Statistical Modeling of Environmental Factors on Microbial Urea Hydrolysis Process for Biocement Production

Table 2

Responses investigated and their definitions.

Responses	Unit	Abbreviation	Definition
Bacterial growth	—	(OD600)	Difference between initial and final optical density of the bacterial cell suspension at the wavelength 600 nm. It represents the bacterial cell growth for each experiment.
Urea hydrolysis potential	mS·cm^−1·M		The proportion of the maximum change in electrical conductivity of the solution to the initial urea concentration for each experiment, .
Lag duration	min.		Time corresponding to the intersection between tangent lines of lag phase and log phase for each experiment.
Specific urea hydrolysis rate	mS·cm^−1·min^−1·M		Rate of urea hydrolysis per initial urea concentration, . was considered as urea hydrolysis rate at log phase, , when was negligible (around 0.15 or less); otherwise it was taken as secant rate, (see Figure 2).