## 3 Results and Discussion
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Nr.** & **Name Sample** & **Microorganisms** & **MSP Score * \\ \hline \hline \multirow{8}{*}{\(1\)} & \multicolumn{2}{c}{Part 1} \\ \cline{3-4}  & & _Pseudomonas_ & 2.21 \\  & & _fluorescens_ & 2.18 \\  & \(\alpha\)–serum & _Bacillus cereus_ & 2.32 \\  & light fraction & _Serratia marcescens_ & 2.08 \\  & & _Escherichia coli_ & 2.36 \\  & & _Microoccus luteus_ & 2.19 \\  & & _Staphylococcus aureus_ & 2.03 \\ \cline{2-4}  & \(\alpha\)–serum heavy fraction & _Microoccus luteus_ & 2.03 \\ \cline{2-4}  & & _Pseudomonas_ & 2.14 \\  & & _fluorescens_ & 2.23 \\  & \(\beta\)-serum & _Lactococcus raffinolactis_ & 2.45 \\  & light fraction & _Serratia marcescens_ & 2.07 \\  & & _Microoccus luteus_ & 2.06 \\  & & _Escherichia coli_ & 2.06 \\ \cline{2-4}  & \(\beta\)–serum & _Microoccus luteus_ & 2.29 \\  & heavy fraction & _Staphylococcus aureus_ & 2.32 \\ \cline{2-4}  & \(\Delta\)MF ** & \multicolumn{2}{c}{no identified microorganisms} \\ \hline \multicolumn{4}{c}{Part 2} \\ \hline \multirow{8}{*}{\(2\)} & \(\alpha\)–serum & _Microoccus luteus_ & 2.20 \\  & light fraction & _Serratia marcescens_ & 2.37 \\ \cline{2-4}  & \(\beta\)–serum & _Microoccus luteus_ & 2.12 \\  & heavy fraction & _Staphylococcus aureus_ & 2.21 \\  & & _Lactococcus raffinolactis_ & 2.35 \\  & & _Escherichia coli_ & 2.41 \\ \cline{2-4}  & \(\beta\)–serum & _Serratia marcescens_ & 2.40 \\  & light fraction & _Microoccus luteus_ & 2.27 \\ \cline{2-4}  & \(\beta\)–serum & _Pseudomonas_ & 2.26 \\  & heavy fraction & _Staphylococcus aureus_ & 2.19 \\ \cline{2-4}  & \(\Delta\)MF ** & \multicolumn{2}{c}{no identified microorganisms} \\ \hline \multicolumn{4}{c}{Part 3} \\ \hline \multirow{8}{*}{\(3\)} & \(\alpha\)–serum & _Microococcus luteus_ & 2.22 \\  & light fraction & _Escherichia coli_ & 2.36 \\ \cline{2-4}  & \(\alpha\)–serum heavy fraction & _Pseudomonas_ & 2.20 \\  & & _fluorescens_ & 2.16 \\  & & _Lactococcus raffinolactis_ & 2.36 \\ \cline{2-4}  & \(\beta\)–serum & _Pseudomonas_ & 2.36 \\  & light fraction & _Lactococcus raffinolactis_ & 2.14 \\ \cline{2-4}  & \(\beta\)–serum & _Lactococcus raffinolactis_ & 2.02 \\  & heavy fraction & _Microoccus luteus_ & 2.26 \\ \cline{2-4}  & \(\Delta\)MF ** & \multicolumn{2}{c}{no identified microorganisms} \\ \hline \hline \end{tabular}  
* Log score >2.00—secure genus identification, probable species identification. ** Anhydrous milk fat.  
\end{table} 
Table 2: List of identified microorganisms in buttermilk fractions and anhydrous milk fat with the MALDI-ToF MS technique. Figure 2 shows the presence of fatty acids among all the tested samples. Three compounds were the most predominant, namely butanoic acid (butyric acid), decanoic acid (capric acid), and hexadecanoic acid (palmitic acid). Hexanoic acid (caproic acid) was a fatty acid found only once in the sample of AMF-2. A study by [PERSON] et al. [29] identified free fatty acids (FFAs), including butyric acid, as a component of milk that can induce biofilm formation by microorganisms present in milk. They observed that _Bacillus_ cells were in close proximity to milk fat globules. However, not only _Bacillus_ sp. bacteria can form biofilm but also _Escherichia coli_ and _Staphylococcus aureus_, as well as lactic acid bacteria (LAB) [30; 31; 32; 33]. Consequently, the accumulation of the aforementioned FFAs adduces to the hydrolysis of milk fat, a process referred to as lipolysis [34; 35]. This process can occur through enzymatic activity or spontaneously during milk production [36]. Many bacteria of the genus _Bacillus_ produce lipases capable of lipolyzing milk fat, some of which retain activity even after pasteurization [37; 38]. Therefore, because _Bacillus_ bacteria actively lipolyze milk fat, when they are present in milk, they deplete its milk fat level. A similar relationship is observed for our microbiological analyses, as they revealed the presence of various bacterial species, including _E. coli_, _Serratia liquefaciens_, _L. lactis_, and _Microoccus luteus_ (Table 2).