Figure 4: CO₂ assessment in the cell-free complete culture medium.

The cell-free culture medium was incubated for 24 h in the presence or absence of 5 mM sodium L-glutamate. After treatment, sodium 2-ketobutyrate was added (final concentations: 0.5–15 mM, respectively). The CO₂ level was determined using cis-[Cr(C₂O₄)(pm)(OH₂)₂]⁺ and a stopped-flow technique. Data are presented as mean ± SD of three independent experiments. *p < 0.05, **p < 0.01 statistically significant differences between samples incubated in the presence and samples incubated in the absence of 5 mM L-glutamate.