## 3 Results and Discussion
### Batch Fermentation with Strains in Suspension and Immobilized
It should be noted, as shown in Figure 6, that regarding the lactose consumption with the immobilized _Enterococcus faecalis_, if the data on the lactose consumption in both cases are taken, there was a greater level of consumption when using the proteinized cheese whey (from 6 to 2.67 \({}^{\circ}\)Bx) than with the deproteinized cheese whey (from 5.07 to 2.47 \({}^{\circ}\)Bx). This was probably due to the pH medium, which was not favorable for an optimal environment for further lactose metabolism to occur. If we examine the amount of lactic acid obtained with the immobilized _Enterococcus faecalis_ and only with the deproteinized cheese whey as a substrate, it had the highest lactic acid yield compared to the suspended _Enterococcus faecalis_ in both the proteinized and deproteinized cheese whey. This behavior was also observed with the _Enterococcus_ strains isolated from cheese whey, which obtained a level of 41 \(\pm\) 0.4 g/L at 96 h of incubation when using the encapsulated _Enterococcus_ compared to using them without encapsulation, where they obtained 16.27 \(\pm\) 0.09 g/L [9]. Therefore, it can be inferred that the isolated strain of _Enterococcus faecalis_ generated a greater production of lactic acid using the immobilized strains and deproteinized cheese whey. Figure 7 shows the production of lactic acid using the immobilized _Kluyveromyces lactis_ and using the deproteinized cheese whey (KI1) and proteinized cheese whey (KI2). Like the _Enterococcus faecalis_ strain, when using the immobilized _Kluyveromyces lactis_, the highest generation of lactic acid (35.70 \(\pm\) 0.15 g/L) was obtained when the pH decreased and when  
Figure 5: Lactic acid yield (g/L) of _Enterococcus faecalis_ and its pH variation during the cheese whey fermentation. the deproteinized cheese whey was used, while when the pH increased and the proteinized cheese whey was used, the lactic acid generated was quite limited. Therefore, it is corroborated that an acidic pH favored the metabolism of lactose and the production of lactic acid using the _Kluyveromyces lactis_, since at pH 3.64, it obtained the highest value of lactic acid, unlike _Enterococcus faecalis_, where the pH tended to become more acidic and the production of lactic acid was interrupted. This advantage is not only observed over _Enterococcus_ but also over other strains like _Lactobacillus casei_, _Enterococcus lactis_, _Enterococcus camelliae_, and _Weissella paramsenteroi_, where at pH 4, the least generation of lactic acid occurred, at pH 5, it increased and rose to its maximum at pH 6 and 7, but at pH 8, it decreased again when using the deproteinized cheese whey, with _Lactobacillus casei_ being the one that generated the highest lactic acid content, generating 44.25 g/L after 10 h of fermentation [11]. Figure 8 shows the lactose consumption of the immobilized _Kluyveromyces lactis_, demonstrating higher amounts for the deproteinized cheese whey (KI1), achieving up to 2.07 \({}^{\circ}\)Brix, compared to using the proteinized cheese whey (KI2). Hence, when we used the  
Figure 6: Lactic acid yield (g/L) of _Enterococcus faecalis_ and its lactose consumption during the cheese whey fermentation. Figure 7: Lactic acid yield (g/L) of _Kluyveromyces lactis_ and its pH variation during the cheese whey fermentation. proteinized cheese whey without any supplements (KI2), the lactose metabolism and its uptake were affected, despite the fact that the pH values were lower than 5. These results allow us to conclude that if we use suspended _Kluyveromyces lactis_, we have to use proteinized cheese whey with nutritional additives, but for deproteinized cheese whey, no other additives are required, and the _Kluyveromyces lactis_ strain must be immobilized, with the latter being more favorable since it would reduce costs.