Isolation and Characterization of Chitinase-Producing Bacteria in Mangrove Crabs (Scylla sp.) with Loose Shell Syndrome

Mangrove crabs (Scylla spp.) are ecologically and economically important in coastal regions, particularly in Philippine aquaculture. A novel loose shell syndrome threatens these crab populations, yet its etiology remains unclear. With chitin as essential exoskeletal component in crustaceans, the study aimed to screen, isolate and characterize chitinase-producing bacteria in mangrove crabs affected with loose shell syndrome (LSS). Five mangrove crab samples were procured from the province of Capiz in central Philippines and immediately transported to the laboratory. Homogenized and serially diluted guts, gills, and carapace scrapings were spread-plated onto nutrient agar (NA) media supplemented with 1% NaCl. Subsequently, the isolates were subcultured onto NA plates containing 1% powdered chitin and 1% NaCl to screen for chitinase-producing bacteria. Five isolates showing the highest chitinolytic index values were subjected to further characterization via morphological and biochemical assays, whereas molecular identification was conducted by sequencing the 16S rRNA gene. Molecular analysis identified the chitinolytic bacteria as belonging to the putative genera Vibrio, Shewanella, and Brevundimonas. The findings of the study suggest a potential link between chitinase-producing bacteria and loose shell syndrome, opening avenues for deeper exploration into its underlying causes and the development of targeted interventions that ensure sustainable aquaculture practices for this commercially important species.