Sonbol Fatma I, Abdel Aziz Ahmed A, El-Banna Tarek E, Al-Fakhrany Omnia M
Microbiology and Immunology, Faculty of Pharmacy, Tanta University, Tanta, 31111, Egypt.
Int Microbiol. 2020 Nov;23(4):533-547. doi: 10.1007/s10123-020-00127-z. Epub 2020 Apr 18.
The increasing mandate for fresh-like food products and the possible hazards of chemically preserved foods necessitate the search for alternatives. Bacteriocins represent a promising food biopreservative. In the present study, one hundred enterococci isolates recovered from Egyptian raw cow milk and homemade dairy products were screened for bacteriocin production. The overall detection rate was 10%. Three isolates, namely, Enterococcus faecalis (OE-7 and OE-12) and Enterococcus hirae (OE-9), showed the highest antibacterial activity with narrow spectrum against multidrug-resistant (MDR) Gram-positive foodborne bacteria: Enterococcus faecalis and Staphylococcus aureus. The antimicrobial activity was completely abolished by trypsin and proteinase K but not affected by lipase and/or amylase indicating the protein nature of the antimicrobial activity. Optimum conditions for bacteriocin production were cultivation in MRS broth at 37 °C, pH 6-6.5 for 16-24 h. The tested bacteriocins exhibited bactericidal activity on S. aureus subsp. aureus ATCC 25923; such activity was further investigated by transmission electron microscopy that revealed leakage and lysis of treated cells. Characterization of tested bacteriocins revealed high activity in a wide range of pH and temperature, storage stability, and heat resistance. PCR analysis revealed that the tested isolates produced multiple enterocins showing homology with the enterocins L50A, AS-48, and 31. Finally, this study reported potent antibacterial activity of bacteriocins derived from dairy products Enterococci against MDR foodborne and spoilage pathogens. The potency, specificity, and stability of these bacteriocins presented promising perspectives for application as biopreservatives in the food industry. The biopreservation of foods by bacteriocins produced by lactic acid bacteria recovered directly from foods remains an innovative approach.
对新鲜类食品的需求不断增加，以及化学防腐剂食品可能存在的危害，使得寻找替代品成为必要。细菌素是一种很有前景的食品生物防腐剂。在本研究中，对从埃及生牛奶和自制乳制品中分离出的100株肠球菌进行了细菌素产生情况的筛选。总体检出率为10%。三株分离株，即粪肠球菌（OE - 7和OE - 12）和平肠球菌（OE - 9），对多重耐药（MDR）革兰氏阳性食源细菌粪肠球菌和金黄色葡萄球菌表现出最高的抗菌活性，且抗菌谱较窄。胰蛋白酶和蛋白酶K可完全消除抗菌活性，但脂肪酶和/或淀粉酶不影响该活性，这表明抗菌活性的本质是蛋白质。细菌素产生的最佳条件是在MRS肉汤中于37℃、pH值6 - 6.5下培养16 - 24小时。所测试的细菌素对金黄色葡萄球菌亚种金黄色葡萄球菌ATCC 25923具有杀菌活性；通过透射电子显微镜进一步研究发现，经处理的细胞出现渗漏和裂解。对所测试细菌素的特性进行表征发现，其在广泛的pH值和温度范围内具有高活性、储存稳定性和耐热性。PCR分析表明，所测试的分离株产生多种与肠球菌素L50A、AS - 48和31具有同源性的肠球菌素。最后，本研究报道了源自乳制品肠球菌的细菌素对多重耐药食源和腐败病原体具有强大的抗菌活性。这些细菌素的效力、特异性和稳定性为其在食品工业中作为生物防腐剂的应用提供了广阔前景。直接从食品中回收的乳酸菌产生的细菌素对食品进行生物保鲜仍然是一种创新方法。
