Putting these numbers into practice will require understanding how management practices affect both bird and CBB densities.The availability of safe, high-quality food for the burgeoning world population continues to be a major challenge in light of the deterioration of natural resources coupled with climate change. To feed the estimated 10 billion people safely and sustainably by 2050, the world will need to produce significantly more food. It is anticipated that global demand for meat will increase by 70% from today, and planetary resources will be insufficient to meet the demand of the world population by 2050. Within this larger global challenge, aquatic sources provide nutritional protein-rich foods, including omega- 3-enriched sources of fatty acids and bio-available micro-nutrients. Stagnant levels of fish harvested from open water fisheries and the growing challenges with the sustainability of aquaculture systems are concerns. To adequately feed the growing global population by 2050, increases in seafood production of 100% are projected as a need. Decade-wise comparisons of global per capita consumption, capture fisheries production and aquaculture production from 2000 to 2020 based on FAO data are given in Fig. 1. Hence, plastic growing bag there is an imperative to establish alternative sources of fish and shellfish to effectively meet the growing global protein demand in the foreseeable future.
Presently, 89% of the aquatic animals produced—equal to 157.4 million tons—are used for human consumption, considering the per capita consumption of 20.2 kg fish per year by 7.8 billion people. The rest is used mainly for non-food uses including fish oil and fish meal production. Future projections for capture fisheries and aquaculture production by 2050 are 98.3 and 140 million tons, respectively. Thus, increases in future fish production will rely mostly on aquaculture production, which is challenging in the context of sustainable production. For fish production to be maintained at a sustainable level, critical efforts will be required to provide larger volumes of feed to support aquaculture, to maintain quality for aquatic environments, to reduce pressure on wild aquatic organisms used for food and provide quality aquatic foods to consumers. These challenges prompt the development of alternative sources of aquatic food through cell cultivated approaches.Cell-cultivated seafood has gained attention as an alternative sustainable food production system, where animal cells are grown in vitro using cell culture techniques to form edible seafood products without the need for the animal. Cellular agriculture is one of the key transformative food production systems to help address the above challenges, which originated with the cultivation of goldfish in a study funded by NASA. Cell-cultivated fish production requires the large-scale cultivation of cells to generate large masses of seafood-relevant cells and tissues. These cells and tissues can be used to form unstructured products such as surimi or fish fingers using well-established food processing techniques, or they can be further cultured on three-dimensional biomaterial scaffolds to generate structured products akin to fish fillets.
The many advantages to producing seafood from cell cultures rather than using native fish includes improved freshness, food quality and avoiding nonedible components such as bones, skin, shells, and scales as wastes that can negatively impact the environment. Cell-cultivated seafood may also shorten food production cycle time and provide continuous production; cell cultures may require weeks to generate functional foods and may do so in a continuous manner . Fisheries and aquaculture are relatively sustainable food production systems compared to terrestrial livestock, however, due to overfishing, pressure on wild stocks, emerging diseases, antibiotic-resistant bacteria, global warming, and marine acidification with adverse impact on organisms’ physiology, loss of biodiversity and species migration, byproducts of production, microplastics, chemical contaminants in waters, and the lack of clean water , the seafood industry requires alternative and innovative production systems to overcome these current challenges.There are several gaps in research and development to be filled in order to progress cell-cultivated seafoods. Limited seafood cell lines: Producing seafood from fish cell cultures is an intriguing opportunity for cellular agriculture, yet few fish cell lines are currently available that have direct relevance to seafood production. Cell-cultivated seafood processes rely on native seafood sources for harvesting muscle and fat cells, which are then immortalized. Both cell isolation and the immortalization processes remain challenging.
For example, access to embryonic stages of many aquatic organisms as a source of stem cells is difficult. The number of cell sources has been expanding thanks to continuous research. Many of these sources, however, still need to be validated in a large-scale culture. Limited knowledge of seafood cell differentiation: There remains limited knowledge in terms of in vitro fish, crustacean, and mollusk muscle cell or fat cell proliferation, differentiation, and maturation. Omics-based methods, including genomics, proteomics, and metabolomics, are helping to elucidate factors involved in the different stages of differentiation to accelerate cell-cultivated seafood production. Further, a number of studies with fish have provided insights into growth factor requirements and growth conditions . Myogenic precursors from juvenile trout showed higher proliferation and differentiation rates than adult trout myogenic precursors, and insulin-like Growth Factor and IGF-2 stimulated the proliferation in primary cell cultures of myoblasts from rainbow trout . Gilthead sea bream myocytes were cultured to evaluate the role of IGFs in muscle growth and differentiation via the regulation of myogenic regulatory factors expression. At the beginning of the cell culture and during the proliferation, the IGF-2 expression was highest. Additionally, further evaluations indicated that myod2 and myf5 expression was increased by IGF-2, whereas IGF-1 increased mrf4 and myogenin expression. Lack of serum-free media: Serum-free media has been developed for mammalian cells, yet this remains a challenge for cell-cultivated seafood. Cell line development for seafood can require up to 20% serum, making cell based seafood production unsustainable and expensive. Reducing serum can result in changes in morphology or slower to no cell growth. Reduction of serum in fish cell cultures has been achieved using IGF-2, algal extracts, and protein hydrolysates, but elimination of serum without negative impact on growth remains a challenge . More research is required to develop serum alternatives for cellular aquaculture, such as specific plants or bacterial/algal-based products. Limited genetic tools: Exploring genetic modifications for seafood cells, wholesale grow bags to accelerate both understanding of cell proliferation and differentiation, as well as to develop cell lines, remains challenging due to the few genetic tools developed for seafood cells. Yet, optimization of immortalization and trans-differentiation processes through genetic modification, including CRISPR-Cas9 editing of fibroblasts that convert them into skeletal muscle or adipose cells, will address some of the cell sourcing challenges for cell-cultivated seafood. Induced pluripotent stem cells are available for adult zebrafish, with limits to other publicly available other seafood species. There remains limited knowledge of differentiation pathways in aquatic species other than zebrafish. Genetic tools in other, traditionally consumed, species need to be pursued. Given that these technologies still require genetic modification, consumer acceptance and reactions to the consumption of genetically modified cells must be evaluated. Scale Up Demonstration: Compared to mammalian cells, fish cells may be more suitable for bioreactor production due to their tolerance for hypoxic conditions, which reduces the need for active oxygenation; their increased tolerance for different pHs; and in some cases, their growth at lower temperature to reduce energy costs. However, long doubling times are problematic and scale up data remains to be demonstrated. Lack of available consumer-ready products: The inclusion of heme proteins in plant-based meat increased meat-like flavor and natural color. Similar approaches are needed for aquatic cell-cultured foods to address consumer perceptions.
The Peptide Atlas and Protein Map developed from Rohu is a useful source for identifying proteins involved in the quality and color of cell-cultivated seafood. Nutrition, flavor, texture, and quality of products and cultural relevance are important parameters that will need to be addressed for cell-cultivated seafood to achieve consumer acceptance as the field progresses. Flavor in conventional seafood is mainly due to the fatty acids, and some amino acids. Developing these flavors in the cultivated meat could be achieved by cell engineering to generate specific amino acids and fatty acids, manipulating cell culture media to contain more marine flavor-based compounds such as protein hydrolysates from marine plants, and adding flavor extracts to the final products.Developing cell-cultivated seafood starts by isolating embryonic stem cells, adult stem cells, or generating induced pluripotent cells from the species of interest . Despite efforts to establish cell lines from aquatic organisms , the challenge remains to isolate and immortalize viable cells . Tissue selection is the first step for sampling, in the case of fish samples for myogenic cells, this often involves using white muscles with significantly less fat content compared to red muscles, however, the spatial arrangement differs among species . In order to isolate cells, adult tissue selection for mollusks plays a crucial role in establishing primary cell culture methods. Mollusks, such as oysters, have diverse tissue types that can dictate the culture conditions and cell dissociation methods. Tissue from three main oyster species, Pacific , Eastern , and European Flat oyster , have been studied for drug, toxicity, and disease research, including embryo, heart, mantle, digestive gland, gill, ventricle, and adductor tissues . Among oyster tissues studied, heart tissue was most frequently selected as it had better potential in establishing a permanent cell line than oyster embryos. These previous studies indicate that the tissue of origin often dictates the success of oyster cell culture, along with culture conditions and decontamination treatments. A significant challenge for seafood cell isolation is contamination from other species, particularly for marine filter feeder bivalves such as oyster, mussel, clam and scallop. Protozoans , amoeba, motile zoospores, sporangia, yeast, endospores, and microalgae are common contaminants in marine invertebrate cell culture. Finding optimal antibiotics and anti-fungal conditions during the initial cell isolation step is also challenging because high concentrations candamage or kill the desired cells, and low concentrations may not effectively eliminate the contaminating microbes. In order to develop cells suitable for bioprocesses for seafoods, immortalized cells are required. Three methods of immortalization are generally pursued, spontaneous genetic processes, genetic modification approaches such as the expression of the catalytic subunit of telomerase , or genetic inactivation of p53/p14/Rb . Spontaneous immortalization has benefits and limitations. For example, spontaneously immortalized cells are not considered genetically modified , which allows companies access to European markets that restrict the use of GM foods. However, this immortalization process is not controlled, thus additional genetic changes are feasible. In addition, every cell type has its own susceptibility towards spontaneous immortalization. For example, fish cell lines have a higher susceptibility for spontaneous immortalization due to the high regenerative capacity of the adult stem cell population compared to mammals with more effective DNA repair mechanisms. For cell-cultivated seafood production, spontaneous immortalized cell lines from Atlantic mackerel were developed and a skeletal muscle cell line was confirmed through characterization of muscle stemness and differentiation via paired-box protein 7 and myosin heavy chain immunostaining, respectively. Importantly, an adipocyte-like phenotype was demonstrated for these cells through lipid accumulation from the environment, confirmed via Oil Red O staining and quantification of neutral lipids, as an alternative path to adipogenesis utilizing adipose-derived cells. Limited antibody markers for fish derived cells, including adipocytes and myocytes, continue to make cell identification a challenge for the field.A simple basal medium with added artificial seawater or sterile seawater helped to provide osmolarity similar to marine habitats. For example, for oyster cell culture media, osmolarity was adjusted to 650–720 mmol/kg31. The most common medium used for many aquatic organisms in cell culture is L-15, which contains salts, amino acids, galactose, vitamins, and minerals. However, the L-15 medium contains no proline or taurine, which are present at high levels in the body fluids or tissues of aquatic organisms. Proline and taurine are likely essential components for cell proliferation in mammalian cells. Therefore, adding proline or taurine to oyster cell culture media by using oyster body fluid or tissue extracts could be necessary for supporting cell proliferation. In addition to basal media, many media supplements and growth factors such as fetal bovine serum , adult organism soft body fluid, embryo or gonad extract, fibroblast growth factor , insulin, and epidermal growth factor have been tested for cell proliferation but with inconsistent outcomes. Different cell culture media, supplements, and incubation temperatures used for bivalve cell culture are presented in Table 2. For oyster cell cultures, penicillin, streptomycin, and amphotericin B are the most commonly used antibiotics.