# 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
Reducing the level of acetic acid in the fermented vegetable may mean limiting the growth of the microbiota synthesizing this substance, and on the other hand, degradation/conversion of this compound to other components. In the study by [PERSON] et al. [38], the analyzed microorganisms were able to assimilate acetic acid after a prolonged lag phase. The analysis results showed the conversion of acetic acid to acetyl-CoA by acetyl-CoA synthetase using the TCA cycle and the glyoxylate cycle, enabling bacteria to grow on acetic acid after the depletion of other carbon sources. Similar concentrations of oxalic acid were detected in sauerkraut regardless of the vessel used for fermentation. [PERSON] et al. [39] reported that the presence of this compound has a good effect on the storage of cabbage before fermentation due to its antioxidant properties and inhibitory effect on the spoilage of the raw vegetable. The above-mentioned publication proves that the concentration of this acid decreases as the storage temperature increases. It should be assumed that during fermentation, this compound is released into the environment, and the lactic acid bacteria present in it use this compound. The reduction in oxalic acid content was possibly due to the oxalate-degrading activity of lactic acid bacteria achieved by the transportation of oxalate by permease into the cells [40]. Succinic acid is one of the natural acids found in foods, such as broccoli, rhubarb, sugar beets, fresh meat extracts, various cheeses, and sauerkraut. Succinic acid is also one of the most important acids found in cabbage juice. During fermentation, it is partially metabolized by microorganisms, and sauerkraut juice contains about 50% of its initial content [41]. During sauerkraut fermentation, regardless of the vessel in which the process was carried out, a gradual decrease in the amount of succinic acid was observed (Table 2). However, the intensity of its level reduction was different--significantly higher in jars than in stoneware vessels. An inverse correlation was found between the number of lactic acid bacteria and the concentration of succinic acid. Sauerkraut obtained in glass jars contained more than two times less succinic acid than that produced in stoneware vessels. The Influence of the Vessel Used for Fermentation on the Selected Sugars, Polyols, FAN Level, and Sensory Profile of Sauerkraut  
The DNS method was used to analyze changes in the concentration of total and reducing sugars during fermentation [6]. Most of the sugars during fermentation were reducing sugars, such as glucose and fructose (Table 3). Chromatographic analysis (HPLC) of the content of these sugars during sauerkraut fermentation showed that the glucose level, regardless of the fermentation vessel used, gradually increased, while fructose decreased to zero in the case of stoneware vessels. White cabbage contains approximately 25 g/100 g DW of polysaccharides, constituting dietary fiber. They are mostly made of glucose [42]. During fermentation, the enzymatic activity of the microorganisms present causes the gradual release of simple sugars, which are used for growth and cellular metabolism [43]. Larger amounts of available sugars in the jars could have influenced the production of higher concentrations of lactic acid (Table 2). Fructose is present mainly In free, soluble form and is quickly metabolized by microorganisms. One of the products of its metabolism is mannitol [44]. By the fourth day of fermentation, the mannitol level was similar in all samples (Table 3), ranging from 17.0 to 25.9 g/kg. In the following days, its amount decreased more than three-fold in stonewase vessels, while in jars it more than doubled. This phenomenon may be related to changes in the composition of the current microbiota responsible for the ongoing transformations, both yeast and bacterial. According to [PERSON] et al. [44], _Leuconstoc_ bacteria, present during cabbage fermentation, are responsible for the production of mannitol.