ANTIMICROBIAL ACTIVITY OF LACTIPLANTIBACILLUS AND LEVILACTOBACILLUS STRAINS ISOLATED FROM FERMENTED OLIVE AND THEIR APPLICATION IN MILK AND PASTILLA LEAF BIOPRESERVATION

Abstract

Biological preservatives are increasingly in demand as an alternative to chemicals, because of consumer’s health and environmental concerns. Lactic acid bacteria isolated from fermented olives, considered as extreme environment, may encompass significant antimicrobial activity against microorganisms involved in foodborne diseases and food spoilage. Three LAB strains (Levilactobacillus brevis S27, Lactiplantibacillus pentosus S42, and Lactiplantibacillus plantarum S62), isolated from fermented olive, were studied for their antimicrobial activity against pathogenic bacteria (Listeria innocua and E. coli) and yeast (Rhodotorula glutinis), involved in foodborne diseases and food spoilage. The microbial culture, cell-free supernatant (CFS) of all LAB strains showed inhibition zone (IZ) values ranges of 26.33-28.83 mm, 14.16-16.33 mm and 10-12.16 mm against R. glutinis, L. innocua and E. coli, respectively. The IZ values ranges obtained with NCFS (neutralized CFS at pH 7) against R. glutinis and L. innocua were respectively of 17.83-20.50 mm and 13.16-14.50 mm, whereas no inhibition was obtained against E. coli. Their bioactive molecules of proteinaceous nature showed that among the four peptide bands obtained, two bands of approximately 42 and 56 kDa are common for the three LAB strains (S27, S42 and S62). Two additional bands of 46 and 89kD are observed in S42 and S27, respectively. The minimum inhibitory concentration of 10-fold concentrated CFS (10xCFS) obtained was 5% against E. coli and 4.5% against L. innocua and R. glutinis. The 10xCFS of Lb. plantarum S62, selected as the most efficient strain against pathogens, demonstrated its effectiveness in decontamination of milk at concentrations of 0.45% (v/v) and 0.5% (v/v) against L. innocua and E. coli. The CFS allowed, at 0.5 mL/piece of 5 cm diameter, a total inhibition of R. glutinis, without affecting the color of Pastilla leaf. The CFS of Lb. plantarum S62 can be used as a bio-preservative against pathogenic bacteria (L. innocua and E. coli) in milk, and against R. glutinis in Pastilla leaf.