Screening and characterization of thermostable protease-producing bacteria isolated from slaughter site soil samples from Southern India

The current study was isolated and identified Bacillus cereus from an animal slaughter site in the South Indian state of Kerala, as a potent additive to detergents for enhancing stain removal efficacy. Identifying the isolates as B. cereus was confirmed through microbial biomass production, biochemical tests, protease-specific activity, and sequencing of the 16S rRNA gene. Following the growth condition optimization, the protease enzyme was extracted from the biomass, exhibiting a protease activity of 72.212 ± 0.235 U/mL. Calcium, magnesium, and sodium positively influenced protease activity under the tested conditions and were negatively impacted by zinc, copper, and iron. The polar solvent dimethyl sulfoxide (DMSO) supported enzyme activity, whereas the non-polar solvents hexane and chloroform completely inhibited it. The highest protease-specific activity of the crude extract following dialysis was 62.997 U/mg. The purified fractions of Sephadex G-100 and DEAE-Sephadex A50 anion exchange columns showed the highest enzyme-specific activity of 193.652 U/mg and 324.004 U/mg, respectively. The addition of crude protease to a generic detergent significantly enhanced its efficacy in removing fabric stains from cotton, polyester, and silk materials. Therefore, the isolated serine protease demonstrates significant potential for industrial applications.