Isolation and optimisation of chitin-degrading bacteria from bird faecal waste and its chitinase activity

Chitin-degrading microorganisms play a vital role in nutrient cycling and have significant biotechnological potential. In this study, chitinolytic bacteria were isolated from bird faecal samples using chitin-containing selective media. Six isolates were obtained, among which strain A3 exhibited the highest chitin-degrading activity, as indicated by a prominent clear zone on chitin agar. Morphological, biochemical, and phylogenetic analyses identified the isolate as Enterobacter cloacae . Quantitative estimation of enzyme activity revealed that E. cloacae produced maximum chitinase activity of 5.61 U/mL at 48 h and pH 5.5, indicating that enzyme production is strongly influenced by incubation time and acidic conditions. Medium components affecting chitinase production were screened using the Plackett–Burman design. Chitin, yeast extract, and CaCl₂ were identified as the most significant factors influencing enzyme yield. Further optimisation using the central composite design demonstrated good agreement between actual and predicted chitinase activities, although some deviations were observed at extreme factor levels. The response surface model showed strong fitting (R² = 0.914), but a lower predicted R² indicated limited predictive ability beyond the experimental range. Phylogenetic analysis confirmed the close evolutionary proximity of the isolate to known Enterobacter cloacae strains, validating its taxonomic classification.