Toward Sustainability: An Overview of the Use of Green Hydrogen in the Agriculture and Livestock Sector.

The agro-livestock sector produces about one third of global greenhouse gas (GHG) emissions. Since more energy is needed to meet the growing demand for food and the industrial revolution in agriculture, renewable energy sources could improve access to energy resources and energy security, reduce dependence on fossil fuels, and reduce GHG emissions. Hydrogen production is a promising energy technology, but its deployment in the global energy system is lagging. Here, we analyzed the theoretical and practical application of green hydrogen generated by electrolysis of water, powered by renewable energy sources, in the agro-livestock sector. Green hydrogen is at an early stage of development in most applications, and barriers to its large-scale deployment remain. Appropriate policies and financial incentives could make it a profitable technology for the future.

Cultivable microalgae diversity from a freshwater aquaculture filtering system and its potential for polishing aquaculture-derived water streams.

AIMS: Microalgae are ubiquitous in aquatic environments, including aquaculture farms, but few studies have delved into their phytoplankton diversity and bioremediation potential. In this study, the cultivable phytoplankton of a rainbow trout freshwater aquaculture farm was isolated, phylogenetically analysed and used to assemble a consortium to polish an aquaculture-derived effluent, with low concentrations of ammonium, nitrite and nitrate. METHODS AND RESULTS: Through standard plating in different selective media, a total of 15 microalgae strains were isolated from sludge from a rotary drum filtering system which removes suspended solids from the water exiting the facility. Based on 18S rRNA gene sequences, isolates were assigned to nine different genera of the Chlorophyta phylum: Asterarcys, Chlorella, Chloroccocum, Chlorosarcinopsis, Coelastrella, Desmodesmus, Micractinium, Parachlorella and Scenedesmus. Species from most of these genera are known to inhabit freshwater systems in Galicia and continental Spain, but the Coelastrella, Asterarcys or Parachlorella genera are not usually present in freshwater streams. In an onsite integrative approach, the capacity of a consortium of native microalgae isolates to grow on aquaculture-derived effluents and its nutrient removal capacity were assessed using a raceway pond. After 7 days, removal efficiencies of approximately 99%, 92% and 49% for ammonium, nitrite and nitrate, respectively, were achieved concomitantly with a microalgae biomass increase of ca. 17%. CONCLUSIONS: Sludge from the aquaculture filtering system presents a high diversity of microalgae species from the Chlorophyta phylum, whose application in a consortial approach revealed to be efficient to polish aquaculture-derived effluents with low nutrient content. SIGNIFICANCE AND IMPACT OF THE STUDY: The use of native microalgae consortia from aquaculture systems can contribute to the development of efficient treatment systems for low-nutrient wastewater, avoiding nutrients release to the environment and promoting water recirculation. This may further strengthen the use of phycoremediation at the industrial scale, as an environment-friendly strategy.

Bioremediation with freshwater bivalves: A sustainable approach to reducing the environmental impact of inland trout farms.

Integrated multi trophic aquaculture (IMTA) is well developed in seawater, while the only suitable organisms for bioremediation in freshwater are bivalves. The aim of this research has been to investigate a novel system, based on freshwater bivalves integrated with rainbow trout, for the bioremediation of inland aquaculture systems. The Unionid species selected for the experiments was Sinanodonta woodiana. Five mesocosm experiments were conducted to evaluate the efficiency of mussels in filtering the total bacteria and Aeromonas hydrophila, as well as their clearance efficiency on trout farm wastewater. The temperatures, dissolved oxygen, nitrates, and phosphates were monitored and were all within the physiological tolerance range of the species in all the experiments. The feasibility of bioremediation with S. woodiana in trout farming has thus been demonstrated, and among the tested rearing densities (3.75; 7.5; 15; 30 and 60 kg m-3) that of 7.5 kg m-3 was found to be optimal. The net reduction of the total bacterial concentration was as much as 72%, while that of A. hydrophila reached a level of 95-98%. No relevant effects of the mussels on particulate suspended material or sedimented material was observed, regardless of the temperature. The efficiency of freshwater bivalves in reducing the bacterial load, in particular toward A. hydrophila, indicates a bioremediation system with the possibility of interesting applications on inland fish farms, and as a biotechnological tool against the diffusion of antibiotic resistance in aquaculture.

Prevalence and antibiotic sensitivity of bacteria isolated from imported ornamental fish in Italy: A translocation of resistant strains?

The rapid expansion of the ornamental aquaculture industry over the past decades has resulted in a concomitant increase in the use of antibiotics to combat infectious diseases. The aim of this study was to assess the possible role of ornamental fish in the translocation of antibiotic resistant bacteria, with possible consequences for aquarium and public health. We assessed the prevalence of bacterial infections and the antibiotic resistance profile of bacteria isolated from 134 ornamental fish imported into northwest Italy during two years of monitoring. Ornamental fish analyzed were imported mainly from Singapore (40%) and Israel (20%), followed by Thailand (13%), Sri Lanka (12%), Czech Republic (7%), Vietnam (5%) and Indonesia (3%). The most commonly imported fish were freshwater species, particularly those belonging to the Poeciliidae family. Bacteriological exam was positive in 68% of the fish examined. The most frequently isolated bacterium was Aeromonas sobria (37%). Bacteria showed resistance against lincomycin, ampicillin, oxytetracycline and tetracycline. Sensitivity was found for florfenicol, chloramphenicol, gentamicin, and trimethoprim/sulfamethoxazole. Odds ratio (OR) values were calculated as a measure of the association between antibiotic resistance of A. sobria and selected factors (country of origin, fish family and fish species), considering Thailand, Poeciliidae and Poecilia reticulata as control cases. Higher values were found for Vietnam (OR 5.6) and Xiphophorus helleri and X. maculatus (OR 3.0 and 3.7 respectively). Our findings underline the need to improve targeted surveillance of antimicrobial resistance and prevent the translocation of resistant or multi-resistant bacterial strains in ornamental fish, especially in fish imported from countries where surveillance is limited or lacking.

Integrated Multitrophic Aquaculture By-Products with Added Value: The Polychaete Sabella spallanzanii and the Seaweed Chaetomorpha linum as Potential Dietary Ingredients.

Aquaculture expansion is limited by the negative environmental impact of the waste and the need for alternative sources in the diet of reared fish. In this framework, for the first time, the survival rates, biomass gain, and fatty acid profiles of the polychaete Sabella spallanzanii and the macroalga Chaetomorpha linum, reared/cultivated as bioremediators in an integrated multitrophic aquaculture system (IMTA), were evaluated for their potential reuse applications. Results showed that these organisms represent a natural source of omega-3 and omega-6. On account of the overall results and the high biomass obtained as by-products, a preliminary study was performed employing both S. spallanzanii and C. linum as new dietary ingredients to feed different sized Dicentrarchus labrax. Fish survival rate, biomass growth, and specific growth rate were determined resulting in no significant differences between control and treated fishes. Histological analyses showed no alterations of the stomach tunica mucosa and submucosa in treated fishes. The eco-friendly approaches applied in the here-realized IMTA system could guarantee the achievement of sustainable by-products represented by the bioremediators S. spallanzanii and C. linum, as well as their reliability as a natural source of compounds beneficial to fish and human health.

Investigation of the protein profile of silkworm (Bombyx mori) pupae reared on a well-calibrated artificial diet compared to mulberry leaf diet.

BACKGROUND: Silkworm pupae is the main by-product of the sericulture industry with an interesting nutritional profile, especially in terms of proteins. In consideration of its possible use as a food or food ingredient in Western countries, a comparative proteomic experiment has been performed to investigate the differences of the protein profile of male and female silkworm pupae reared on mulberry leaves or on an artificial diet. METHODS: The nutritional profile of lyophilized silkworm pupae in terms of dry matter and ash was evaluated according to the AOAC procedures, the total nitrogen content was determined by a nitrogen analyzer and the silkworm pupae gross energy value was measured using an adiabatic calorimetric bomb. The comparative proteomic analysis was performed on male and female silkworm pupae reared on mulberry leaves or on the artificial diet. Proteins were separated by two-dimensional electrophoresis and, after a multivariate statistical analysis, the differentially expressed proteins were identified by LC-MS/MS. RESULTS: The comparative proteomic approach highlighted 47 silkworm pupae proteins differentially expressed comparing diet and gender. PCA analysis showed that seven proteins were more effective in discriminating the sex and five were more effective in discriminating the diet type. In spite of the above-mentioned differences in the silkworm pupae protein profile, no strong alteration of the pupa physiological traits have been demonstrated, suggesting a general silkworm pupae flexibility to adapt to a well-balanced artificial diet. Differences in lipid transport and metabolism were found among the experimental groups, that might have a relevant effect on the timing and on hormone secretion. This aspect may also affect silk production, as univoltine strains are the most productive. The proteomic data provided in this work, may offer a contribution in understanding also the influence of gender and farming strategy on the allergen profile of Bombyx mori, when used as food or as a food ingredient. Female silkworm pupae reared on mulberry leaves seemed to contain lower levels of known allergens than those reared in the other experimental conditions; these findings will have to be taken into account when farming B. mori for food production purposes. However, our results need to be supported by further characterization of the allergenic potential of B. mori.