Studies on the behavior of Listeria monocytogenes and its control in fishery products

研究了单核细胞增生李斯特菌在水环境和水产品中的行为，以及生物保藏技术对水产品中单核细胞增生李斯特菌控制的适用性。在水环境中，在营养盐污染程度较高的河流中检出了单核细胞增生李斯特菌。在海水中，单核细胞增生李斯特菌在较低温度下能维持较长时间的可培养状态，也可能进入活的但不可培养（VBNC）状态。在海水等营养条件下，单核细胞增生李斯特菌细胞对某些胁迫的抵抗力比新鲜培养的细胞更强，接种于某些发酵水产品中，其在贮藏过程中的数量下降，这与贮藏温度、产品成分和乳酸菌的含量有关。从冷冻鱼糜中分离到一批乳酸菌，并对其进行了单增李斯特菌生长抑制菌的筛选。鱼生肉杆菌CS526产生一种新的IIa类细菌素-鱼霉素CS526，其分子量为4，430 Da，在N-末端具有独特的氨基酸序列YGNGL。Carnobacterium sp.Sur602产生的细菌素样物质依赖于培养基中酪蛋白的浓度。鱼霉素CS526扰乱了细胞质膜的功能，从而对单核细胞增生李斯特菌产生了杀伤作用，同时伴随着K^+离子的外排、膜电位的耗散和细胞内ATP的快速消耗。鱼生梭菌CS526对冷熏鲑鱼中单核细胞增生李斯特菌的生长具有抑制作用。细菌素及其生产者可能具有潜在的渔业产品对单核细胞增生李斯特菌的生物保护。

Behavior of Listeria monocytogenes in aquatic environment and fishery products, and applicability of biopreservation to control of L.monocytogenes in the products were investigated. In aquatic environment, L.monocytogenes was detected in a river with higher nutritional pollution. In seawater L.monocytogenes maintained the culturable state longer at lower temperature and also might enter a viable but nonculturable (VBNC) state. In nutritionally weak condition like seawater, L.monocytogenes cells became more resistant against some stresses than freshly cultured cells.Inoculated in some fermented fishery products, L.monocytogenes decreased during storage, which was affected by storage temperature, ingredients and inclusion of lactic acid bacteria in the products. As a result of screening for bacteria inhibiting growth of L.monocytogenes, some strains of lactic acid bacteria were isolated from frozen surimi. Carnobacterium piscicola CS526 produced a novel class IIa bacteriocin, piscicocin CS526, which had a molecular mass of 4,430 Da and a unique amino acid sequence of YGNGL at the N-terminal. Carnobacterium sp.Sur602 produced bacteriocin-like substances depending on casein concentration in the medium. The piscicocin CS526 perturbed functions of the cytoplasmic membrane to act bactericidally against L.monocytogenes accompanied with the efflux of K^+ ions, dissipation of membrane potential, and rapid depletion of intracellular ATP. C.piscicola CS526 was effective to inhibit growth of L.monocytogenes in cold-smoked salmon. Bacteriocin and its producer might have potential for biopreservation of fishery products against L.monocytogenes.