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. 2025 Feb 2;16(1):16.
doi: 10.1186/s40104-024-01146-w.

Exploring single cell microbial protein as a sustainable fishmeal alternative in yellowtail kingfish (Seriola lalandi) diets: impacts on health and gut microbiome

Luke Pilmer  1   2 , Lindsey Woolley  3   4 , Alan Lymbery  3 , Chinh Dam  5   6 , Abigail Elizur  5 , Md Javed Foysal  7 , Gavin Partridge  3   4   8
Affiliations

Exploring single cell microbial protein as a sustainable fishmeal alternative in yellowtail kingfish (Seriola lalandi) diets: impacts on health and gut microbiome

Luke Pilmer et al. J Anim Sci Biotechnol. .

Abstract

Background: With the global expansion of aquaculture and the increasing demand for fish meal, identifying appropriate and sustainable alternative protein sources for aquafeeds has become essential. Single-cell protein (SCP), derived from methanotrophic bacteria, presents a promising alternative by converting methane into protein, potentially addressing both the need for alternative protein sources and reducing industrial greenhouse gas emissions. This study aimed to evaluate the effects of different levels of SCP inclusion (0%, 25%, 50%, and 75% fish meal replacement) on the health, gene expression, and gut microbiome of yellowtail kingfish (YTK, Seriola lalandi) following a 35-day growth trial.

Results: The study found that SCP inclusion at the highest level of fishmeal replacement (75%) induced a mild inflammatory response in the hindgut of the fish. However, micromorphological assessments of the hindgut, serum biochemistry, and gene expression analyses revealed no significant detrimental effects from SCP replacement. Notably, there were indications of improved lipid digestibility with SCP. Furthermore, SCP inclusion significantly enhanced microbial richness and altered the composition of the gut microbiome, introducing beneficial bacterial taxa that may contribute to improved gut health and resilience.

Conclusions: This study highlights SCP as a viable and sustainable alternative to fish meal in YTK diets. The findings suggest that SCP can be included in YTK diets without adverse health effects at moderate levels and may even offer benefits in terms of lipid digestibility and gut microbiome diversity. These results contribute to the advancement of more sustainable aquaculture practices.

Keywords: Alternative proteins; Gene expression; Methanotrophic bacteria; Microbiome; Yellowtail kingfish.

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Conflict of interest statement

Declarations. Ethics approval and consent to participate: All experiments were conducted under the Department of Primary Industries and Regional Development (DPIRD) Animal Ethics Committee approval (permit number: AEC 20-3-07). Consent for publication: Not applicable. Competing interests: The authors declare that they have no competing interests.

Figures

Fig. 1
Fig. 1
Myeloperoxidase activity in yellowtail kingfish hindgut after 35-day growth trial. Values are mean, with SE bars (n = 3). Different letters indicate significant differences between FM replacement levels, as determined by post hoc Tukey’s test
Fig. 2
Fig. 2
Alpha–beta diversity analysis of gut microbiota in yellowtail kingfish after 35-day growth trial. A and B Diversity of gut bacteria in terms of species richness and Shannon-Weiner index. Boxplots with different superscript letters at the top indicate significantly different mean values between additives (with and without) within a replacement level. C Number of shared and unique ASVs in fish-fed diets with and without additives (top), and at different SCP replacement levels (bottom). D and E PCoA plots representing beta-diversity for unweighted and weighted UniFrac distance metric
Fig. 3
Fig. 3
Relative abundance of bacteria at phylum (A) and genus (B) level in the gut of yellowtail kingfish after 35-day growth trial. Phyla and genera with more than 1% relative abundance were considered for plotting
Fig. 4
Fig. 4
Differential abundance (DA) of gut microbiota in yellowtail kingfish after 35-day growth trial. An LDA score of 2.0 and above following the Kruskal–Wallis, with a Bonferroni adjustment P-value of < 0.05, was considered for DA analysis
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