Twenty samples of Brazilian meat and meat products were screened by the agar overlay method for bacteriocinproducing lactic acid bacteria, using Lactobacillus sake ATCC 15521 as indicator strain. Based on Gram staining, KOH reaction, catalase test and fermentation of 49 carbohydrates (API 50 CH), three out of seven isolates with confirmed antagonist properties were identified as Lactobacillus curvatus, one as Leuconostoc mesenteroides and one as Leuconostoc sp. Two isolates could not be properly identified using these tests. The inhibitors produced by these strains were sensitive to proteases. Inhibition due to lytic bacteriophages was ruled out, so the isolates were classified as bacteriocin-producing lactic acid bacteria. Four of them presented antilisterial activity and a potential application as biopreservatives in meat systems.
As bactérias láticas (LAB) despertam interesse devido ao seu potencial de utilização no biocontrole em alimentos. Elas podem exercer atividade inibitória frente a outras bactérias devido à competição direta por nutrientes e pela produção de compostos antagonísticos como ácidos orgânicos, diacetil, peróxido de hidrogê-nio e bacteriocinas [3,4,10,21].Até o momento, a nisina é a única bacteriocina permitida para uso em cerca de 50 países [5], incluindo o Brasil onde ela é aprovada para uso em todos os tipos de queijos, e também aplicada na superfície externa de salsichas de diferentes tipos [1,2,16].Entretanto, seu uso em carnes pode ser limitado por interações com esse tipo de alimento [8,25], e até inativação pela enzima glutationa S-transferase de mús-culo bovino [23].Neste trabalho, foram caracterizadas algumas propriedades de bacteriocinas de bactérias láticas. -MATERIAIS E MÉTODOS -Linhagens bacterianasForam estudadas seis linhagens de bactérias láticas isoladas a partir de produtos cárneos brasileiros [7]. A origem e a identificação das referidas cepas estão mostradas na Tabela 1. TABELA 1. Linhagens bacteriocinogênicas estudadas neste trabalho. CARACTERIZAÇÃO PRELIMINAR DE BACTERIOCINAS PRODUZIDAS POR SEIS CEPAS DE BACTÉRIAS LÁTICAS ISOLADAS DE PRODUTOS CÁRNEOS EMBALADOS A VÁCUO SUMMARYPRELIMINARY CHARACTERIZATION OF BACTERIOCINS PRODUCED BY SIX LACTIC ACID BACTERIA STRAINS ISOLATED FROM VACUUM-PACKAGED MEAT PRODUCTS. In this work, the bacteriocins produced by six bacterial strains were studied (Lactobacillus sake 1, Lactobacillus curvatus 5, Leuconostoc mesenteroides 11, Leuconostoc sp 12, Lactobacillus curvatus 14 and Lactobacillus sake 16). Title of inhibitory activity was determined by critical dilution assay, using Lactobacillus sake ATCC 15521 and Listeria monocytogenes as indicator microorganisms. The inhibitory compounds were also characterized with respect to stability to the action of enzymes, thermostability, stability in several pHs and mode of action (bactericide or bacteriostatic) towards Listeria monocytogenes. No bacteriocin was destroyed by pepsin, but all of them were destroyed by proteinase K, trypsin and α-amylase (except that α-amylase did not inactivate the bacteriocin produced by Leuconostoc sp 12). Lactobacillus sake 1, Leuconostoc mesenteroides 11 and Lactobacillus sake 16 exerted antilisterial activity. The more active strains against Listeria monocytogenes were Lactobacillus sake 1 and Leuconostoc mesenteroides 11 (12.800 AU/ml). Bacteriocins produced by Lactobacillus sake 1 and Lactobacillus curvatus 5 presented the highest thermal stability. The bacteriocin of Lactobacillus sake 1 was the most stable to pH variations. All LAB produced bacteriocin in the range of temperature from 4 o C to 30 o C and this property is of great interest for future applications in refrigerated meat products.
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