Microorganisms in Fish Feeds, Technological Innovations, and Key Strategies for Sustainable Aquaculture

Aquaculture, the world's fastest growing food sector, produces over half of all fish for human consumption. Aquaculture feeds include fishmeal and fish oil, extracted from wild-caught fish such as sardines, and poses ecological, food security, and economic drawbacks. Microalgae, yeasts, fungi, bacteria, and other alternative ingredients show promise as potential ingredients in aquafeeds that provide protein/amino acids, lipids, or omega-3 sources and sources of bioactive molecules. This review article discusses the issues that the literature often lacks data on, such as the recent development of using microorganisms, technological innovation, challenges, and opportunities to develop a low environmental footprint of aquaculture diet. The ingredients often require novel processing technology to improve digestibility and fish growth and reduce antinutritional factors. This is an important gap to fill because microalgae are the most frequently used organism in fish feed, particularly as a dietary supplement or mixed with other ingredients. The production, processing, and formulating steps can affect the nutritional qualities. Stepwise strategies are required to evaluate these ingredients for feed application, and in this article, I articulated the stepwise key approaches of evaluating nutritional and environmental response metrics to develop highly sustainable aquaculture feed using these microorganisms, which would guide a more judicious inclusion of these novel ingredients.

Production of rainbow trout (Oncorhynchus mykiss) using black soldier fly (Hermetia illucens) prepupae-based formulations with differentiated fatty acid profiles

The aquaculture sector is expanding rapidly and needs an increasing supply of fishery products. To ensure an ecological transition of this sector, alternative feed ingredients are required for fish nutrition. Potential alternatives include insects, particularly the black soldier fly (BSF, Hermetia illucens L. 1758), which is being increasingly targeted for their nutritional qualities and their sustainable production practices. BSF have a well-balanced amino acid profile; however, their fatty acid profile is not sufficiently balanced for most aquafeed formulations but can be modulated through their feed. In this study, two different batches of BSF prepupae (BSFP) were firstly produced: BSFP with a standard ω3 content (C18:3n-3 ≈ 1.36%) and ω3-enriched BSFP (C18:3n-3 ≈ 9.67%). Then, three isoproteic, -lipidic and -energetic trout feeds were formulated and produced: one control and two feeds containing 75% BSF meal as a substitute for fish meal (standard vs ω3-enriched-BSF). Finally, a trout feeding trial (n = 3 for each feed batch) in a recirculating aquaculture system was carried out for 75 days. BSFP meal inclusion in trout diets did not impact most nutritional and growth parameters of trout compared to the control; however, the coefficient of fatness increased, weight gain decreased and fatty acid profiles of fillets were altered. In conclusion, this study presents a more sustainable model of trout production by including insects from bioconversion of local byproducts in aquafeed.

Distribution, genetic diversity and potential spatiotemporal scale of alien gene flow in crop wild relatives of rice (Oryza spp.) in Colombia

BACKGROUND

Crop wild relatives (CWRs) of rice hold important traits that can contribute to enhancing the ability of cultivated rice (Oryza sativa and O. glaberrima) to produce higher yields, cope with the effects of climate change, and resist attacks of pests and diseases, among others. However, the genetic resources of these species remain dramatically understudied, putting at risk their future availability from in situ and ex situ sources. Here we assess the distribution of genetic diversity of the four rice CWRs known to occur in Colombia (O. glumaepatula, O. alta, O. grandiglumis, and O. latifolia). Furthermore, we estimated the degree of overlap between areas with suitable habitat for cultivated and wild rice, both under current and predicted future climate conditions to assess the potential spatiotemporal scale of potential gene flow from GM rice to its CWRs.

RESULTS

Our findings suggest that part of the observed genetic diversity and structure, at least of the most exhaustively sampled species, may be explained by their glacial and post-glacial range dynamics. Furthermore, in assessing the expected impact of climate change and the potential spatiotemporal scale of gene flow between populations of CWRs and GM rice we find significant overlap between present and future suitable areas for cultivated rice and its four CWRs. Climate change is expected to have relatively limited negative effects on the rice CWRs, with three species showing opportunities to expand their distribution ranges in the future.

CONCLUSIONS

Given (i) the sparse presence of CWR populations in protected areas (ii) the strong suitability overlap between cultivated rice and its four CWRs; and (iii) the complexity of managing and regulating areas to prevent alien gene flow, the first priority should be to establish representative ex situ collections for all CWR species, which currently do not exist. In the absence of studies under field conditions on the scale and extent of gene flow between cultivated rice and its Colombian CWRs, effective in situ conservation might best be achieved through tailor-made management plans and exclusion of GM rice cultivation in areas holding the most genetically diverse CWR populations. This may be combined with assisted migration of populations to suitable areas where rice is unlikely to be cultivated under current and future climate conditions.

Establishment of a sandwich enzyme-linked immunosorbent assay for specific detection of Bacillus thuringiensis (Bt) Cry1Ab toxin utilizing a monoclonal antibody produced with a novel hapten designed with molecular model

Cry1Ab toxin is commonly expressed in genetically modified crops in order to control chewing pests. At present, the detection method with enzyme-linked immunosorbent assay (ELISA) based on monoclonal antibody cannot specifically detect Cry1Ab toxin for Cry1Ab's amino acid sequence and spatial structure are highly similar to Cry1Ac toxin. In this study, based on molecular design, a novel hapten polypeptide was synthesized and conjugated to keyhole limpet hemocyanin (KLH). Then, through animal immunization with this antigen, a monoclonal antibody named 2C12, showing high affinity to Cry1Ab and having no cross reaction with Cry1Ac, was produced. The equilibrium dissociation constant (K _D) value of Cry1Ab toxin with MAb 2C12 was 1.947 × 10^-8 M. Based on this specific monoclonal antibody, a sandwich enzyme-linked immunosorbent assay (DAS-ELISA) was developed for the specific determination of Cry1Ab toxin and the LOD and LOQ values were determined as 0.47 ± 0.11 and 2.43 ± 0.19 ng mL^-1, respectively. The average recoveries of Cry1Ab from spiked rice leaf and rice flour samples ranged from 75 to 115%, with coefficient of variation (CV) less than 8.6% within the quantitation range (2.5-100 ng mL^-1), showing good accuracy for the quantitative detection of Cry1Ab toxin in agricultural samples. In conclusion, this study provides a new approach for the production of high specific antibody and the newly developed DAS-ELISA is a useful method for Cry1Ab monitoring in agriculture products. Graphical Abstract Establishment of a DAS-ELISA for the specific detecting of Bacillus thuringiensis (Bt) Cry1Ab toxin.

The impact of secondary pests on Bacillus thuringiensis (Bt) crops

The intensification of agriculture and the development of synthetic insecticides enabled worldwide grain production to more than double in the last third of the 20th century. However, the heavy dependence and, in some cases, overuse of insecticides has been responsible for negative environmental and ecological impacts across the globe, such as a reduction in biodiversity, insect resistance to insecticides, negative effects on nontarget species (e.g. natural enemies) and the development of secondary pests. The use of recombinant DNA technology to develop genetically engineered insect-resistant crops could mitigate many of the negative side effects of insecticides. One such genetic alteration enables crops to express toxic crystalline (Cry) proteins from the soil bacteria Bacillus thuringiensis (Bt). Despite the widespread adoption of Bt crops, there are still a range of unanswered questions concerning longer term agro-ecosystem interactions. For instance, insect species that are not susceptible to the expressed toxin can develop into secondary pests and cause significant damage to the crop. Here, we review the main causes surrounding secondary pest dynamics in Bt crops and the impact of such outbreaks. Regardless of the causes, if nonsusceptible secondary pest populations exceed economic thresholds, insecticide spraying could become the immediate solution at farmers' disposal, and the sustainable use of this genetic modification technology may be in jeopardy. Based on the literature, recommendations for future research are outlined that will help to improve the knowledge of the possible long-term ecological trophic interactions of employing this technology.

Zapatista corn: a case study in biocultural innovation

In November 2001, Nature published a letter in which University of California Berkeley's biologists claimed to have found evidence of genetically modified (GM) DNA in regional varieties of maize in Oaxaca, even though the Mexican government had banned transgenic corn agriculture in 1998. While urban protesters marched against the genetic 'contamination' of Mexican corn by US-based agricultural biotech firms, rural indigenous communities needed a framework for understanding concepts such as GM before they could take action. This article analyzes how the indigenous organization, the Zapatistas, mobilized a program to address this novel entity. Their anti-GM project entailed educating local farmers about genetics, importing genetic testing kits, seed-banking landrace corn and sending seeds to 'solidarity growers' around the world. This article explores material-semiotic translations to explain one of the central aspects of this project, the definition and circulation of Zapatista corn--an entity defined not only through cultural geography, but also technological means. Through its circulation, Zapatista corn serves to perform a biocultural engagement with Zapatista's political project of resistance to neoliberalism. While much has been written about both regulatory policy and consumer activism against GM in the Global North, Zapatista corn also provides a case study in indigenous, anti-GM activism founded on biocultural innovation and the creation of alternative networks for circulating corn.

Labeling of genetically modified food: closer to reality in the United States?

Within the broader context of several related biotech developments, including the proliferation of GM food in American grocery stories, the recent decision by Whole Foods Market, Inc. to require the labeling of all genetically modified (GM) organism products sold in its stores by 2018, and the development of GM animals for consumption, this essay asks whether the United States is inching towards a policy of mandatory GM food labeling. The analysis highlights aspects of the biotechnology policy debate in the United States and European Union, and traces public opinion as well as grassroots and legislative efforts aimed at GM food labeling. Findings show that activities at the federal level do not suggest any major regulatory changes regarding labeling in the near future; however, a growing number of individual states are considering GM food labeling legislation and political momentum in favor of labeling has picked up in recent years. Voluntary labeling by food companies may also become increasingly common.

Isolation and functional characterisation of banana phytoene synthase genes as potential cisgenes

Carotenoids occur in all photosynthetic organisms where they protect photosystems from auto-oxidation, participate in photosynthetic energy transfer and are secondary metabolites. Of the more than 600 known plant carotenoids, few can be converted into vitamin A by humans and so these pro-vitamin A carotenoids (pVAC) are important in human nutrition. Phytoene synthase (PSY) is a key enzyme in the biosynthetic pathway of pVACs and plays a central role in regulating pVAC accumulation in the edible portion of crop plants. Banana is a major commercial crop and serves as a staple crop for more than 30 million people. There is natural variation in fruit pVAC content across different banana cultivars, but this is not well understood. Therefore, we isolated PSY genes from banana cultivars with relatively high (cv. Asupina) and low (cv. Cavendish) pVAC content. We provide evidence that PSY in banana is encoded by two paralogs (PSY1 and PSY2), each with a similar gene structure to homologous genes in other monocots. Further, we demonstrate that PSY2 is more highly expressed in fruit pulp compared to leaf. Functional analysis of PSY1 and PSY2 in rice callus and E. coli demonstrates that both genes encode functional enzymes, and that Asupina PSYs have approximately twice the enzymatic activity of the corresponding Cavendish PSYs. These results suggest that differences in PSY enzyme activity contribute significantly to the differences in Asupina and Cavendish fruit pVAC content. Importantly, Asupina PSY genes could potentially be used to generate new cisgenic or intragenic banana cultivars with enhanced pVAC content.

Position of the American Dietetic Association: Food and Nutrition Professionals Can Implement Practices to Conserve Natural Resources and Support Ecological Sustainability

It is the position of the American Dietetic Association to encourage environmentally responsible practices that conserve natural resources, minimize the quantity of waste generated, and support the ecological sustainability of the food system-the process of food production, transformation, distribution, access, and consumption. Registered dietitians and dietetic technicians, registered, play various roles in the food system and work in settings where efforts to conserve can have significant effects. Natural resources that provide the foundation for the food system include biodiversity, soil, land, energy, water, and air. A food system that degrades or depletes its resource base is not sustainable. Making wise food purchases and food management decisions entails understanding the external costs of food production and foodservice and how these external costs affect food system sustainability. This position paper provides information, specific action-oriented strategies, and resources to guide registered dietitians and dietetic technicians, registered, in food decision making and professional practice. Food and nutrition professionals also can participate in policy making at the local, state, and national levels, and can support policies that encourage the development of local sustainable food systems. Our actions today have global consequences. Conserving and protecting resources will contribute to the sustainability of the global food system now and in the future.

Impact environnemental des cultures transgéniques

La publication d’un article scientifique sur les effets néfastes d’un hybride de maïs transgénique exprimant une δ-endotoxine duBacillus thuringiensiscontre des larves du papillon monarque causait, il y a quelques années, une controverse sans précédent sur l’impact environnemental des caractères recombinants introduits au bagage génétique des cultures agricoles. Le présent article de synthèse, complémentaire à un article de ce même numéro abordant la migration des transgènes dans l’environnement (Michaud 2005), discute de l’impact des caractères recombinants encodés par les transgènes sur l’incidence et le développement des différents organismes vivants du milieu. L’impact des nouveaux caractères est d’abord considéré à l’échelle des écosystèmes, à la lumière des effets exercés par les pratiques agricoles courantes sur la diversité biologique au champ. L’impact de ces caractères est ensuite considéré en fonction des interactions spécifiques établies au champ ou en conditions de laboratoire entre la plante modifiée et une gamme d’espèces modèles incluant des ravageurs herbivores secondaires, des arthropodes prédateurs et différents organismes du sol.