## 3 Results and Discussion
### Enzymatic Activity  
The API ZYM tests used for the analysis of the _L. lactis_ A1-A26 strains showed three profiles of enzymatic activity, with three enzymes exhibiting positive activities: leucine arylamidase was observed in two profiles and acid phosphatase and naphthol-AS-Bl-phosphohydrolase were observed in all profiles. However, most enzymes showed no or very weak activity (Table 3). The enzymatic activity of microbes is an important factor for the safety of probiotics; therefore, it is important to determine enzymatic activities of, e.g., lipase, esterase, and \(\beta\)-glucuronidase. The studied strains were found to have no activity of these enzymes, or this activity was weak. Similar observations were reported by [PERSON] et al. [5]. [PERSON] et al. [8] reported the ability of _Lactococcus_ isolates to produce esterases with low-medium activities. Isolates obtained by [PERSON] et al. [32] showed other activities, e.g., strong valine, cystine arylamidase, N-acetyl-\(\beta\)-glucosaminidase, and \(\alpha\)-mannosidase activities. In a study conducted by [PERSON] et al. [15], lactococci exhibited a different profile, as they produced leucine arylamidase, phosphatase, naphthol-AS-Bl-phosphohydrolase, and \(\alpha\)- and \(\beta\)-glucosidase, while _L. lactis_ IDCC 2301 obtained by [PERSON] et al. [13] differed from above strains in that they produced \(\alpha\)-chymotrypsin but not \(\alpha\)-glucosidase.  
It is worth mentioning that the enzyme leucine arylamidase catalyses the removal of an N-terminal leucine from arylamides or p-nitroanilides [33], which is an important technological trait of strains intended to be used as starters in cheese manufacture to ensure the development of desirable flavours [34]. On the other hand, the lack of \(\beta\)-glucuronidase converting precarcinogens into proximal carcinogens and stimulating colonic cancer or included in the formation of toxic steroids (oestrogen) is an advantage of these strains as potential dairy cultures [13; 14]. Therefore, the two A13 and A14 strains may be candidates as probiotic starters in the dairy industry.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Enzyme**} & \multicolumn{4}{c}{**Isolate**} \\ \cline{2-4}  & **A1, A3, A4, A7, A8, A10, A11, A13, A14,** & **A6, A19, A24** & **A2, A5, A9, A12,** \\  & **A16, A17, A18, A20, A22, A23, A25, A26** & **A6, A19, A24** & **A15, A21** \\ \hline Alkaline phosphatase & 1 & 0 & 2 \\ Esterase (C4) & 2 & 0 & 1 \\ Esterase lipase (C8) & 0 & 1 & 0 \\ Lipase (C14) & 1 & 0 & 1 \\ Leucine arylamidase & 3 & 4 & 2 \\ Valine arylamidase & 1 & 1 & 0 \\ Cystine arylamidase & 0 & 1 & 0 \\ Trypsin & 0 & 0 & 0 \\ \(\alpha\)-Chymotrypsin & 1 & 0 & 1 \\ Acid phosphatase & 5 & 4 & 5 \\ Naphthol-AS-Bl-phosphohydrolase & 2 & 2 & 2 \\ \(\alpha\)-Galacosidase & 0 & 0 & 0 \\ \(\beta\)-Galacosidase & 0 & 0 & 0 \\ \(\beta\)-Glucuronidase & 0 & 0 & 0 \\ \(\alpha\)-Glucosidase & 0 & 0 & 0 \\ N-acetyl-\(\beta\)-glucosidaseaminidase & 0 & 0 & 0 \\ \(\alpha\)-Mannosidase & 0 & 0 & 0 \\ \(\alpha\)-Fucosidase & 0 & 0 & 0 \\ \hline \hline \end{tabular}
\end{table}
Table 3: Enzyme activities of the _L. lactis_ strains isolated from cow milk determined by the API-ZYM system.