Submerged liquid fermentation of Ulva prolifera Muller tissue and applications for improving growth performance in juvenile abalone (Haliotis discus hannai Ino)

Ulva prolifera Muller, an alga rich in nutrients and bioactive compounds, is a natural feed resource for aquatic animals. In this study, instead of extracting polysaccharides (PUs) from U. prolifera, algae powder was used directly as the primary carbon source in a fermentation medium. Five percent (5%) algae powder was more conducive to fermentation. Using submerged liquid fermentation, the soluble components of U. prolifera were released efficiently in a 50-L fermenter. Levels of mannitol acquired using submerged liquid fermentation were 1.8 times higher than those acquired using the hot-water method, and polysaccharides were efficiently hydrolyzed to form oligosaccharides with an average molecular weight of approximately 3300 Da. Furthermore, a 2-month experiment was conducted to evaluate the effects of U. prolifera fermentation extracts on the growth performance of juvenile abalone (Haliotis discus hannai Ino). Diets containing algae fermentation extracts in concentrations ranging from 0.25 to 1% significantly increased linear shell growth rate (LGR), weight growth rate (WGR), and specific growth rate (SGR). Diets supplemented with fermentation extracts in concentrations of 0.5 and 1% significantly increased the degree of green coloration in the shell. Treatment of algae tissue using submerged liquid fermentation has the advantages of high efficiency and convenient process monitoring. Additionally, the technique can be scaled up for use in animal husbandry and aquaculture.