Probiotic-mediated biotransformation of monosodium glutamate to γ-aminobutyric acid: differential production in complex and minimal media and kinetic modelling.

Lactic cultures were screened for their ability to
accumulate γ-aminobutyric acid (GABA) in the culture
medium. Lactobacillus bulgaricus CFR 2028 produced the
highest yields of GABA (22.7 mM) from the substrate
monosodium glutamate (MSG). Instrumental characterization
by high-performance liquid chromatography and structural
characterization by mass spectrometry confirmed
GABA production by L. bulgaricus CFR 2028. The differential
production of GABA in complex and minimal media
indicated that minimal medium (modified tryptone, yeast
extract and glucose; TYG) supported the highest production
of GABA (37 mM), thereby signifying that the acidic pH
alone could have a significant bearing on the yield of
GABA. This observation opens up avenues for the optimization
of the medium components for yield maximization.
The biotransformation kinetics of MSG was examined in
batch experiments by varying initial MSG concentration (1–
5 %). The Monod model was fitted to determine the kinetic
parameters under the MSG uninhibited domain, and the
MSG inhibited domain was represented well by Briggs–
Haldane model.