Characterization of protease produced by Lactobacillus plantarum strain KCB4

Proteases are among the most important industrial enzymes owing to their extensive applications in the food, feed, pharmaceutical, detergent, leather, and biotechnological industries. The industrial value of these enzymes depends not only on high production yield but also on their biochemical properties and catalytic stability under different processing conditions. This study aimed to characterize the partially purified extracellular protease produced by Lactiplantibacillus plantarum KCB4 following optimization of fermentation conditions. The organism was cultivated under previously optimized conditions using banana peel and soybean waste as carbon and nitrogen sources, respectively. The crude enzyme was recovered, partially purified by 90% ammonium sulphate precipitation, desalted by dialysis, and assayed using casein as the substrate. The biochemical properties of the enzyme were evaluated by determining its optimum temperature and pH, thermal and pH stability, and hydrolytic activity on soybean meal. The protease exhibited maximum activity of 8.1 U/mL at 37 °C and retained appreciable activity up to 77 °C, indicating moderate thermostability. Optimum enzyme activity was recorded at pH 8 (6.5 U/mL), while maximum pH stability was observed at pH 7, with the enzyme retaining high residual activity between pH 7 and 9. The protease also demonstrated strong hydrolytic activity on soybean meal, recording 31.6 U/mL, indicating efficient degradation of soybean proteins. These findings demonstrate that the extracellular protease produced by Lactiplantibacillus plantarum KCB4 possesses desirable catalytic properties, broad operational stability, and considerable hydrolytic potential, making it a promising candidate for applications in food processing, feed improvement, and other industrial biotechnological processes.