Antibacterial and technological properties of Lactobacillus plantarum strains isolated from oranges and artisanal fruit salads

L.V. RIVERO, M.R. MORALES, F.M. SAGUIR

Mendoza

Congreso; LVI Reunión Anual SAIB + Reunión Anual SAMIGE; 2020

SAIB-SAMIGE

Lactic acid bacteria (LAB) can rapidly acidify food through the organic acids production, thus, extending shelf life and improving the safety and quality of fermented food. Many consumers, in particular vegans and lactose-intolerant individuals, are increasingly interested in consuming non-dairy LAB food products. In a previous study, six Lactobacillus plantarum strains isolated from orange and artisanal fruit salads were selected by their lactic potential and antagonistic activity in in vitro tests. The objective of this work was to evaluate the inhibitory effect of L. plantarum N8, JNB25, EFj18, EFj24, EFj47, EFf29 against common bacterial pathogens when inoculated in a commercial multi-fruit juice (CMJ) as well as some interest technological properties (antimicrobial susceptibility, amine biogenic production, biofilm inhibition). CMJ was sterilized in autoclave (121°C, 5 min) before inoculating with each test pathogen and/or LAB strain. Uninoculated CMJ was used as control. BIOCELL xxxx (suppl. xxx), 2020 ABSTRACTS ISSN 0327- 9545 L01 / SB-P03-209 ISSN 1667-5746 (online version) Control and test juices were incubated at 37°C during 72 h. For antimicrobial susceptibilities assay, minimum inhibitory concentrations (MICs) against chloramphenicol, erythromycin, tetracycline, amoxicillin, and ciprofloxacin at 2.0, 4.0, 8.0, 16, 32, 64, 128 μg/mL was determined. Biogenic amines (AB) production was qualitatively evaluated using minimal decarboxylase medium supplemented with lysine, ornithine, histidine, tyrosine, or arginine (0.1%, w/v), while biofilm formation inhibition was assayed with the violet crystal method. In general, all LAB tested grew in inoculated juice between 1.0?2.0 log CFU/mL during the first two days, then remained viable until 72 h. At this time, pH declined of about 0.45?0.50 units depending on the strain. In this condition initial population of S. typhimurium (order 107 CFU/mL) remained unchanged for 12 h, without detecting viable cells at 24 h. When co-inoculated with each LAB increased its inactivation rate except for strains EFJ24 and EFJ47. In juice inoculated with L. monocytogenes, its initial population was reduced ~3.0 log at 12 h, however, in presence of L. plantarum N8 and EFJ18 it was completely inactivated. Most of the LABs strains were sensitive to the antibiotics tested, especially tetracycline, ciprofloxacin, and chloramphenicol, while none of the strain showed potential for producing BA except from arginine and, all of them inhibited biofilm formation in a range of 53 to 64% for both pathogens tested. In conclusion, all L. plantarum strains were effective to inactivate bacterial pathogens in CMJ, although with variations strain-specific while all exhibited good technological properties, being good candidates to be used in elaboration of safety fermented fruit juices.