## 3 Results and Discussion
### BC Biosynthesis in Classical Media  
The obtained results showed that in the case of the _Ga. hansenii_ strain, there were no statistically significant differences in BC biosynthesis on different classical media. For the _K. xylinus_ strain, HS and YPM media differed significantly from GY and GYE media, where BC production was low. In the HS and YPM media, a significant difference was observed in the BC mass obtained by each strain. In both media, more BC mass was obtained through the culture of _K. xylinus_ than _Ga. hansenii_. No statistically significant differences were observed between the mass of BC produced by _Ga. hansenii_ and _K. xylinus_ in both the GY and GYE media. After culturing the _Ga. hansenii_ and _K. xylinus_ strains in classical media, it was found that the GY and YPM media ensured obtaining the highest BC yields (Figure 1). In the YPM medium, a higher yield of BC (5.23 g\(\cdot\)dm\({}^{-3}\)) was obtained from the culture of the _K. xylinus_ strain in comparison with the yield of BC obtained from the culture of _Ga. hansenii_ in the GY medium (3.19 g\(\cdot\)dm\({}^{-3}\)). The HS medium is widely considered to be one of the most versatile and optimized media for obtaining BC [30]. However, in the presented research, the cultures of AAB in the HS medium resulted in obtaining a lower BC mass (1.34 g\(\cdot\)dm\({}^{-3}\) for _Ga. hansenii_ and 4.17 g\(\cdot\)dm\({}^{-3}\) for _K. xylinus_) compared with the cultures in the GY and YPM media, respectively. Therefore, it can be assumed that the efficiency of BC production in the HS medium depends on the strain used [33]. In this study, a low BC yield was obtained in the GYE medium for both of the strains tested (Figure 1). Presumably, the presence of ethyl alcohol in the GYE medium led to inducing AAB metabolism towards its oxidation to acetic acid, instead of using glucose for cell proliferation, which had a direct impact on the low yield of BC biosynthesis [32]. The YPM medium contains mannitol as the carbon source, as well as peptone and yeast extract as the nitrogen source. Glucose is the source of carbon in the HS medium, while nitrogen is supplied through the yeast extract and peptone [28]. For AAB, mannitol might be a better carbon source than glucose, because mannitol metabolism gluconic acid is not produced (as opposed to glucose metabolism), which affects the pH medium changes, which in turn reduces the activity of AAB cells and has an impact on the disturbance of BC biosynthesis [31]. [PERSON] et al. [28] also observed a higher efficiency of BC biosynthesis in the mannitol medium compared with the glucose medium (8.8 g\(\cdot\)dm\({}^{-3}\) and 6.2 g\(\cdot\)dm\({}^{-3}\), respectively). In the case of the GY medium, a clear, but not statistically significant difference between the mass of BC produced by _Ga. hansenii_ and _K. xylinus_ was noted and 2.7 g\(\cdot\)dm\({}^{-3}\) and 0.7 g\(\cdot\)dm\({}^{-3}\), respectively. This is probably because the _K. xylinus_ strain requires a more complex and nutrient-rich medium to produce BC. For example, the media in which _K. xylinus_ produced the largest amount of BC (HS and YPM), other than with glucose and y a yeast extract, were enriched with, among others, peptone, mannitol, Na\({}_{2}\)HPO\({}_{4}\), and citric acid. The low BC yield in the GY medium could be explained by the fact that instead of BC, glucose in this medium could be transformed into gluconic acid and its derivatives [34]. As noted by [PERSON] et al. [35], two energy production pathways exist in AAB: one is the production of phosphates at the substrate level by glucose metabolism, and the other involves the oxidative production of phosphates by the reduced form of nicotinamide adenine dinucleotide (NADH) (or reduced flavin adenine dinucleotide (FADH2)) generated in the process of glucose metabolism and transferred to electron acceptors [35]. In the case of glucose availability, it was phosphorylated to glucose-6-phosphate (G6P) through glucokinase.