Harnessing shrimp shell waste: enhanced chitinase production through optimization techniques for ecofriendly solutions using bacteria

Chitinous wastes, particularly shrimp shell residues, represent a major underutilized biomass resource with significant potential for bioconversion into high-value products. In this study, four thermophilic bacterial strains ( Bacillus amyloliquefaciens BT 2022, Bacillus licheniformis Basma87, Priestia megaterium AMD 2024, and Streptomyces maritimus MSQ-2021) were screened for their ability to produce chitinase using shrimp shell waste (SSW) as the sole carbon and nitrogen source. Among these, P. megaterium AMD 2024 exhibited the highest chitinolytic activity. Optimization of fermentation parameters was initially performed using the one-variable-at-a-time (OVAT) approach, identifying 5% SSW, 60° C, 72 h incubation, pH 7.0, 200 rpm shaking, and 2% inoculum size as optimal conditions, yielding 93.24 U/mL chitinase activity. Subsequent statistical optimization using response surface methodology (RSM) with Plackett–Burman design (PBD) and central composite design (CCD) significantly enhanced enzyme production, achieving maximum activity of 273.3 U/mL, representing a 2.93-fold increase compared to OVAT. Partial purification via ammonium sulphate saturation (60–80%) resulted in 260.0 U/mL activity with 95.13% relative activity. Cytotoxicity assays using normal human skin cell line HFB4 confirmed the biocompatibility of the purified enzyme at concentrations up to 260.0 U/mL. These findings demonstrate that shrimp shell waste can be efficiently valorized into chitinase through microbial fermentation, providing an eco-friendly solution for waste management and offering safe, sustainable applications in agriculture, industry, and cosmetics.