The production of lactic acid (HLa) has attracted a great deal of attention due to its widespread applications in food, chemical, cosmetic, plastic and pharmaceutical industries. HLa is produced from glucose derived from starchy materials, which impacts its production cost and competes with food supply. Cheese whey is a by-product of cheese manufacturing, which production is estimated as 9-fold the cheese production. Availability of lactose and other essential nutrients for the growth of microorganisms makes whey a potent raw material for the production of different bio-products. The aim of this work is to study the production of HLa using cheese whey as substrate and mixed microbial communities. Batch experiments were performed to evaluate the influence of initial and operating pH and the ratio substrate/inoculum on lactate production using the central composite design (CCD). According to the CCD, 11 conditions were evaluated, and the central condition in triplicate. Two sets of experiments were performed: with or without the addition of buffer. Samples were taken at 24, 48, 72 and 120 hours. The total reducing sugars and HLa concentration were determined. The microbial communities of the samples with the highest HLa production from each set of experiments were analyzed by 16S rRNA gene massive sequence analysis. In the set without buffer the maximum production of HLa occurred in the condition with pH 7 and 25% of inoculum (condition 4) and was 13 g/L. In the set with buffer, the maximum HLa production was 20.1 g/L, corresponding to condition with pH 7 and 5% of inoculum (condition 3). While the sample taken from the condition 4 was highly enriched in lactic acid bacteria from the genera Streptococcus and Lactococcus, the sample taken from condition 3 was enriched in Lactococcus and Klebsiella, which is consistent with the high HLa production obtained.
