Kinetic parameters estimation
The lipase reaction rate (V) is related to the substrate concentration
(S) by the Michaelis–Menten equation through a
hyperbolic function with enzyme kinetic constants, that is, maximum reaction rate (Vmax) and intrinsic Michaelis constant (Km).
Vmax is the maximum reaction rate attainable with the given
amount of enzyme, when the enzyme is fully saturated with
substrate. Km is the substrate concentration, which gives half
Vmax, and Km provides information about substrate binding to
the enzyme. In this experiment these kinetic constants were estimated
experimentally for the diluted oily wastewater at low oil
concentrations (0.1–0.5 g O&G/L) using FL and IL. The data
was analyzed using nonlinear regression fittings where the measured
reaction rate (Vmeas) was calculated by computing the
instantaneous rate of FFA release and comparing it with the calculated
reaction rate (Vcal) using the Michaelis–Menten equation
until it matched.
Monod kinetic model was used for estimating the anaerobic
kinetic coefficients. The initial values for the kinetic parameters,
that is, maximum substrate removal rate (k) and half-saturation
constants (Ks) were assumed within the range reported in the literature
[30] and the theoretical methane production (cumulative)
was calculated according to the initial values and compared with
the respirometric results. The average percentage errors (APEs)
between the measured and calculated values were minimized
by changing the initial parameter values. The statistical significance
was verified by comparing true average value with model
value using APE. All the other data was analyzed using Excel
2003 with t-test (paired two samples for means) for parameters
and models at 95% confidence intervals. All data reported are
the average values from duplicate measurements.