Effects of different drying methods on bioactivity of cell-free supernatant from Lactiplantibacillus plantarum

In this study, the antibacterial properties of Lactiplantibacillus plantarum (LP) free cell supernatant dried using different coating materials (maltodextrin-M and sodium caseinate-K) and drying techniques (spray-drying-S and freeze-drying-F) on fish spoilage and pathogenic bacteria were investigated. Significant differences were observed in the morphological structures of microencapsulated and non-microencapsulated lyophilised and spray-dried samples (p<0.05). Samples covered with coating material that were spray-dried showed a spherical shape, whilst samples that were freeze-dried developed smooth sheets that resembled plates. The highest inhibition effect against bacteria among the groups was observed in freeze-dried L. plantarum supernatant coated with sodium caseinate (FKLP). The highest inhibition zone against S. aureus, a gram positive foodborne pathogen, was found in the control LP and FKLP groups with values of 24.67 and 23.67 mm, respectively. The lowest inhibition zone diameter for Vibrio vulnificus and Photobacterium damselae was observed in the SLP group (11.50 and 12.00 mm, respectively), while for Proteus mirabilis growth, it was observed in the SMLP group (7.50 mm). The bacteriostatic concentration of the unencapsulated crude LP group was 50 mg/mL for S. aureus, Vibrio vulnificus, and Photobacterium damselae. The bactericidal concentration of the supernatants against foodborne pathogens was 50 mg/mL for Staphylococcus aureus. The bactericidal concentration of the supernatants against foodborne pathogens was above 100 mg/mL except for the FKLP group (100 mg/mL) for S. aureus.