Aquaculture relies heavily on formulated feed, with feed costs accounting for approximately 50% of the total production expenses. High-protein feed is expensive, and some raw materials are dependent on imports. Organic waste, primarily from food scraps and agricultural residues, can be considered feed ingredients to reduce costs. Through fermentation, the nutritional value of these feeds can be enhanced, promoting the growth of aquatic animals, such as fish, and reducing overall costs. Enzymatic hydrolysis and microbial fermentation are commonly used bioprocessing methods, particularly suitable for unconventional feed sources. These methods not only enhance the nutritional value of the feed but also reduce the content of anti-nutritional factors, improving feed digestibility. Enzymatic hydrolysis is often combined with microbial fermentation to produce more efficient novel biofeeds. This synergistic approach enhances microbial fermentation efficiency and the degradation of macromolecules, further improving the nutritional value of the feed, promoting intestinal digestion and absorption, and enhancing animal production performance. Compared to treatments with single strains or enzymes, the synergistic fermentation of feed with microorganisms and enzymes shows more significant effects. This review summarizes the fermentation mechanisms and classifications of enzymatic hydrolysis and microbial fermentation in producing novel biofeeds. It also outlines the advantages of this synergistic process and its progress in aquatic animal production, providing a scientific basis for its broader application in aquaculture.

In this study, the effects of talc microparticles on mycelia morphology and ε-poly-L-lysine (ε-PL) production by Streptomyces sp. M-Z18 were investigated for the first time. Changing mycelia morphology with talc microparticles has resulted in ε-PL production being enhanced. Talc microparticles caused a decrease of pellet diameter from 297.63 ± 156.33 to 205.65 ± 71.56 μm in shake-flask fermentation. Moreover, the maximum ε-PL production reached 2.51 ± 0.08 g L⁻¹ in the presence of 10 g L⁻¹ talc microparticles, which was increased by 50.30%, compared to the control (1.67 ± 0.11 g L⁻¹). The scale-up processes were performed in batch and fed-batch fermentations in a 5 L fermenter with 10 g L⁻¹ talc addition, and the final ε-PL production of 30.57 g L⁻¹ was obtained at 168 h, with 44.06% increase over the control. Talc microparticles of 10 g L⁻¹ were then supplied to the fed-batch fermentation with acidic pH shock and agro-industrial by-products, and ε-PL production was further increased to 62.36 g L⁻¹ at 192 h, compared to 54.70 g L⁻¹ of the control without supplementary talc. This is also the highest ε-PL production reported so far in the literature. These results suggested that talc addition could be an efficient and universal approach for enhancing ε-PL production in industry.