Antimicrobial activity of Goat Milk Casein generated by Lactic Acid Bacteria used against Cronobacter Sakazakii
Cronobacter sakazakii is a foodborne pathogen that has been implicated to be the main cause of neonate’s infections from reconstituted powdered infant formula and powdered milk. Attention is being focused on production of physiologically active compounds derived from milk proteins with antimicrobial...
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| Format: | Thesis |
| Language: | English |
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| Summary: | Cronobacter sakazakii is a foodborne pathogen that has been implicated to be the main cause of neonate’s infections from reconstituted powdered infant formula and powdered milk. Attention is being focused on production of physiologically active compounds derived from milk proteins with antimicrobial property that are effective against the foodborne pathogens are increasing. This study was carried out to investigate the capabilities of 30 lactic acid bacteria (LAB) isolates obtained from different sources to hydrolyse goat’s milk casein (GMC) and produce peptides with antimicrobial activity that can inhibit the growth C. sakazakii and other pathogens. Eight isolates showed good proteolytic activity with clear zones ranging from 7 to 12 mm on skim milk-MRS agar. Initial screening of GMC fermented with these LAB isolates showed that three of them produced hydrolysates that showed antimicrobial activity against the target pathogens C. sakazakii ATCC 25944, C. sakazakii E4 and C. sakazakii O531G and other pathogens. The three LAB were identified as Lactobacillus casei CF2, Enterococcus faecium F.F.B, and Lactobacillus plantarum S by bio-chemical tests, API CHL50, and 16s DNA sequencing. The inhibitory activity of goat milk casein hydrolysate (GMCH) against multi antibiotic resistant pathogens were significantly (P<0.05) affected by LAB isolates, fermentation time, and concentration of GMCH. Killing of target pathogen was observed within 2 h at 0.7 % GMC (v/v). Amino acid profiles of the GMCH varied in the concentration and types of amino acids depending on the LAB used to hydrolyse the GMC. The main amino acid present in the three LAB-GMCH was lysine. The lysine to arginine ratio of GMCH using L. casei-CF2 was 100:0, E. faecium-F.F.B was 91.3: 4.54, L. plantarum-S was 87: 1.58. The ratio of hydrophilic to hydrophobic amino acid of the GMCH also varies with the organism used to generate the peptides. The amino acid profile of the GMCH consisted of hydrophilic amino acid: 69.69% for L. casei-CF2- GMCH, 86.95% for E. faecium-F.F.B-GMCH and 79.68% for L. plantarum-S-GMCH. The results of this study showed potential antimicrobial activity against C. sakazakii by peptides generated from goat milk casein by LAB. |
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