Evaluating the Chitosan Extracted From Black Soldier Fly Larvae (BSFL) in Modulating Gut Microbiota of Freshwater Giant Prawn, Macrobrachium rosenbergii

Chitosan is a biopolymer popularly used as a functional feed additive. There are various sources of chitosan, including black soldier fly larvae (BSFL). This study aimed to evaluate the potential of BSFL‐derived chitosan in the modulation of intestinal microbiota in Macrobrachium rosenbergii . The prawns were randomly distributed into four groups, and the diets supplemented with chitosan at levels viz., 0 g/kg (control [ C ]), 2 g/kg shrimp shell chitosan ( T 1), 2 g/kg BSFL chitosan ( T 2), and 4 g/kg BSFL chitosan ( T 3) were fed for 90 days. In terms of growth performance, the T 3 group exhibited significantly the highest weight gain (WG) (%) (470.10 ± 24.90), and upregulation of antioxidant immune genes sod and cat , compared to the other treatment groups. The 16S rRNA amplicon sequencing was performed on the prawn gut samples. The T3 had a significantly higher abundance of phyla Firmicutes (33%), Bacteroidota (2.2%), genus Chitinibacter (11.3%), and Clostridium (2.5%) compared to the control. The T 3 also had higher indices of alpha diversity compared to other groups. The T 3–control comparison exhibited the highest dissimilarity coefficient (0.118). The unweighted pair‐group method with arithmetic mean (UPGMA) results indicated clustering among treatment groups. The analysis of similarity (Anosim), multiresponse permutation procedure (MRPP), ADONIS, and metagenomeSeq analyses confirmed a significant community difference (phylum Bacteroidota, genus Clostridium , and Chitinibacter ) between the control and T 3 groups. The linear discriminant analysis effect size (LEfSe) revealed potential biomarkers, and T 3 exhibited the highest linear discriminant analysis (LDA) scores for order: Burkholderiales, family: Chitinibacteraceae, genus : Chitinibacter , and order: Clostridiales, family: Clostridiaceae, genus: Clostridium . The pathways related to biosynthesis, metabolism, signaling, and cellular processes were higher in T 3, thus contributing to better growth. This study suggested that BSFL chitosan at 4 g/kg diet modulates and enhances beneficial bacteria in the gut of M. rosenbergii and promotes growth and immunity.