ISSUE FOCUS FEED & ADDITIVE MAGAZINE August 2025 75 Microalgae Microalgae are gaining recognition as a promising and scientifically validated protein source for aquaculture. These tiny organisms offer impressive nutritional value. For example, Chlorella vulgaris and Spirulina platensis can contain up to 70% protein by dry weight and provide an amino acid profile that fulfills the needs of several fish species. Their wide biological diversity allows producers to develop tailored feed formulations that address the dietary needs of specific aquaculture species. One notable genus of green microalgae, Nannochloropsis, is naturally high in eicosapentaenoic acid (EPA), a long-chain omega-3 polyunsaturated fatty acid essential to fish health and development.6 In addition to their nutritional benefits, many microalgae species can grow in saline or wastewater environments. This makes them a practical choice for integrated production systems that aim to reduce environmental impact.7 As research progresses, advances in strain selection and metabolic engineering will further refine the use of microalgae to meet species-specific nutritional needs. Considering all of the above, microalgae is a strong candidate for the next generation of sustainable protein sources for aquafeed. Microbial (bacterial) Another type of biomass with a promising outlook is microbial biomass. As some of the simplest organisms on the phylogenetic scale, bacteria can devote more energy to pure growth and achieve some of the highest biomass production ratios known in nature. This relative simplicity, combined with millions of years of evolution, has enabled the development of numerous production methods, allowing bacteria to thrive and adapt to diverse ecological and industrial environments. These cultivation advances have also facilitated the development of bacteria-based production systems using diverse carbon feedstocks. Sugar-based bacteria, such as Corynebacterium glutamicum, convert carbohydrates into protein-rich biomass, allowing agricultural by-products or waste sugars to be used as feedstock. Methanol-based bacteria, such as Methylobacterium species, utilize methanol, a simple one-carbon molecule often derived from industrial processes. Similarly, methanotroph bacteria consume methane, a potent greenhouse gas, and convert it into nutritionally valuable biomass that has shown good results for aquaculture feeds. These methanotroph bacteria naturally thrive at the bottom of lakes, where they play a key role in methane consumption as part of their life cycle and serve as an important protein source for fish and other aquatic organisms. Today, this natural process is being replicated at industrial scale to produce protein biomass.8,9 A recent study by Ruiz et al. (2023) showed that Uniprotein®, a protein-rich biomass produced by methane-fed microbes, can replace up to 100% of fishmeal in a rainbow trout feed formulation (15% total feed inclusion). No statistical differences were found in growth performance. A quadratic regression analysis further indicated that replacing approximately 42% of the fishmeal would be optimal for this formulation in rainbow trout, corresponding to about 6% Uniprotein® inclusion in the feed.10 In commercial settings, however, nutritionists at large feed companies are implementing 8% inclusion as a practical sweet spot (Figure 1). 210 205 200 195 190 185 180 175 0 20 40 60 80 100 Final Body Weight (g) Fishmeal Replacement 41.7% Figure 1. Optimal replacement of fishmeal with Uniprotein® in rainbow trout feed (Ruiz et al.,2023)
RkJQdWJsaXNoZXIy MTUxNjkxNQ==