Eugenio Geremia

Alongside growing concern about the environmental impacts of the aquaculture production sector, increasing interest is being directed toward sustainable alternatives to traditional protein sources used in aquafeed, such as fish meal and soybean meal. Among these, brewers’ spent grain (BSG), a byproduct of the brewing industry, has recently emerged as an alternative ingredient. BSG is a low-cost, year-round resource that may be well-suited for the circular economy. It contains moderate levels of proteins (15%–27% of dry matter) and appreciable amounts of antioxidant compounds (polyphenols and phenolic acids). Several studies show that BSG can replace up to 50% of traditional protein sources in aquafeed formulations without compromising growth performance. However, BSG has drawbacks, including its high content of antinutritional factors (ANFs) and its relatively low level of essential amino acids. Processing strategies such as hydrolysis and fermentation appear promising for reducing ANFs and enhancing protein availability. Moreover, information on the global impacts of using BSG in aquafeed, either raw or processed, remains limited. A Life Cycle Assessment analysis conducted on two hypothetical diets with 10% or 37% BSG as partial replacements for traditional ingredients reveals that a detailed assessment of environmental impacts across all stages of aquafeed production is essential to support the large-scale adoption of BSG in aquaculture.

Nitrite pollution in aquatic environments, often driven by human activity, can disrupt fish physiology. Nitrite is absorbed by freshwater fish through their gills, leading to internal accumulation and interference with nitric oxide (NO) signaling, redox state, and the oxygen-carrying capacity of blood. The effects of nitrite are concentration-dependent. Although moderate environmental nitrite levels have little impact on oxygen transport, they may still interfere with NO homeostasis and cellular metabolism. We report the effects of 72 h of exposure to 10 μM nitrite on adult zebrafish blood’s O₂-carrying capacity and on muscle mitochondrial activity, metabolism, and redox state. The results show that this environmentally relevant but moderate concentration of nitrite leads to decreases in fish routine oxygen consumption (rMO₂) and spontaneous activity, an increase in blood nitrosyl hemoglobin (HbNO), indicating increased NO production in the blood, accumulation of nitrite in muscle tissue, oxidative stress, and changes in muscle aerobic capacity linked to a rise in mitochondrial efficiency. Parallel to these effects, increases in antioxidant capacity, arginase activity, and urea and lactate levels were observed. Globally, these results are consistent with altered NO homeostasis in the fish body induced by nitrite stress.

Oxidative stress is a key contributor to diabetes-related cognitive decline and is intensified by diabetes distress (DD), the psychological burden of disease management. DD lowers brain levels of nuclear factor erythroid 2-related factor 2 (NRF2), a transcription factor that regulates antioxidant defense. This study examined whether chlorogenic acid (CGA), a polyphenolic NRF2 activator, could counteract oxidative and astroglial dysfunctions in adult zebrafish subjected to chronic unpredictable mild stress (CUMS) combined with dextrose, a model mimicking DD. Zebrafish were treated with CGA (50, 100, or 200 mg/kg), and the levels of NRF2 protein and mRNA, along with its regulator keap1, were quantified. Expression levels of key downstream antioxidant genes (sod1, sod2, catalase, glutathione peroxidase, and glutamate-cysteine ligase catalytic subunit) were assessed alongside glutathione (GSH) content and superoxide dismutase (SOD) and catalase activities. Astroglial integrity was evaluated via glial fibrillary acidic protein (GFAP) levels in the whole brain and stress-sensitive regions. CGA increased total brain NRF2 protein, its mRNA, and those of its downstream effectors. At 200 mg/kg, CGA restored GSH levels, boosted antioxidant enzyme activities, and mitigated DD-associated reductions in GFAP and NRF2 in stress-vulnerable areas. These findings identify NRF2 as a promising target to protect brain health under diabetic conditions.

The food industry widely uses dyes from animal and plant sources, but their discharge into water bodies can harm aquatic animals. Red food dyes increase reactive oxygen species (ROS) production, disrupting redox homeostasis in Artemia franciscana nauplii, although the underlying mechanisms are unclear. In this study, we exposed Artemia franciscana cysts for 48 h to three different red dyes: E124 (synthetic), E120 (animal-based) or Vegan red (plant-based) and evaluated the oxidative metabolism and redox status in the hatched nauplii. Only E120 and VEG increased oxygen consumption. E124 and VEG increased mitochondrial Complex I activity, while all dyes enhanced the activity of Complex III. The levels of reactive oxygen species (ROS) and NADPH oxidase activity were increased by all red dyes. E120 and E124 increased antioxidant enzyme activity to a greater extent than VEG. Additionally, only E120 and E124 increased total antioxidant capacity. Nevertheless, E124 exposure induced redox imbalance (increased lipid and protein oxidative damage). Our data, as a whole, allow us to conclude that red dyes can influence the oxidative capacity and redox state of Artemia franciscana nauplii with more harmful effects in the presence of E124, thus drawing attention to their potentially severe influence on aquatic life.

In recent years, interest in the impact of environmental pollutants on the ecosystem has increased significantly, with particular attention being paid to the relationship between climate change and the aquatic world. This is because increasing pollution is causing fundamental changes to the welfare of animals and the marine ecosystem. A primary focus is on the impact of microplastics (MPs) and nanoplastics (NPs), as evidenced by our bibliometric network analysis (BNA). However, while research is focused on the accumulation of these pollutants in aquatic organisms, their effects on redox homeostasis are still seldom discussed despite the role played by reactive oxygen species and mitochondrial well-being in maintaining an optimal state of health. However, some scientific evidence suggests that the accumulation of MPs and NPs in organisms at the base of the trophic chain can cause a transfer of these substances towards more complex organisms, reaching humans through the consumption of aquatic fauna as food. Therefore, in this review, we have tried to discuss the effects of these substances on oxidative stress in aquatic organisms, even if studies in this regard are still scarce.

Microalgae have received much attention in the last few years. Their use is being extended to different fields of application and technologies, such as food, animal feed, and production of valuable polymers. Additionally, there is interest in using microalgae for removal of nutrients from wastewater. Wastewater treatment with microalgae allows for a reduction in the main chemicals responsible for eutrophication (nitrogen and phosphate), the reduction of organic substrates (by decreasing parameters such as BOD and COD) and the removal of other substances such as heavy metals and pharmaceuticals. By selecting and reviewing 202 articles published in Scopus between 1992 and 2020, some aspects such as the feasibility of microalgae cultivation on wastewater and potential bioremediation have been investigated and evaluated. In this review, particular emphasis was placed on the different types of wastewaters on which the growth of microalgae is possible, the achievable bioremediation and the factors that make large-scale microalgae treatment feasible. The results indicated that the microalgae are able to grow on wastewater and carry out effective bioremediation. Furthermore, single-step treatment with mixotrophic microalgae could represent a valid alternative to conventional processes. The main bottlenecks are the large-scale feasibility and costs associated with biomass harvesting.