# The Influence of Fermentation Vessels on Yeast Microbiota and Main Parameters of Sauerkraut
## Results and Discussion  
The Yeast Microbiota during Fermentation in Stoneware Vessels of Cabbages of Different Varieties--Preliminary Studies  
The appropriate vessel used during fermentation plays an important role, as it allows the anaerobic conditions necessary for the process to be maintained, affecting the microbiota. In Poland, traditionally, stoneware vessels with pressure stones are used for sauerkraut fermentation, to prevent shredded cabbage from rising above the brine level, which may result in the development of undesirable microorganisms, such as molds or yeasts [3]. Stoneware is made from clay, kaolin, feldspar, and silica, and is characterized by relatively high porosity with a pore size of around 0.04 \(\upmu\)m and oxygen permeability of 5 mg/liter/year [9]. Considering that the vessel is usually covered with plastic foil, it creates microaerobic conditions inside, enabling the growth of spoilage microorganisms with aerobic metabolism. In the first (preliminary) stage of the described research, we qualitatively analyzed the yeast microbiota present during the fermentation of five different varieties of cabbage (Galaxy, Kilaton, Kronos, Zielonor, and Furious) in stoneware vessels. Due to the lack of thematically similar research articles, the results were compared with those from our earlier studies that used similar experimental conditions but different fermentation vessels (glass jars). During the experiments, 170 yeast isolates were obtained from fermenting sauerkraut of various varieties, showing the morphological diversity of the colonies formed. Analysis of isolates by RAPD-PCR using the M13 primer showed similarity of some electrophoretic patterns, despite obtaining isolates from different cabbage varieties. This proves that the composition of the yeast microbiota on the surface of cabbage leaves is qualitatively similar and at different times during the process, typical of the plant species rather than the variety. Thirty-two cultures (biotypes) with different patterns of bands on the resulting gels were selected for identification by PCR-RFLP reaction and Sanger sequencing of the ITS region (Table 1). The presence of 11 strains classified into 5 yeast species was found. Three of them--_Deharyomyces hansenii_, _Rhodotorula mucilaginousa_, and _Pichia fermentatus_--were identified in our previous studies, in which glass jars were used for fermentation and the entire process took place in anaerobic conditions [5]. It should, therefore, be assumed that these are microorganisms that develop in sauerkraut, regardless of the conditions during fermentation. The four identified _D. hansenii_ strains developed during the initial fermentation period (up to day 4), while the other two species occurred during the first two days of fermentation and then at its end. The remaining two yeast species found--_Wickerhamomyces anomalus_ and _Torulospora delbrueckii_--were not detected during our previous studies. Their presence during cabbage fermentation, regardless of the variety used, proves that the conditions, i.e., the availability of oxygen, contributed to their development in an amount that enabled their detection. The experiments showed the presence of three different strains of yeast of the species _W. anomalous_ (Table 1). _W. anomalous_ is able to grow abundantly in different fermented foods due to its fully aerobic or weakly fermentative metabolism [10]. This may explain why these yeasts were found during the fermentation of sauerkraut in stonewear vessels and were not present during its production in anaerobic conditions. According to [PERSON] et al. [11], it can grow under extreme environmental stress conditions, such as low and high pH, low water activity, and high osmotic pressure. Due to these characteristics, this yeast can be a spoilage organism, for instance, in silage. Moreover, together with other species (including _S. cerevisiae, R. rubra_, and _D. hansenii_), _W. anomalous_ was found as a natural microbiota of traditional Chinese sauerkraut [12]. _W.