Optimization of fermentation parameters for enhanced protease production by Lactobacillus plantarum Strain KCB4

Abstract

Proteases are among the most commercially important industrial enzymes owing to their extensive applications in the food, pharmaceutical, detergent, leather, and biotechnological industries. The present study investigated the optimization of fermentation parameters for enhanced protease production by Lactobacillus plantarum KCB4, a proteolytic isolate previously recovered and characterized from poultry waste-contaminated soil. Preliminary protease production was carried out by submerged fermentation using modified MRS broth, after which the crude enzyme was partially purified by ammonium sulphate precipitation and dialysis. Protease activity was determined using the casein hydrolysis method, while a one-factor-at-a-time (OFAT) approach was employed to optimize the effects of initial pH, temperature, carbon source and concentration, nitrogen source and concentration, inoculum size, and fermentation period. Pre-optimization studies showed that L. plantarum KCB4 produced 4.754 U/mL of protease. The optimum conditions for enhanced protease production were pH 4.5, 40°C, 2.5% (w/v) banana peel as the carbon source, 2.5% (w/v) soybean waste as the nitrogen source, 5% inoculum concentration, and 48 h fermentation period. Under these optimized conditions, protease production increased from 4.80 U/mL to 5.80 U/mL, representing an approximately 21% improvement in enzyme yield. The results demonstrate that systematic optimization of fermentation variables significantly enhances protease production by L. plantarum KCB4 and highlight the potential of utilizing inexpensive agro-industrial residues such as banana peel and soybean waste as sustainable substrates for cost-effective enzyme production. These findings support the industrial application of L. plantarum KCB4 as a promising microbial source of protease for food and other biotechnological processes.