Evaluation of Methanotroph (Methylococcus capsulatus, Bath) bacteria meal on body composition, lipid metabolism, protein synthesis and muscle metabolites of Pacific white shrimp (Litopenaeus vannamei)

A feeding trial was conducted to evaluate a new dietary protein Methanotroph (Methylococcus capsulatus, Bath) bacteria meal (BPM) on nutritional profile of Litopenaeus vannamei. The basal diet was formulated to contain 25% fish meal and then 15%, 30% and 45% of fish meal protein were replaced with BPM in three experimental diets, which were labeled FM, BPM15, BPM30, and BPM45, respectively. A total of 480 uniform-sized shrimp were equally distributed to four groups with three replicates and fed experimental diets four times daily for seven weeks. Results showed that dietary BPM had no significant effect on the growth performance of shrimp (P 0.05) but significantly reduced the crude lipid content of the whole body in shrimp fed the BPM30 diet compared to the FM diet (P < 0.05). Total cholesterol and triglyceride in the hemolymph fell significantly with the increase BPM substitution (P < 0.05). Expression of fas (fatty acid synthetase) significantly decreased with increasing BPM substitution, but the expression of cpt-1 (carnitine palmitoyltransferase) significantly increased in shrimp fed BPM30 (P < 0.05). Expression of tor (target of rapamycin) significantly decreased in hepatopancreas, while an opposite change was exhibited in the intestine of shrimp fed BPM45 (P < 0.05). Results of metabolomics indicated that dietary BPM affected the TCA cycle, ascorbate and aldarate metabolism, and glutathione meta-bolism in shrimp. In conclusion, BPM is an alternative to FM as a novel protein source for shrimp feed, but the changes in whole body composition, lipolysis and fatty acid synthesis, and protein synthesis and muscle me-tabolites of L.vannamei are noted.