## 2 Materials and Methods
### Preparations of Fermented Plant Extract (FPE) and Plant Extract (PE)  
#### 2.2.1 Preparations of FPE  
New fermented plant extracts (FPEs) were obtained by the fermentation of clove buds. In our study, as a raw material to produce lactic acid, we used beet molasses, which is a waste product of the sugar industry. We determined the total content of 6-carbon sugars(Brix) present in the molasses using a refracometer method (KRUSS Optronic DR301-95, A. Kruss Optronic GmbH, Hamburg, Germany). The buds fermentation process used beet molasses, which eliminated the need for additional mineral salts in the form of nitrates or ammonium salts, chlorides, and potassium phosphate [34]. Preliminary tests verified that the nitrogen and phosphorus contained in molasses were sufficient for proper fermentation. For this purpose, molasses aqueous solutions were fermented with 3.20% mixed inoculum (the amount of which was determined based on our previous studies), but without the presence of mineral salts [3]. Preliminary studies have shown that beet molasses containing up to 2.0% total nitrogen has sufficient amounts of essential nitrogen to produce lactic acid [24]. This nitrogen is mainly represented by amino acids such as glutamic acid, aspartic acid, and alanine, and, to a small extent, also by ammonium salts. The phosphorus content (about 0.2%) in molasses also proved sufficient for fermentation [29; 30]. Adequate growth of lactic acid was observed in all molasses solutions, to a similar extent to fermentations carried out in the presence of certified care molasses requiring the additional use of mineral salts such as ammonium sulphate (0.64%), calcium chloride, and potassium dihydrogen phosphate (0.32%) [3]. Next, the fermentation of the buds was carried out using lactic acid bacteria. The fermentation was carried out until the maximum level of LA was reached, the concentration of which was controlled by the GC-MS method. The level of total polyphenol content (TPC) was also monitored during fermentation. In addition to the matrix of the plant material used, the bioavailability of phenolic compounds is also affected by the type of LAB strain used. Therefore, fermentation of buds was carried out using 6 individual strains of LAB: _L. reuteri MI_0168, L. salivarius LY_0652, L. brevis LY_1120, L. acidophilus MI-0078, L. rhamn-sus MI-0272, and L. plantarum MI-0102._  
We prepared the inoculum according to a previously used procedure [3]. The subsequent raw materials were presented into a 500 mL conical flask: beet molasses (the amount of which was controlled depending on the process parameter under study while maintaining an initial sugar content of 1.0-5.0%), distilled water, plant material constituting clove buds (the amount of which was controlled depending on the process parameter under study while maintaining a content of 1.0-7.0%), and inoculum (in an amount of 3.20%). The content of inoculum in the fermentation medium was determined earlier, as a result of preliminary studies [3]. The contents of the flask were agitated until the molasses was completely dissolved; subsequently, the fermentation process commenced (at a temperature of 37.5 \({}^{\circ}\)C) for an appropriate time. During the fermentation process, samples were collected and examined for lactic acid content (whose concentration was determined by GC-MS) and polyphenols (whose levels were determined by the spectrophotometric method using the Folin-Ciocalteu technique). The fermentation was carried out until the maximum level of lactic acid was reached. The highest content of LA was observed on the 9-10 days (depending on the process parameter under study) of fermentation, and continuing the process had the effect of decreasing LA concentration. Two independent experiments carried out the fermentation process.