el-Ziney M G, Debevere J M
Department of Food Technology and Nutrition, Faculty of Agricultural and Applied Biological Sciences, University of Ghent, Belgium.
J Food Prot. 1998 Oct;61(10):1275-80. doi: 10.4315/0362-028x-61.10.1275.
A broad-spectrum reuterin produced during anaerobic fermentation of glycerol by Lactobacillus reuteri strain 12002 was found to be inhibitory and bactericidal for Listeria monocytogenes and Escherichia coli O157:H7. Lyophilized reuterin was prepared by a two-step fermentation process. A batch fermentation in a 15-liter fermentor was applied to produce a maximum biomass of L. reuteri using a modified MRS broth at pH 4.3. Further, harvested cells were used to ferment glycerol (250 mM) under anaerobic conditions. The sensitivity to reuterin of 10 strains of Listeria spp., including 6 strains of L. monocytogenes, and 6 strains of E. coli, including one enterotoxigenic E. coli strains and two enterohemorrhagic E. coli strains, was estimated. Strains of L. monocytogenes were more resistant to reuterin than E. coli strains. In cottage cheese, pH 5.4, L. monocytogenes increased by 0.4 log while E. coli O157:H7 decreased by 0.5 log in 21 days at 7 degrees C; addition of reuterin (50 to 250 units per g) to the cottage cheese reduced the viability of both organisms. The inactivation rate was more pronounced (P < or = 0.05) with E. coli O157:H7 than L. monocytogenes and it was dependent on reuterin concentration. The rate of E. coli O157:H7 population reduction reached to 2, 3, and 6 log cycles by day 7 for reuterin concentrations of 50, 100, and 150 units per g of creamed cottage cheese, respectively. While, 100, 150, and 250 units of reuterin per g caused reductions in L. monocytogenes counts by 2, 5, and greater than 5 log cycles, respectively. In UHT skim milk with 150 units of reuterin per ml, stored at 7 degrees C, the decline in the numbers of L. monocytogenes cells was higher than that in cottage cheese. Milk fat in the range of 0.5 to 3% did not affect the reuterin activity (P < or = 0.05). Addition of 3% salt enhanced the lethal effect of reuterin and diminished the initial population of L. monocytogenes by 4.5 log cycles in three days at 7 degrees C.
研究发现，罗伊氏乳杆菌12002菌株在甘油厌氧发酵过程中产生的一种广谱罗伊氏菌素，对单核细胞增生李斯特菌和大肠杆菌O157:H7具有抑制和杀菌作用。冻干罗伊氏菌素通过两步发酵工艺制备。在15升发酵罐中进行分批发酵，使用改良的MRS肉汤，pH值为4.3，以产生最大量的罗伊氏乳杆菌生物量。此外，收获的细胞用于在厌氧条件下发酵甘油（250 mM）。评估了10株李斯特菌属菌株（包括6株单核细胞增生李斯特菌）和6株大肠杆菌（包括1株产肠毒素大肠杆菌菌株和2株肠出血性大肠杆菌菌株）对罗伊氏菌素的敏感性。单核细胞增生李斯特菌菌株比大肠杆菌菌株对罗伊氏菌素更具抗性。在pH值为5.4的农家干酪中，7℃下21天内，单核细胞增生李斯特菌数量增加了0.4个对数级，而大肠杆菌O157:H7数量减少了0.5个对数级；向农家干酪中添加罗伊氏菌素（每克50至250单位）可降低两种菌的活力。大肠杆菌O157:H7的失活率比单核细胞增生李斯特菌更显著（P≤0.05），且其取决于罗伊氏菌素浓度。对于每克含50、100和150单位罗伊氏菌素的低脂农家干酪，到第7天时，大肠杆菌O157:H7数量减少分别达到2、3和6个对数周期。而每克100、150和250单位的罗伊氏菌素分别使单核细胞增生李斯特菌数量减少2、5和大于5个对数周期。在每毫升含150单位罗伊氏菌素的超高温灭菌脱脂牛奶中，7℃储存时，单核细胞增生李斯特菌细胞数量的下降高于农家干酪。0.5%至3%范围内的乳脂肪不影响罗伊氏菌素活性（P≤0.05）。添加3%的盐可增强罗伊氏菌素的致死作用，在7℃下三天内使单核细胞增生李斯特菌的初始数量减少4.5个对数周期。
