Alternative proteins in Aquafeeds: Evaluating methanotrophic and hydrogenotrophic bacterial meals in yellowtail kingfish diets

Authors

Luke Pilmer, Department of Primary Industries and Regional Development, Western AustraliaFollow
Gavin Partridge, Department of Primary Industries and Regional Development, Western Australia
Chelsea Woods, Department of Primary Industries and Regional Development, Western AustraliaFollow
Md Javed Foysal, The University of Newcastle
Md Reaz Chaklader, Department of Primary Industries and Regional Development, Western AustraliaFollow
Alan J. Lymbery, Murdoch University
Lindsey Woolley, Department of Primary Industries and Regional Development, Western AustraliaFollow

Document Type

Article

Publication Date

11-7-2025

Journal Title

Aquaculture

ISSN

ISSN: 0044-8486, eISSN: 1873-5622

Keywords

Single-cell protein, Methanotrophic bacteria, Hydrogenotrophic bacteria, Alternative protein, Seriola lalandi

Disciplines

Aquaculture and Fisheries

Abstract

This study evaluated the effects of replacing fishmeal with microbial single-cell proteins (SCPs) in diets for juvenile yellowtail kingfish (YTK, Seriola lalandi), assessing growth, feed efficiency, nutrient digestibility, gut histology and microbiome, blood biochemistry and gene expression. Eight experimental diets were formulated, using methanotrophic (SB) and hydrogenotrophic (LT) SCPs at inclusion levels of 4 %, 8 %, and 16 %, alongside a control diet (42.2 % fish meal) and a combination diet (4 % SB + 4 % LT). Fish were reared in 500 L tanks for 12 weeks, after which growth performance, feed intake, feed conversion ratio (FCR) and health indices were measured. Significant improvements in FCR were observed in the 8 % SB and 16 % SB groups (0.99 and 0.98, respectively), compared to the control diet (1.06). Protein and energy retention were also highest in the 8 % SB and 16 % SB diets, with respective retention efficiencies of 39.0 % and 37.8 %. Apparent digestibility was comparable across diets, with protein digestibility peaking at 87.9 % in the 4 % SB + 4 % LT diet. Histological analysis revealed no significant changes in intestinal or skin integrity. Blood biochemistry, hematology, gene expression profiles and microbiome were unaffected by SCP inclusion, except for a notable decrease in gut bacterial diversity in fish fed the 4 % SB + 4 % LT diet. Overall, these results demonstrate that SCPs, particularly SB at 8 % and 16 % inclusion levels, can effectively replace fishmeal in YTK diets without compromising health or growth, while enhancing feed efficiency and nutrient retention.

Recommended Citation

Luke Pilmer, Gavin Partridge, Chelsea Woods, Md Javed Foysal, Md Reaz Chaklader, Alan Lymbery, Lindsey Woolley, Alternative proteins in Aquafeeds: Evaluating methanotrophic and hydrogenotrophic bacterial meals in yellowtail kingfish diets, Aquaculture, Volume 613, Part 1, 2026, 743371 ISSN 0044-8486. https://doi.org/10.1016/j.aquaculture.2025.743371