Recombinant <i>Bacillus subtilis</i> Improves Growth and Protein Utilization and Regulates PI3K/AKT/TOR Pathway-Related Genes in Chinese Mitten Crab (<i>Eriocheir sinensis</i>)
The inclusion of suitable quantities of plant protein hydrolysates in feed enhances the growth performance of aquatic animals, a benefit closely linked to the bioactive peptides generated during plant protein hydrolysis. In our previous study, we developed a recombinant <i>Bacillus subtilis<...
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| Main Authors: | , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
MDPI AG
2025-06-01
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| Series: | Animals |
| Subjects: | |
| Online Access: | https://www.mdpi.com/2076-2615/15/12/1732 |
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| Summary: | The inclusion of suitable quantities of plant protein hydrolysates in feed enhances the growth performance of aquatic animals, a benefit closely linked to the bioactive peptides generated during plant protein hydrolysis. In our previous study, we developed a recombinant <i>Bacillus subtilis</i> expressing the P4’ peptide of cottonseed meal (P4’ peptide-bearing <i>B. subtilis</i>). We observed that the addition of this recombinant <i>B. subtilis</i> at a dose of 10<sup>9</sup> CFU/kg to the diet of <i>E. sinensis</i> produced a significant growth-promoting effect. The mechanism underlying this growth-promoting effect remains unclear. This experiment aimed to investigate the effects of feed supplementation with P4’ peptide-bearing <i>B. subtilis</i> on the growth performance, digestive enzyme activities, serum protein content, antioxidant-related enzyme activities, and genes associated with the PI3K/AKT/TOR pathway in the Chinese mitten crab (<i>Eriocheir sinensis</i>). A total of 240 crabs (mean body weight: 0.85 ± 0.01) were randomly assigned to three groups and provided with three distinct diets: one without <i>B. subtilis</i> (CON), one containing 10<sup>9</sup> CFU/kg of unmodified <i>B. subtilis</i> (BS9), and one with P4’ peptide-bearing <i>B. subtilis</i> (RBS9) at 10<sup>9</sup> CFU/kg. After 8 weeks of feeding, the BS9 and RBS9 groups had significantly increased specific growth rate, average body weight, muscle crude protein content, hemolymph total protein/albumin/globulin levels, hepatopancreatic digestive enzyme (protease and amylase) activities, and <i>tor</i> expression in crabs compared to the CON group. Conversely, muscle water content, hepatopancreatic ROS levels, and <i>4ebp-1</i> expression were significantly reduced. Furthermore, mean body weight, protein retention, muscle crude fat content, total hemolymphatic protein, and globulin content, as well as the hepatopancreatic expression of <i>pi3k</i>, <i>tor</i>, and <i>s6k1</i>, were significantly higher in the RBS9 group compared to the BS9 group. In contrast, the hepatopancreatic ROS level exhibited a declining trend. The result demonstrated that compared to unmodified <i>B. subtilis</i>, incorporating 10<sup>9</sup> CFU/kg P4’ peptide-bearing <i>B. subtilis</i> into the feed significantly enhanced the growth performance and protein deposition in <i>E. sinensis</i>. This enhanced effect coincided with the upregulation of key PI3K/AKT/TOR pathway genes (<i>pi3k</i>, <i>tor</i>, <i>s6k1</i>) and the downregulation of <i>4ebp-1</i> in the hepatopancreatic cells, indicating a potential role of this pathway in mediating the observed growth promotion. |
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| ISSN: | 2076-2615 |