## 3 Results and Discussion
### Batch Fermentation with Strains in Suspension and Immobilized  
3.1 Batch Fermentation with Strains in Suspension Using _Enterococcus faecalis_ and _Kluyveromyces lactis_  
Figure 1 shows the fermentation with _Enterococcus faecalis_ in suspension using the deproteinized cheese whey (ESI) and cheese whey without deproteinized (ES2). It was observed that there were differences in the lactic acid yield using both cheese whey samples and, in both cases, when the pH decreased, there was a greater generation of lactic acid. With the deproteinized cheese whey, the generation of lactic acid was low given that its pH tends toward neutrality, and the presence of fats, proteins, and other components of the cheese whey probably influenced the behavior of the strains and therefore the production of lactic acid. This behavior was clearly observed, since the maximum value of lactic acid obtained was 13.09 \(\pm\) 1.54 g/L, which occurred after 48 h of fermentation with the lowest pH value (4.90 \(\pm\) 0.16) with the deproteinized cheese whey. However, raising the pH inhibited the generation of lactic acid. Using _Enterococcus_ isolated from cheese whey to obtain lactic acid has been demonstrated in another study that achieved up to 15.93 \(\pm\) 0.13 g/L and 15.43 \(\pm\) 0.03 g/L levels of lactic acid using proteinized cheese whey and nutritional additives, respectively [9]. Figure 2 shows the lactose consumption against the production of lactic acid. It was observed that when using the deproteinized cheese whey (ESI), there was a greater reduction in the lactose concentration, reaching up to 2.80 \(\pm\) 0.0 \({}^{\circ}\)Brix with an acidity of 13.09 \(\pm\) 1.54 g/L of lactic acid, starting from 8.10 \(\pm\) 0.0 \({}^{\circ}\)Brix. Meanwhile, with the proteinized cheese whey (ES2), although there was a decrease in lactose, there was no generation of lactic acid. This was due to the pH medium, which was in the neutrophil range, which has been seen to disfavor the production of lactic acid. In addition, it contained other components that may have affected the assimilation of lactose, such as proteins and fats. This behavior of _Enterococcus faecalis_ is similar to other works, since it has been shown that with a pH of between 4 and 5.79, good yields of lactic acid were obtained [11]. In another study at pH 5, a high yield of lactic acid was also obtained using _Enterococcus faecalis_ and _Enterococcus hirae_ from cheese whey [9]. However, there is another study whose \begin{table}
\begin{tabular}{c c c c c} \hline
**Salinity (\%)** & _E. faecalis_ & **Media Blank** & _K. lactis_ & **Media Blank** \\ \hline
1 & +++ & \(-\) & +++ & \(-\) \\
2 & +++ & \(-\) & +++ & \(-\) \\
4 & +++ & \(-\) & +++ & \(-\) \\
6 & \(-\) & \(-\) & ++ & \(-\) \\
8 & \(-\) & \(-\) & + & \(-\) \\
10 & \(-\) & \(-\) & +\(-\) & \(-\) \\
11 & \(-\) & \(-\) & +\(-\) & \(-\) \\
12 & \(-\) & \(-\) & +\(-\) & \(-\) \\
13 & \(-\) & \(-\) & \(-\) & \(-\) \\ \hline
**pH** & _E. faecalis_ & **Media Blank** & _K. lactis_ & **Media Blank** \\ \hline
4 & \(-\) & \(-\) & \(+\)\(-\) & \(-\) \\
7 & ++++ & \(-\) & +++ & \(-\) \\
9 & ++++ & \(-\) & +++ & \(-\) \\ \hline \end{tabular} Note. – There was no growth, \(-\)\(\rightarrow\) little growth, \(+\)\(-\) slight growth, \(+\) growth, \(++\) regular growth, and \(++\) good growth.  
\end{table} 
Table 4: _Cont._highest production of lactic acid (4.5 mg/mL) was determined at pH 3.5 and 37 \({}^{\circ}\)C in MRS broth using _Enterococcus_ isolated from the rectal area of rats [10]. Additionally, a strain of _Enterococcus faecalis_ isolated from food remains produced 19.5 g/L of lactic acid at 37 \({}^{\circ}\)C and at a pH of between 6 and 8, achieving the highest production at pH 7 [17]. These results show that _Enterococcus_ can produce lactic acid but under certain conditions, depending on the source of isolation.