# The Influence of Fermentation Vessels on Yeast Microbiota and Main Parameters of Sauerkraut
## Results and Discussion
### The Influence of the Vessel Used for Fermentation on the Yeast Microbiota of Sauerkraut
The presence of undesirable microorganisms (such as film-forming yeast, _Rhodotorula_, and filamentous fungi) that may negatively affect the product is one of the reasons for producers to abandon the traditional method of obtaining fermented vegetables [22], and the use of anaerobic conditions and starter cultures is increasingly common, as in other industrial fermentation processes, which increases microbiological stability, reduces losses, and improves the quality of the product created [23]. For qualitative analysis of yeast, 36 cultures were isolated, and the obtained isolates were subjected to RAPD-PCR analysis, which allowed the selection of 10 different biotypes. Sequencing of the ITS region and PCR-RFLP analysis led to the classification of isolates into five species (Figure 3; Table 1), with the yeast _D. hansenii_ represented by three different strains, and _Rh. mucilaginousa_ and _W. anomulus_ by two strains each. They were identical to those obtained in the first (preliminary) stage of the study. The isolates also included a representative of one new species of yeast (only in jars), identified as _Clavispora lusitaniae_ (Figure 3; Table 1). During the fermentation of sauerkraut, both in glass jars and stoneware vessels, a large variability in the presence of different strains was found on subsequent days of fermentation. This is a phenomenon typical of spontaneous fermentation, during which successive quantitative and qualitative changes of microorganisms occur, which is related to the presence or absence of oxygen, inhibition by formed products (such as lactic acid, ethyl alcohol, and others), depletion of nutrients, or interactions between different groups of microorganisms [4,12]. The greatest differences in the qualitative composition of yeast concerned the occurrence of representatives of the species _W. anomulus_ only in the stoneware vessels, and the cultures of _Cl. lusitaniae_ only in the jars. Strains that could grow anaerobically grew better in jars, and cultures that preferred a higher oxygen concentration were present in stoneware vessels. Live _W. anomulus_ yeast cells were found in stoneware vessels after the first day of fermentation, and their maximum level was found on the third day, when they constituted 100% of the isolates. In the following days, their number decreased rapidly, and on the seventh day they were no longer detected. The _W. anomulus_ Wa1 strain occurred between the first and third days of fermentation, while the _W. anomulus_ Wa7 strain--between the second and fourth days. The differences in growth were probably related to the changing conditions in the environment between the third and fourth days of fermentation. At this time, the greatest decrease in environmental pH occurred during fermentation in stoneware vessels and an increase in the concentration of lactic and acetic acid (Table 2), as well as a sharp increase in the number of LAB (Figure 4), which may have an antagonistic effect on some yeast cultures [24]. In the first stage of experiments, _W. anomulus_ cultures were also found in the final stage of fermentation (Figure 1), and this was related to the presence of the _W. anomulus_ Wa22 strain, which, as it should be assumed, was not present at the discussed stage of the study. Figure 3: Distribution of yeast strains (%) during Galaxy cabbage fermentation depends on the fermentation vessel. As already mentioned, the yeast _W. anomalous_ is characterized by fully aerobic or weak fermentative metabolism [10]. Therefore, although they are generally associated with various fermentation processes, their development is most often related to the availability of oxygen. _W. anomalous_ is often among the \"film-forming\" yeasts associated with spoilage of beer, wine, and fermented vegetables [25], as well as bakery products [26]. According to [PERSON] and [PERSON] [27], these cultures are relatively resistant to the presence of lactic acid, but sensitive to acetic acid.