Lactobacillus plantarum ST202Ch and Lactobacillus plantarum ST216Ch – What are the Limitations for Application?

Lactobacillus plantarum ST202Ch and Lactobacillus plantarum ST216Ch, isolated from Beloura and Chourico (Portuguese fermented meat products), produced bacteriocins active against a number of Gram-positive and Gram-negative meat spoilage bacteria and Mycobacterium tuberculosis. In addition, Lb. plantarum ST202Ch and Lb. plantarum ST216Ch presented a good potential to be considered as probiotic candidates based on the genetic and physiological tests. However, before using both strains as biopreservatives and probiotic cultures, other investigations are in progress to assess their safety and virulence traits potentially hindering their applications in meat production processes. This work first screened both Lb. plantarum strains for the occurrence of several bacteriocin genes. Lb. plantarum ST202Ch generated positive results for the presence of pediocin PA-1 genes and no evidences for nisin, plantaricin S, plantaricin W and plantaricin NC8. On the other hand, Lb. plantarum ST216Ch gave no evidences for all the bacteriocins genes targeted in this study. Bacteriocins produced by Lb. plantarum ST202Ch and Lb. plantarum ST216Ch have been partially purified by ammonium sulphate precipitation and hydrophobic chromatography on SepPakC18 column. Semipurified bacteriocins presented a very high activity against Listeria monocytogenes, Staphylococcus aureus and Enterococcus faecalis. However, when semi-purified bacteriocin ST202Ch and bacteriocin ST216Ch (fraction 40% iso-propanol in 25 mM phosphate buffer, pH 6.5) at 50 μg/mL protein concentration have been tested for cytotoxicity, only 56.1% and 65.8% survival of human hepatocytes cells (Huh7.5) were recorded. At lower protein concentration (25 μg/mL), the bacteriocins were not cytotoxic. Based on these results, cytotoxicity of bacteriocin ST202Ch and bacteriocin ST216Ch corresponded to CC50 of about 50-100 μg/mL. According to these preliminary results, Lb. plantarum ST202Ch and Lb. plantarum ST216Ch could be used as biopreservatives cultures in meat production processes. However, further in vitro and in vivo investigations are needed towards their applications as probiotics.