An insight into kinetics and thermodynamics of gamma-aminobutyric acid production by Enterococcus faecium CFR 3003 in batch fermentation.

In the present study, a kinetic and thermodynamic
model for production of gamma-aminobutyric acid (GABA)
using Enterococcus faecium CFR 3003 is proposed. Differential
production of GABA in complex-minimal media indicated that
the minimal medium (Modified TYG: Tryptone, Yeast extract
and Glucose) supported the highest production of GABA. The
influence of variables such as monosodium glutamate (MSG)
concentration (1–5 %), temperature (25–60 °C) and pH (4.0–
8.0) on GABA production was studied. The kinetics on the rate
of MSG consumption (rs) as a function of MSG concentration
[S] was studied by assuming Monod’s model for the MSGuninhibited
region and Briggs–Haldane model for the MSGinhibited
domain. The experimental kinetic parameters determined
were found to be in good agreement with the predicted
ones. Arrhenius model was used to calculate the thermodynamic
parameters. The activation energy for the growth, activation
enthalpy and entropy for GABA formation were found to be
80.13, 87.29 and 0.273 kJ mol−1 K−1, respectively. A process
product yield (YP/S) of 0.64gGABAg−1MSGcould be reached
with a volumetric rate of GABA formation, QP (0.159 g l−1 h−1)
andMSG consumption QS (0.145 g l−1 h−1), respectively, under
optimized conditions. This contributed to a GABA concentration
of 8 g l−1 at the end of 48 h of fermentation time, which is
2.9-fold higher than that under unoptimized conditions.