Modification of the chemically induced inflammation assay reveals the Janus face of a phenol rich fulvic acid

Inflammation is an essential process as a reaction towards infections or wounding. Exposure to hazardous environmental pollutants can lead to chronic inflammations, where the resolving phase is delayed or blocked. Very contradictory studies have been reported on the pro- and anti-inflammatory effects of humic substances (HSs) leading to significant disagreements between researchers. To a certain extent, this can be attributed to the chemical heterogeneity of this group of xenobiotics. Here we show for the first time that pro- and anti-inflammatory effects can occur by one HSs. We adapted an assay that uses green fluorescence-labeled zebrafish larvae and CuSO4 to indue an inflammation. In wild-type larvae, exposure to 50 µM CuSO4 for 2 h activated the production of reactive oxygen species, which can be monitored with a fluorescence dye (H2DCFDA) and a microplate reader. This allows not only the use of wild-type fish but also a temporal separation of copper exposure and inflammatory substance while retaining the high throughput. This modified assay was then used to evaluate the inflammatory properties of a fulvic acid (FA). We found, that the aromatic structure of the FA protects from inflammation at 5 and 50 mg C/L, while the persistent free radicals enhance the copper-induced inflammation at ≥ 300 mg C/L.Peer Reviewe

Towards sustainable water disinfection with peracetic acid in aquaculture: A review

eracetic acid (PAA) has a long history as an efficacious and eco-friendly disinfectant. It was first synthesised in 1902, and since then a wide range of applications has been developed in various industries. Aquaculture is a more recent industry wherein the potential of PAA is significant. As the global demand for sustainable development increases, there has likewise been growing interest in using PAA in aquaculture as an alternative to less environmentally friendly practices. PAA has no carcinogenic risk to humans (unlike formalin), has negligible harmful by-products (unlike chlorine-based disinfectants) and with appropriate precautions, the risks of causing severe human health damage is easier to control than ozone. Fish show strong physiological recovery and adaptation to PAA, whereas susceptible life stages of pathogens are highly vulnerable, enabling a safe and efficacious disinfection of the entire culture water and not the flow-restricted disinfection by such processes as ultraviolet radiation or ozone. The effective concentration of PAA against many fish pathogens is usually below 2 mg L−1, which is tolerable for most fish, and it has very low environmental risk due to rapid degradation. However, such degradation and the hydrodynamics in production-scale aquaculture systems complicate the practical use of PAA. In this review, we summarise key results of safe concentrations of PAA and its effectiveness specifically for fish farmers. We also outline major difficulties and possible solutions for practical uses of PAA. We intend to bring global attention to this compound and inspire future possibilities for its sustainable use as a water disinfectant in aquaculture.Towards sustainable water disinfection with peracetic acid in aquaculture: A reviewpublishedVersio

Phenol-rich fulvic acid as a water additive enhances growth, reduces stress, and stimulates the immune system of fish in aquaculture

Aquaculture has become imperative to cover the demands for dietary animal protein. Simultaneously, it has to overcome prejudices from excessive use of antibiotics and environmental impacts. Natural supplements are traditionally applied orally. In this study, we demonstrated another pathway: the gills. Humic substances are immunostimulants and a natural part of every aquatic ecosystem, making them ideal to be used as bath stimulants. Five and 50 mg C/L of a fulvic acid-rich humic substance was added for 28 days to the water of juvenile rainbow trout (Oncorhynchus mykiss). This fulvic acid is characterized by a high content of phenolic moieties with persistent free radicals and a high electron exchange capacity. The high concentration of the fulvic acid significantly increased growth and reduced the food conversion ratio and the response to a handling-stressor. Phagocytosis and potential killing activity of head kidney leukocytes were increased, as well as the total oxyradical scavenging capacity (TOSC) and lysozyme activity in the gills. In conclusion, immunostimulation via gills is possible with our fulvic acid, and the high phenolic content improved overall health and stress resistance of fish.Bundesministerium für Wirtschaft und Energie http://dx.doi.org/10.13039/501100006360Projekt DEALPeer Reviewe

Confirmation that pulse and continuous peracetic acid administration does not disrupt the acute stress response in rainbow trout

Peracetic acid (PAA) is considered an eco-friendly alternative to other antimicrobial agents of common use in aquaculture. The literature suggests that fish can habituate to PAA exposure based on a reduction of the fish corticosteroid response to PAA administration after repeated exposures. If that is true, PAA would also be a good option from the point of view of fish physiology. However, stronger evidence is needed to confirm that the use of PAA is welfare-friendly to fish. Besides habituation, other hypothetical factors such as desensitization, physiological exhaustion or PAA-mediated endocrine disruption could potentially explain the reduction in the corticosteroid response after repeated/prolonged PAA exposure. In this study, rainbow trout that had been exposed to PAA for several weeks were challenged with a secondary chasing stressor: fish were pursued with a dipnet for 1 min and their acute response was evaluated by measuring plasma cortisol, plasma glucose, plasma lactate and brain serotonergic activity. All fish were equally able to mount a normal physiological stress response to the secondary stressor independent of previous exposure to PAA. This suggests that the decrease in the cortisol response after repeated exposure to PAA, as seen in previous studies, is a true habituation to PAA administration, which supports the use of PAA as a welfare-friendly antimicrobial agent in aquacultur

Organic transformation of lignin into mussel-inspired glues: next-generation 2K adhesive for setting corals under saltwater

The 2-methoxyphenol units (G-units) in lignin are modified by demethylation and oxidation to provide the activated lignin as one part of an advanced biobased two-component (2K) adhesive system, which exhibits promising shear strengths in dry and underwater applications. The activation of lignin is straightforward and generates quinones via demethylation and periodate oxidation. These act as Michael acceptors and react smoothly with multi-thiol-star polymers to yield thiol-catechol connectivities (TCCs). The mussel-inspired material platform acts as a very robust and versatile adhesive, combining low-cost and readily available lignin with multi-thiols to achieve outstanding adhesion strengths of up to 15 MPa in dry application. In particular, the 2K system is compatible with the marine biological environment and shows no acute toxicity to sensitive organisms such as fish eggs. Thus, one possible application of this material could be an adhesive for setting temperature-resistant corals in damaged reefs.Peer Reviewe

The evolutionary legacy of size-selective harvesting extends from genes to populations

Size-selective harvesting is assumed to alter life histories of exploited fish populations, thereby negatively affecting population productivity, recovery, and yield. However, demonstrating that fisheries-induced phenotypic changes in the wild are at least partly genetically determined has proved notoriously difficult. Moreover, the population-level consequences of fisheries-induced evolution are still being controversially discussed. Using an experimental approach, we found that five generations of size-selective harvesting altered the life histories and behavior, but not the metabolic rate, of wild-origin zebrafish (Danio rerio). Fish adapted to high positively size selective fishing pressure invested more in reproduction, reached a smaller adult body size, and were less explorative and bold. Phenotypic changes seemed subtle but were accompanied by genetic changes in functional loci. Thus, our results provided unambiguous evidence for rapid, harvest-induced phenotypic and evolutionary change when harvesting is intensive and size selective. According to a life-history model, the observed life-history changes elevated population growth rate in harvested conditions, but slowed population recovery under a simulated moratorium. Hence, the evolutionary legacy of size-selective harvesting includes populations that are productive under exploited conditions, but selectively disadvantaged to cope with natural selection pressures that often favor large body size.Peer reviewe