Abstract
Abstract A total of 544 isolates of lactic acid bacteria isolated from fermented products: 451 isolates from fermented products from Thailand and 93 isolated from French fermented products were screened for bacteriocin production. 10 isolates showed antimicrobial activities. Identification of the selected strains by random amplification of polymorphic DNA-polymerase change reaction using the primers E1, E2 and M13 showed three different RAPD patterns. One of the isolates from each product was chosen and good antimicrobial activity were displayed by 3 strains including MP6/2, PKS2-1 and OV1-1 producing in MRS broth bacteriocin-like substance (BLIS) inhibiting Candida albicans ATCC 90028, Carnobacterium maltraromaticum NCDO 2760, Lactobacillus sakei subsp. sakei JCM 1157, Listeria innocula CIP 80.11, Listeria ivanovii SLCC 2379, Pseudomonasc aeruginosa ATCC 27853, Staphylococcus aureus CIP 76.25 and Streptococcus mutans used as indicator strains. However, inhibitory activities of MP6/2 and PKS2-1 were related to the production of either organic acid, while OV2-1 was not affected by heating. The inhibitory activities of these three isolates were sensitive to proteolytic enzymes. 16S rDNA gene sequencing allowed to identify the MP6/2 as Pediococcus pentosaceus while PKS2-1 and OV1-1 were identified as Enterococcus faecium. It was concluded that the obtained isolates may be used as bio-preservative cultures to produce fermented foods.
Highlights
Nowadays consumers are aware of the composition of their foods and want to avoid chemical preservatives and taste enhancers like monosodium glutamate
The strains were assessed for production of antimicrobial substances by agar overlay method, the occurrence of clear inhibition zones around the colonies indicates that particular Lactic acid bacteria (LAB) colonies can produce some active substance capable of inhibiting the growth of indicator strains, and about 26 isolates were selected with antimicrobial activity (Table S2, and Figure 1A)
The selected ten isolates (MP6/2, PKS2-1, PKS2-2, PKS3-7, PKS3-8, PKS4-2, OV1-1, OV2-3, OV3-4, and OV3-6) showed antimicrobial activity against indicator strains such as B. cereus, C. maltaromaticum NCDO 2760, L. sakei subsp. sakei JCM 1157, L. innocua CIP 80.11, L. ivanovii SLCC 2379, S. aureus CIP 76.25, S. mutans, and C. albicans ATCC 90028 (Table 1)
Summary
Nowadays consumers are aware of the composition of their foods and want to avoid chemical preservatives and taste enhancers like monosodium glutamate. The consumer demands and government regulations push the food manufacturers to find the natural preservatives to control the contaminating microbes, mostly responsible for food spoilage and poisoning. LAB can produce organic substances that are responsible for the unique aroma (Caplice & Fitzgerald, 1999). The LAB is found in fermented products, beverages, milk and even in meat products, are purposely used to prevent the food spoilage and to enhance the quality of the foods like improved flavor and texture. Some of the LAB strains produce antagonistic substances when competing with other microbes in the surroundings. These substances are called bacteriocins or bacteriocin-like inhibition substances (BLIS) (Moreno et al, 2000)
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