Department of Agricultural, Food and Nutritional Science, 4-10 Agriculture Forestry Centre, University of Alberta, Edmonton, Alberta T6G 2P5, Canada.
Faculty of Pharmacy and Pharmaceutical Sciences, 2-35 Medical Sciences Building, University of Alberta, Edmonton, Alberta T6G 2H7, Canada.
Int J Food Microbiol. 2017 Aug 16;255:25-31. doi: 10.1016/j.ijfoodmicro.2017.05.016. Epub 2017 May 24.
The aims of this study were to improve the method for purification of leucocin A to increase yield of peptide and to evaluate the efficacy of leucocin A and an analogue of leucocin A (leucocin N17L) to inhibit the growth of Listeria monocytogenes on wieners in the presence of spoilage organisms. Leucocin A was produced by Leuconostoc gelidum UAL187 and purified with a five-fold increase in yield; leucocin N17L was synthesized replacing asparagine at residue 17 with leucine. Five strains of L. monocytogenes associated with foodborne illness were used to assess bacteriocin efficacy in vitro and in situ. Minimum inhibitory concentrations could not be determined in broth; however, on agar the minimum inhibitory concentrations ranged from 11.7-62.5μM and 62.5->500μM for leucocin A and leucocin N17L, respectively. Leucocin N17L was less effective than the native bacteriocin at controlling the growth of L. monocytogenes. The inactivation profiles of L. monocytogenes in broth in the presence of leucocin A suggested each isolate had different levels of resistance to the bacteriocin as determined by the initial bactericidal effect. The formation of spontaneously resistance subpopulations were also observed for each strain of L. monocytogenes. In situ, wieners were inoculated with the spoilage organisms, Carnobacterium divergens and Brochothrix thermosphacta, followed by surface application of purified leucocin A, and inoculated with a cocktail of L. monocytogenes. Wieners were vacuum packaged and stored at 7°C for 16d. Leucocin A reduced the counts L. monocytogenes on wieners during storage, regardless of the presence of C. divergens. B. thermosphacta was unaffected by the presence of leucocin A on wieners over the duration of storage. This study suggests that leucocin A may be beneficial to industry as a surface application on wieners to help reduce L. monocytogenes counts due to post-processing contamination even in the presence of spoilage organisms. However, further investigation on the ability of L. monocytogenes to form spontaneous resistance to class II bacteriocins on food matrices during prolonged storage is warranted.
本研究的目的是改进纯化亮菌素 A 的方法，以提高肽的产量，并评估亮菌素 A 和亮菌素 A 的类似物（亮菌素 N17L）在存在腐败菌的情况下抑制单增李斯特菌在维也纳香肠上生长的效果。亮菌素 A 由乳酸片球菌 UAL187 产生，并通过产量提高 5 倍进行纯化；亮菌素 N17L 通过用亮氨酸取代残基 17 处的天冬酰胺来合成。使用与食源性疾病相关的 5 株单核细胞增生李斯特菌来评估细菌素在体外和体内的功效。在肉汤中无法确定最小抑菌浓度；然而，在琼脂上，亮菌素 A 和亮菌素 N17L 的最小抑菌浓度范围分别为 11.7-62.5μM 和 62.5->500μM。亮菌素 N17L 对控制单增李斯特菌生长的效果不如天然细菌素。在亮菌素 A 存在的情况下，肉汤中单增李斯特菌的失活曲线表明，每种分离株对细菌素的耐药性水平不同，这是通过初始杀菌效果来确定的。还观察到每种单增李斯特菌自发抗性亚群的形成。在体内，维也纳香肠接种腐败菌，交替微球菌和热死环丝菌，然后表面应用纯化的亮菌素 A，并接种单核细胞增生李斯特菌混合物。维也纳香肠真空包装，在 7°C 下储存 16 天。亮菌素 A 减少了储存过程中维也纳香肠中单增李斯特菌的计数，无论是否存在交替微球菌。在整个储存过程中，热死环丝菌不受维也纳香肠上亮菌素 A 的影响。本研究表明，亮菌素 A 作为表面应用于维也纳香肠，有助于减少由于后处理污染导致的单核细胞增生李斯特菌计数，即使存在腐败菌，这对行业可能是有益的。然而，需要进一步研究在长时间储存过程中，单核细胞增生李斯特菌在食品基质上形成对 II 类细菌素自发抗性的能力。
