**3.4 Effects concentration variations of Se2+ and Zn- in fermentation media on dry weight of cell biomass (g), EPS production (g), glucose, and protein levels (%)**

**Table 3** shows that the higher the concentration of Se in the medium, the higher the cell biomass formed. It was inversely proportional to the formation of EPS: the higher the selenium concentration in the medium, the lower the dry weight of EPS. The decrease in EPS yield was due to the increase in selenium concentration in the media because the selenium inhibited the metabolic process of EPS synthesis by *L. plantarum* [51].

The results of Arain *et al.* reported that the addition of mineral treatment could change the pH of the media which caused the inhibition of the growth of *Lactobacillus bulgaricus* due to the high concentration of minerals. Mineral requirements for microbial growth were only in small amounts. This statement supported that the concentration of selenium as a mineral when added at high concentrations can result in inhibition of EPS production. Selenium is essential for the progression and expression of humoral and cell-mediated immune responses. Selenium enhances the phagocytic activity of neutrophil granulocytes and macrophages, and when stimulated in myogens, increases T lymphocyte counts [52].

Zinc is involved in protein synthesis and is a regulator of involved in protein synthesis an is a regulator of synaptic activity and neuronal processes. Zinc deficiency due to the reduced ingestion of this metal causes an abnormal process in the nervous system [51]. The effect of adding Zn2+ to medium with different concentrations is shown in **Table 4**: the higher the zinc concentration in the growth medium, the higher the cell biomass produced. On the other hand, the production




**Table 4.** *Effects of Zn2+ treatment with different concentrations on dry weight of cell biomass (g), EPS production (g), glucose and protein levels (%). The numbers followed by the same letter are not significantly different (P < 0.05).*
