Aquaculture is an economic activity that faces the unavoidable problem of water quality detriment, which is mainly generated by the improper management of production ponds, including inadequate water circulation and aeration, accumulation of undigested food residues, excretion of metabolic by‐products by the cultivated organisms and other. In addition, the increase in suspended organic matter together with the presence and generation of nitrogen compounds can severely affect the physiology of the animal, leading to significant losses in production. Ammonia (NH3), nitrite (NO2) and nitrate (NO3) are toxic in different scales and environmental conditions; therefore, reducing their concentrations in the culture units has paramount relevance. In this regard, bioflocs are an efficient alternative to transform nitrogen compounds into a non‐toxic form, taking advantage of the capabilities of the microbial communities conforming them. Also, nitrogen can be harnessed and incorporated as organic nitrogen, making the biofloc a source of useful natural food for the cultivated organism. The substantial reduction in the rate of water exchange favoured by the biofloc technology (BFT) is a beneficial advantage for both the production systems and the environment, diminishing the risk of introducing pathogens into the pond in parallel with the improvement in the water quality of effluents. Ammonia oxidation is an advantage adding value to the BFT systems and is discussed in this review.

Cheese whey contains about 20% of the total milk protein and has high nutritional and technological value, as well as attractive biological properties. Whey protein represents an important source of bioactive peptides with beneficial effects on health (e.g., antioxidant, antidiabetic, antihypertensive, etc.). Microbiota in cheese whey can hydrolyze proteins and generate bioactive peptides through a fermentation process. The objective of this study was to evaluate the effect of temperature on the fermentation of cheese whey by its native microbiota, and the action of microbial proteolytic activity on whey proteins to release peptides with inhibitory activity of the angiotensin-converting enzyme (ACE). Whey proteins hydrolysis occurred at all incubation temperatures evaluated (32–50 °C), with the major proteolytic effect within the range of 35–42 °C. Minor whey proteins (i.e., Lf, bovine serum albumin (BSA), and IgG) were more susceptible to degradation, while β-lactoglobulin and α-lactalbumin showed major resistance to microbial proteolytic action. Alfa-amino groups increased from 36 to 360–456 µg Gly/mL after 120 h of fermentation. A higher lactic acid production (11.32–13.55 g/L) and lower pH (3.3–3.5) were also observed in the same temperature range (32–42 °C). In addition, ACE-inhibitory activity increased from 22% (unfermented whey) to 60–70% after 120 h of fermentation. These results suggest that the fermentation of cheese whey by its native microbiota represents an attractive process to give value to whey for the production of whey-based beverages or functional foods with potential antihypertensive properties.

Bacterial infections represent the greatest threat for fish culture, especially those causing granulomatous processes. Although there are experimental models used to elucidate the mechanisms of pathogenicity in granulomatous processes, most of these aimed to understand the infection in superior vertebrates like humans; therefore, there is still an urgent need to expand the number of infection models focused on aquaculture. Granulomatous infections are difficult to detect in early stages due to the lack of clinical signs and because these clinical signs have a great similarity to those generated by other pathogenic bacteria. Besides, there is no evidence or reports of granulomatous co-infections in aquaculture environments which is a plausible scenario either in culture systems or in the wild environment; co-infections could interfere with a correct diagnosis of any granulomatous disease, as reported for granulomatous infections in terrestrial species. This revision aims to highlight the state of the art in the knowledge of pathogenic bacteria associated with granulomatosis in fish aquaculture as well as analysing this information.

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.

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