Pre‑inocula test
Three media were used (LB, E, and LBGlu) for the evaluation
of the influence of the pre-inoculum medium on subsequent
γ-PGA production (which was carried out in medium
E). For the preparation of inoculum, a loopful of cells was
inoculated into Erlenmeyer flasks containing the specific
medium, and incubated at 37 °C and 180 rpm on a rotary
shaker. The inocula for all cultivation essays were standardized
to 1.0 ± 0.1 OD (optical density) at 600 nm and were
added to culture medium at 10 % (volume fraction). The
cultivation was carried out at 37 °C and 180 rpm, on a rotatory
shaker for 96 h. Samples were taken along the time
course of cultivations to quantify γ-PGA, viable cells, citric
acid, glutamic acid, and glycerol. All the experiments were
carried out in duplicates. The inocula for all cultivations
were standardized as described above.