ISSUE FOCUS 74 FEED & ADDITIVE MAGAZINE August 2025 Alternatives to Fishmeal: SINGLE-CELL PROTEINS FOR THE FUTURE OF AQUACULTURE Dr. Federico Melenchón Ramírez Product Manager – Functional Health Ingredients Unibio A/S Alternatives to fishmeal are becoming increasingly important as the aquaculture industry faces rising long-term prices and supply constraints. To adapt, the industry should diversify its raw materials with alternative proteins that deliver equivalent nutritional value. Among these alternatives, single-cell proteins stand out as strong candidates that could partially or entirely replace fishmeal and reduce supply uncertainties. Anyone familiar with aquaculture nutrition knows there has been a longstanding global concern about the sustainability of fishmeal as an ingredient, both in environmental and economic terms. Those who have been in the field for the past 20-30 years know that this concern has been partially addressed by plant-based ingredients, an approach that is attractive in terms of cost but not ideal for fish gut health.1 If we narrow the timeframe further, anyone who has been in the sector over the past 15 years will know that there is now a growing number of promising alternatives aimed at reducing the pressure on the planet’s resources, ranging from animal-sourced ingredients (such as poultry by-products and insect meals) to microalgae and fermented proteins derived from single-cell biomass.2 A quick search on fermentation technologies and other single-cell culture methods for biomass production suggests that several hundred microorganism strains have been cultured for food or feed in recent years. If we limit it to cases with commercial potential, the number of strains studied ranges between 150 and 300. If we further narrow it to those included in significant amounts in aquaculture feed, the count falls to between 15 and 30 strains, which is still a very significant number.3 TYPES OF BIOMASSES Yeast Among the numerous microorganisms studied, yeast is one of the most extensively researched and widely commercialized sources of single-cell protein, with many competitive products currently available in food and feed supply chains. These products often show high protein content, but beyond protein, one of the most interesting features of yeast is the presence of cell wall components such as beta-glucans. Beta-glucans are known enhancers of the innate immune response and can interact with immune receptors to promote a defensive reaction. This immunostimulatory effect is particularly valuable in aquaculture since fish are not naturally exposed to high levels of beta-glucans, which makes these compounds effective functional ingredients.4,5
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