1株具广谱抑菌活性的乳酸乳球菌的分离鉴定与保鲜效果

Isolation,identification of a Lactococcus lactis strain exhibiting broad-spectrum antibacterial activity and its effects on preservation of chilled pork

为开发出新型冷却肉保鲜剂,从土壤中分离到1株具有较宽抑菌谱的乳酸菌,对冷却肉上7种常见的腐败和致病菌有明显的抑菌活性,包括热死环丝菌、单增李斯特菌、金黄色葡萄球菌、乳酸乳球菌、荧光假单胞菌、致病性大肠杆菌和沙门氏菌,并且排除了因产乳酸和过氧化氢而具备抑菌作用的可能性。根据细胞形态、菌落形态、生理生化反应特性和16Sr DNA序列和具菌株特异性的N-乙酰胞壁酸水解酶基因序列的比对分析,这株菌被鉴定为乳酸乳球菌乳酸亚种(Lactococcus lactis subsp.lactis),命名为NFL。菌株NFL发酵液中的抑菌物质对热有极强的耐受性,在121°C的灭菌温度下处理90 min抑菌活性基本不变。经121℃下灭菌20 min的菌株NFL发酵上清液对托盘包装冷却猪肉具有明显的保鲜效果,尤其是可显著减少腐臭味。

To develop a new type of chilled pork preservative, we isolated a strain from forest soil, which exhibi- ted a broad bactericidal activity against seven spoilage and food-borne pathogens bacteria commonly related to pork, including Brochothrix thermosphacta, Listeria monocytohenes, Staphyloccocus aureus, Lactococcus lactis, Pseudomonas fluorescens, pathogenic Escherichia coli and Salmonella paratyphi. We ruled out the inhibition due to lactic acid and hydrogen peroxide. We further studied the individual and colony morphology features, physiological and biochemical characteristics, the sequence features of the 16S rDNA and the species-specific N-acetylmuraminidase gene （acmA） of this strain. Consequently, it was identified as Lactococcus lactis subsp, lactis, named as NFL. Uniquely, the inhibitory agent was thermally stable up to 121℃ for 90 min. Fermentation filtrate of strain NFL sterilized at 121℃ for 20 min had obvious fresh-keeping effect on chilled pork with tray package, especially significantly reduced rancidity. So, Lactococcus lactis NFL was a potential food preservative-producing strain, especially for chilled pork and pork products fresh-keeping.