# 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
They carry out the hydrogenation of fructose using NADH- and NADPH-dependent enzymes [45]. _Leuconstoc_ bacteria are heterofermatative lactic acid bacteria, facultatively anaerobic [46]. With a greater presence of oxygen (stonewase vessels), these bacteria may develop less strongly, and aerobic conditions may also favor the development of microbiota, which can use mannitol as a carbon source for its growth. Such microorganisms include yeast of the _Rhodorula_ genus [47]. Glycerol was not detected in samples up to the third day of fermentation (Table 3). In the following days, the amount of this polyol increased, reaching the maximum level on the seventh (jars) or tenth day of fermentation (stonewase). Then, the level of this compound decreased. Glycerol formation is usually associated with the presence of fungal microorganisms and _Saccharomyces_es and non-_Saccharomyces_es yeast [48]. Generally, glycerol production by prokaryotic microorganisms has not been studied as well as that by yeasts. Similar to yeasts, LAB can use enzymes of the glycerol kinase pathway for glycerol production. A process of glycerol production similar to that in yeasts may occur in LAB, also under stress conditions [49]. In the LAB group, various _Lb. plantarum_ strains are most often mentioned as glycerol producers. Anoxic glycerol fermentation by various microbial species may lead to the production of a variety of other valuable compounds, such as 1,3-propanediol, 1,2-propanediol, propionic acid, succinic acid, ethanol, n-butanol, and reuterin [50]. Free amino nitrogen is very important for developing microorganisms, and it can also be a precursor to a whole range of compounds affecting the sensory properties of fermented products [51]. Changes in the FAN content during fermentation are presented in Table 3. The analysis showed no statistically significant impact of the vessel used for fermentation on its level. Maximum levels of amino nitrogen were detected in the final phase of fermentation, from the seventh day. The FAN content was influenced not only by amino acids released from the raw material, but also by those produced from dead microbial cells. High cell mortality, especially in spontaneous processes, at the end of fermentation may result in an increase in the content of the discussed group of compounds [52]. Their  
\begin{table} \begin{tabular}{l l l l l l l l l l l l} \hline \hline  & **Vessel/Day** & **0** & **1** & **2** & **3** & **4** & **7** & **10** & **14** & **SEM 1** & **Sig. 2** \\ \hline FAN & Glass & 69.6 ab & 59.4 a & 66.7 a & 58.5 a & 61.4 a & 111.2 bcd & 124.6 cd & 137.0 d & 8.4 & *** \\  & Stonewase & 69.6 ab & 61.3 a & 61.6 a & 79.6 ab & 85.1 abc & 136.4 d & 138.6 d & 139.4 d & 7.0 & \\ \hline Total sugars & Glass & 2.98 ab & 4.52 cde & 4.20 bcd & 2.77 ab & 3.17 ab & 5.77 e & 5.65 e & 5.15 de & 0.18 & *** \\  & Stonewase & 2.98 ab & 2.88 ab & 3.01 ab & 2.53 a & 2.89 ab & 3.23 abc & 2.98 ab & **3.31 abc** & 0.24 & \\ \hline \multirow{2}{*}{Reductive sugars} & Glass & 1.91 cd & 3.57 h & 3.78 h & 1.26 a & 2.63 g & 5.18 & 5.60 k & 4.27 l & 0.10 & *** \\  & Stonewase & 1.91 cd & 1.02 a & 1.60 b & 1.78 bc & 2.45 fg & 2.65 g & 2.14 e & 2.21 f & 0.30 & \\ \hline Glucose & Glass & 1.36 b & 0.84 a & 1.18 ab & 0.91 a & 0.92 a & 2.29 c & 2.06 & 2.23 c & 0.12 & *** \\  & Stonewase & 1.36 b & 1.39 b & 1.41 b & 0.90 a & 0.86 a & 6.60 & 3.34 d & 0.89 a & 0.39 & \\ \hline Frutcose & Glass & 1.39 e & 0.37 b & 0.03 a & 0.71 d & 0.07 a & 0.71 d & 0.62 cd & 0.51 bcd & 0.10 & *** \\  & Stonewase & 1.39 e & 0.31 b & 0.46 bc & 0.71 d & 0.00 a & 0.00 a & 0.00 a & 0.00 a & 0.09 & \\ \hline Glycerol & Glass & 0.00 a & 0.00 a & 0.00 a & 0.10 a & 0.67 c & 1.78 f & 1.51 e & 1.03 d & 0.15 & *** \\  & Stonewase & 0.00 a & 0.00 a & 0.00 a & 0.00 a & 0.24 b & 1.48 c & **1.58 e** & 1.45 e & 0.14 & \\ \hline Mannitol & Glass & 1.70 b & 2.04 bc & 2.59 c & 1.24 b & 2.42 c & 6.80 f & 5.24 e & 4.42 d & 0.18 & *** \\  & Stonewase & 1.70 b & 2.60 e & 2.52 c & 2.45 c & 1.70 b & 0.67 a & 0.52 a & 0.73 a & 0.37 & \\ \hline \hline \end{tabular}