Production, optimization, characterization, and application of chitinase from Bacillus proteolyticus isolated from the rhizosphere of diseased arecanut palm.

Chitin, a polysaccharide composed of β1,4-linked N-acetyl-D-glucosamine, is degraded by chitinases into chitosan oligosaccharides or N-acetyl-D-glucosamine. Chitosan is a deacetylated derivative of chitin, produced by the removal of acetyl groups from the chitin polymer chain, and is widely used in biomedical, agricultural, food, environmental, and nanotechnology applications. Plant growth-promoting rhizobacteria (PGPR) enhance plant growth by facilitating nutrient uptake, modulating hormones, and acting as biocontrol agents against pathogens. This study focuses on the screening, production, partial purification, characterization, and application of chitinase enzymes from Bacillus proteolyticus, a potential isolate obtained from a completely depleted Arecanut plantation, with enzyme activity optimized under both submerged and solid-state fermentation. The highest chitinase yield was obtained through solid-state fermentation at 25.03 U/ml/min, compared to 20.23 U/ml/min in submerged fermentation. Consequently, solid-state fermentation was employed to produce chitinase using different substrates. Among the substrates tested—rice bran and wheat bran—wheat bran supported higher enzyme activity. Chitinase produced from wheat bran was partially purified, resulting in a 2.5-fold increase in purity. Maximum enzyme activity was observed at pH 7 and 30 °C, with dextrose as the carbon source and beef extract as the nitrogen source. The partially purified chitinase exhibited a molecular weight of 25 kDa and demonstrated chitobiose activity by hydrolyzing 4-Methylumbelliferyl N-acetyl-β-D-glucosaminide (4-MUF-GlcNAc). Additionally, the enzyme showed antifungal activity against the phytopathogens Colletotrichum sp. and Alternaria sp.