## 3 Results and Discussion
### Identification of Microorganisms in the Extraction Area and Juice Purification
The fresh cosestetes cool the juice coming from the extraction tower through the countercurrent mixer (Figure 1). This step results in a raw juice temperature of approximately 30 \({}^{\circ}\)C. The lower temperature causes the predominance of mesophilic bacteria, such as _Leuconostoc_ and _Lactobacillus_ species (Table 2). This finding supports the results of previous studies based on cultural methods [8; 12; 13]. In addition to the predominating phylum _Frimicutes_ mentioned above, bacteria belonging to the phyla _Proteobacteria_, _Actinobacteria_, _Acidobacteria_, and _Nitrospiraceae_ occur in raw juice. The microbiota of Chinese sugar beets in different growth stages of the plant was identified based on amplicon-based sequencing (Illumina technique) and resulted in bacterial groups of the same phyla as detected in this study [53]. These bacteria may have been washed off from fresh beet cosestetes by the raw juice due to the countercurrent processing principle. In the previous process step, the extraction as well as in the following step, the juice purification, these bacteria could no longer be detected or were only measured at very low relative abundance. In the extraction area, countercurrent mixer and extraction tower (sample 3-5 in Table 2), a mixture of aerobic and anaerobic thermophilic endospore-forming bacteria could be found (Table 2). To extract sucrose from the cosestetes, extraction water is used. This water consists of regenerated water from the regeneration of ion exchangers used to remove calcium from juice after the juice purification process, known as fresh water, and press water generated by pressing the exhausted cosestetes (Figure 1). Bacteria detected in extraction water were rarely found or could not be detected in further steps in the extraction area. This absence of bacteria is observed because the fresh water in the investigated factory is treated with UV radiation. Press water showed high microbial contamination levels [13] and high alpha diversity (Table 3, Figure S1 and Table S1), but these bacteria were not predominant in the juice from the mid-tower or the tower juice. In both extraction lines, the bacterial community was very similar, except for the sampling point at the central part of the extraction tower. In the juice from mid-tower 1, _Lactobacillus_ species were found (Table 2). This finding confirmed the results of a previous study based on culture methods, where a significantly higher number of lactic acid bacteria were detected in these samples from mid-tower 1 [13]. In the samples originating from juice purification, hard juice and thin juice, the calculated alpha diversity was very low (Table 3, Figure S1 and Table S1), and the _Thermus_ species was found to be typical. Additionally, in hard juice, other bacterial species, such as _Burkholderia_ species, could be detected, but this genus was no longer present in thin juice (Table 2). This finding may be attributable to bacteria that remained in the ion exchanger resin usually used for decalcification of the juice and were washed out in the regeneration cycle with the regenerate. Regarding the effect of high temperatures (approximately 80 \({}^{\circ}\)C) on the bacterial community and typical for the resin columns, it could be assumed that the _Burkholderia_ cells are not viable. In previous studies, no aerobic mesophilic bacteria were detected in such samples. Nevertheless, microbial contamination of the resin has been reported in plant protocols. The regeneration treatment, which also mechanically affects the resin material, can cause cracks and crevices in the resin, where microorganisms can grow and persist. In this context, a previous study reported the occurrence of nitrite-forming _Thermus_ species located in ion exchanger columns [51]. These species could not be identified in the regenerate, suggesting that they survive in the resin. No published investigation based on cultural methods could detect growth in hard and thin juice samples [54].