Bacterial Diversity and Dynamics during Spontaneous Cheese Whey Fermentation at Different Temperatures

The effect of temperature (32–50 °C) on bacterial dynamics and taxonomic structure was evaluated during spontaneous whey fermentation for lactic acid production. Bacterial plate count in fresh whey (5 log CFU/mL) increased in two orders of magnitude after 60 h of fermentation (7 log CFU/mL), followed by one log reduction after 120 h (6 log CFU/mL) at 37 and 42 °C. Streptococcus and Lactobacillus counts ranged between 5–9 and 5–8 log CFU/mL, respectively. High-throughput sequencing of the 16S rRNA gene (V3-V4 region) used as a taxonomic marker revealed thirteen different bacterial phyla. Actinobacteria, Bacteroidetes, Firmicutes, and Proteobacteria were detected in all fermentation treatments (32–50 °C, 0–120 h), where Firmicutes was the predominant phylum. Bacterial diversity included more than 150 bacterial genera with predominant lactic acid bacteria (belonging to Firmicutes) such as Lactobacillus, Lactococcus, Streptococcus, and Tetragenococcus. At the species level, fresh whey presented 61 predominant species (relative abundance > 0.05%); however, only 57.4% of these resisted the fermentation conditions (most of them belonging to lactic acid bacteria genera). Tetragenococcus halophilus, Lactococcus lactis, and Enterococcus casseliflavus were the predominant bacteria found in all treatments. Temperatures between 37–42 °C were more favorable for lactic acid production and could be considered appropriate conditions for fermented whey production and for the standardization of some artisanal cheese-making processes requiring acid whey addition for milk coagulation. The diversity of native beneficial bacteria found in fresh whey offers attractive technological characteristics, and their fermentative capacity would represent a biotechnological option to add value to cheese whey.