Morphological and structural characterization of chitin as a substrate for the screening, production, and molecular characterization of chitinase by Bacillus velezensis.

The processing of shellfishery industrial wastes is gaining much interest in recent times due to the presence of valuable components. Chitin is one of the valuable components and is insoluble in most common solvents including water. In this study, a novel gram-positive bacterial strain capable of solubilizing chitin was screened from a prawn shell dumping yard. The chitinolytic activity of the isolated strain was observed through the zone of hydrolysis plate assay. The hyper-producing isolate was identified as Bacillus velezensis through the 16S rRNA sequencing technique. The structural and morphological characterization of raw and colloidal chitin preparation was carried out using FTIR, XRD, and SEM analysis. The residual protein and mineral content, degree of polymerization, and degree of acetylation were reported for both raw and colloidal chitin preparations. There was a linear increase in the chitinase activity with an increase in the colloidal chitin concentration. The maximum activity of chitinase was observed as 38.98 U/mL for the initial colloidal chitin concentration of 1.5%. Supplement of additional carbon sources, viz., glucose and maltose, did not improve the production of chitinase and resulted in a diauxic growth pattern. The maximum chitinase activity was observed to be 33.10 and 30.28 U/mL in the colloidal chitin-containing medium with and without glucose as a secondary carbon source, respectively. Interestingly, the addition of complex nitrogen sources has increased the production of chitinase. A 1.95- and 2.14-fold increase in the enzyme activity was observed with peptone and yeast extract, respectively. The chitinase was confirmed using SDS-PAGE, native PAGE, and zymograms. The optimum pH and temperature for chitinase enzyme activity were found to be 7.0 and 44 °C, respectively.