###### Abstract
Lactic acid bacteria (LAB) are Gram-positive bacteria, with cocci and/or coccobacillus, and they are catalase-negative and usually aerotolerant; that is, they can be strict anaerobes or microaerobes, acid-tolerant, and non-spore-forming [7;8]. From them, _Lactobacillus_, _Streptococcus_, and _Enterococcus_ are the most studied for lactic acid production, with the most abundant strain being the genus _Lactobacillus_. However, _Enterococcus_ are Gram-positive bacteria, cocci, and facultative anaerobes [9] that are clustered in short chains, pairs, or individual cocci; they are considered some of the producers of lactic acid and are homofermentative, and they have been isolated from different human, animal, and fermented food sources [10]. Additionally, they are also considered among the alkaliophilic LAB that produce LA at high pH values between 7 and 11.5 [6]. _Enterococcus_ even generate bacteriocins or antimicrobial peptides, and it has been seen that they also have immunomodulatory properties [10]. However, they are also associated with opportunistic infections such as those in the central nervous system, urinary tract, endocarditis, and abdomen, but since they do not have strong virulent factors or toxins, their limited use is sometimes tolerated in the food industry [7;10]. Regarding the production of lactic acid, _Enterococcus faecalis_ AG5 has been shown to be used for the production of lactic acid [10] in addition to _Enterococcus lactis_, _Enterococcus__amelliae_, and _Weissella__parameters_[11]. Regarding yeasts, they have an advantage over LAB in that at low pH, they are very stable; accordingly, with yeasts, we can avoid using neutralizing agents [6]. Among yeasts, there is _Kluyveromyces lactis_, a yeast that can carry out fermentation under anoxic and aerobic conditions; additionally, it is capable of the consumption of lactose [12] and it is usually employed to produce proteins [13], organic acids, and ethanol [12]. _Kluyveromyces lactis_ has been seen to generate high-cell-density lactic acid by using low-cost carbon sources such as lactose and cheese whey and, due to its ease of genetic manipulation, it has also been modified to produce biopolymers such as hyaluronic acid [14] and to increase its production of lactic acid [6]. In the fermentation process, immobilized or suspended cells can be used. The immobilization process is known to allow for increasing cell retention and cell density in bioreactors, to diminish the microbial latency phase, to improve its tolerance at high sugar concentrations, to have a better pH control, and to generate greater productivity because the purification process is easier than fermentation with suspended cells. The fermentation can be carried out with immobilized or suspended cells. The immobilization of microorganisms has the following advantages: it allows for increasing cell retention and density in bioreactors, the microbial latency phase is diminished, it has a high tolerance at sugar concentrations, the pH control is better, and it has more productivity due to the purification processes being easier [9]. To immobilize LAB strains, sodium alginate, calcium chloride, polyethylene amine, and plastics have been used, and they acted as supports for the production of lactic acid that was used in batch fermentations for more than 126 days with _Enterococcus hirea_[9]. Additionally, this advantage has also been observed when immobilized strains of _Kluyveromyces lactis_ generated an increase in lactose removal efficiency that was 3.4 times greater than when they were used as suspended cells [15]. Therefore, in this research, it was proposed to obtain lactic acid through the batch fermentation of cheese whey with its native strains (_Kluyveromyces lactis_ and _Enterococcus faecalis_) and to determine its influence on the production and characteristics of lactic acid.