## 3 Results and Discussion
### BC Biosynthesis on Waste Media  
The effectiveness of biocellulose synthesis by _Ga. hansenii_ ATCC 23769 and _K. xylimus_ K2G30 strains in various waste media was assessed. The obtained results showed that within the same medium, there were no significant differences between waste concentrations for most media (exception of banana peels and celery pomace). Statistically significant differences occurred within the same concentrations for different waste media. This means that for obtaining BC by _Ga. hansenii_, the type of waste was more important than its concentration. The largest yield of BC produced by _Ga. hansenii_ ATCC 23769 was obtained in media with celery pomace with a concentration of 20 g\(\cdot\)dm\({}^{-3}\) (1.79 g\(\cdot\)dm\({}^{-3}\)) and banana peels with a concentration of 70 g\(\cdot\)dm\({}^{-3}\) (1.53 g\(\cdot\)dm\({}^{-3}\); Figure 2). Figure 1: Dry mass of bacterial cellulose obtained in classical media by _Ga. hansenii_ and _K. xylimus_. The same uppercase letters in the same strain for different media are not statistically significantly different. The same lowercase letters in the same medium for different strains are not statistically significantly different. The obtained BC weight values were slightly higher compared with the results obtained in the studies by [PERSON] et al. [28] and [PERSON] et al. [29], where in media based on hydrolyses from celery root and banana peels, 1.08 g\(\cdot\)dm\({}^{-3}\) and 0.89 g\(\cdot\)dm\({}^{-3}\) of BC were obtained by _K. hansenii_ DSM 5602 and _K. nattaicola_ TISTR 2661, respectively [36; 37]. The BC obtained in the media with celery waste at concentrations of 50 g\(\cdot\)dm\({}^{-3}\) and 70 g\(\cdot\)dm\({}^{-3}\) was so delicate and unstable that it underwent significant damage during its removal from the medium (Figure 3). Therefore, its purification and determination were not possible. BC from these medium variants was characterized by numerous embedded celery fibers, which probably reduced its mechanical strength. Similar observations were reached by [PERSON] et al. [38], who analyzed BC obtained in a medium with hemp fibers and observed that biocellulose was characterized by a low value of Young's modulus and low mechanical strength. In celery pomace medium with a concentration of 20 g\(\cdot\)dm\({}^{-3}\), the most BC was obtained; thus, the use of this waste in the future would require one to consider reducing the concentration of waste or applying a pre-treatment, e.g., acid/enzymatic hydrolysis, which would reduce the incorporation of plant fibers into the BC structure. In the medium with fish waste, the smallest yield of BC was obtained, regardless of the concentration used. Fish waste is rich in protein, organic carbon, nitrogen, and phosphorus, but has a low sugar content, which could possibly limit BC biosynthesis [39]. According to current knowledge, this was the first study in which fish waste had been used and described for producing BC. However, there are reports in the literature on fish waste use in the microbiological biosynthesis of other compounds, e.g., lactic acid [40]. In the studies by [PERSON] et al. [40], it was demonstrated that the largest yield of lactic acid was obtained after the initial treatment and acid hydrolysis of fish waste. It was established that the bacteria _Lactobacillus rhannosus_ were not able to absorb protein nutrients without their prior hydrolysis, which also influenced the uptake of, e.g., glucose. On this basis, it can be assumed that, as well as in our study, the lack of hydrolysis of fish waste negatively affected the production of BC by _Ga. hansenii_. Hemp pomace was also used as a waste medium (concentrations of 10, 15, and 20 g\(\cdot\)dm\({}^{-3}\)) for BC biosynthesis. The lowest yield of BC was obtained in a medium with a concentration of 10 g\(\cdot\)dm\({}^{-3}\); however, the BC yield did not differ significantly from the BC yield obtained in the media with a concentration of 15 g\(\cdot\)dm\({}^{-3}\) and 20 g\(\cdot\)dm\({}^{-3}\).