Removal of pathogenic bacteria and nitrogens by Lactobacillus spp. JK-8 and JK-11

The feasibility of using Lactobacillus strains for the simultaneous removal of pathogenic bacteria and nitrogens, with the ultimate aim of application for the improvement of water quality in shrimp farms, was explored. Initially, strains of Lactobacillus spp. JK-8 and JK-11 in shrimp ponds were screened for their ability to remove pathogenic bacteria and nitrogen compounds. At the end of the incubation period in cultures of JK-8 and JK-11, JK-8 had produced 192.8 mM lactic acid and 43.6 mM acetic acid, and the pH of the culture had decreased from 7.0 to 3.8. However, the JK-11 strain produced only small amounts of organic acids, and the pH of the culture decreased from 7.0 to pH 5.4. Pathogen survival following exposure to concentrated cell-free supernatants derived from JK-8 and JK-11 cultures was also investigated. Pathogens were completely removed within 4 min of exposure to either culture supernatant. Cell-free supernatants concentrated from pH-nonadjusted JK-8 cultures and either pH-adjusted or pH-nonadjusted JK-11 cultures demonstrated remarkable antimicrobial activities against target bacteria (e.g., Vibrio parahemolyticus, V. harveyi, Edwardsiella tarda). Scanning electron microscopy analyses revealed perforations in bacterial cells and irregular rod shapes with wrinkled surfaces following incubation with the concentrated supernatants. Both JK-8 and JK-11 cultures facilitated the removal of up to 400 µM NH4+, NO2−, and NO3−. The results of this work are applicable for the simultaneous removal of pathogens and nitrogens from contaminated shrimp farms.