2 Þ

Carbonicanhydrase

H þ þ HCO 3 $ 2H þ þ CO 2

CO 2 þ H 2 O $ H 2 CO 3 ! ; ð 2 : 3 Þ

3

CaCl 2 þ H 2 CO 3 ! CaCO 3 #þ 2HCl, ð 2 : 4 Þ

2 HCl þ 2NH 4 OH ! 2NH 4 Cl þ 2H 2 O,

ð 2 : 5 Þ

Total

Urease and carbonicanhydrase

ð NH 2 Þ 2 CO þ 2H 2 O þ CaCl 2 ! CaCO 3 #þ 2NH 4 Cl :

ð 2 : 6 Þ

Enzyme urease (EC 3.5.1.5) is produced by a wide range of microorganisms
because urea is a final product of nitrogen metabolism of human and animals and
plays a role of nitrogen source for many microorganisms in nature. Another
enzyme with important role in MICP is carbonic anhydrase (EC4. 2.1.1) catalyzing
the reversible hydration of CO 2 (Dhami et al. 2014 ).