Foulquié Moreno M R, Rea M C, Cogan T M, De Vuyst L
Research Group of Industrial Microbiology, Fermentation Technology and Downstream Processing (IMDO), Department of Applied Biological Sciences, Vrije Universiteit Brussel (VUB), Pleinlaan 2, B-1050, Brussels, Belgium.
Int J Food Microbiol. 2003 Feb 25;81(1):73-84. doi: 10.1016/s0168-1605(02)00167-8.
Two strains, Enterococcus faecium RZS C5 and E. faecium DPC 1146, produce listericidal bacteriocins, so-called enterocins. E. faecium RZS C5 was studied during batch fermentation in both a complex medium (MRS) and in milk to understand the influence of environmental factors, characteristic for milk and cheese, on both growth and bacteriocin production. Fermentation conditions were chosen in view of the applicability of in situ enterocin production during Cheddar cheese production. Enterocin production by E. faecium RZS C5 in MRS started in the early logarithmic growth phase, and enterocin activity decreased during the stationary phase. The effect of pH on enterocin production and decrease of activity was as intense as the effect on bacterial growth. Higher enterocin production took place at pH 5.5 compared with pH 6.5. The use of lactose instead of glucose increased the production of enterocin, and at higher lactose concentration, production increased more and loss of activity decreased. The production in skimmed milk compared to MRS was lower and was detected mainly in the stationary phase. When casein hydrolysate was added to the milk, enterocin production was higher and started earlier, indicating the importance of an additional nitrogen source for growth of E. faecium in milk. For co-cultures of E. faecium RZS C5 with the starters used during Cheddar cheese manufacture, no enterocin activity was detected during the milk fermentation. Furthermore, the applicability of E. faecium RZS C5 and E. faecium DPC 1146 strains was tested in Cheddar cheese manufacture on pilot scale. Enterocin production took place from the beginning of the cheese manufacturing and was stable during the whole ripening phase of the cheese. This indicates that both an early and late contamination of the milk or cheese can be combated with a stable, in situ enterocin production. The use of such a co-culture is an additional safety provision beyond good manufacturing practices.
屎肠球菌RZS C5和屎肠球菌DPC 1146这两种菌株可产生具有杀李斯特菌作用的细菌素，即所谓的肠球菌素。研究了屎肠球菌RZS C5在复合培养基（MRS）和牛奶中的分批发酵过程，以了解牛奶和奶酪特有的环境因素对其生长和细菌素产生的影响。鉴于在切达干酪生产过程中原位产生肠球菌素的适用性，选择了发酵条件。屎肠球菌RZS C5在MRS中产生肠球菌素始于对数生长早期，在稳定期肠球菌素活性下降。pH对肠球菌素产生和活性下降的影响与对细菌生长的影响一样强烈。与pH 6.5相比，在pH 5.5时肠球菌素产量更高。用乳糖代替葡萄糖可增加肠球菌素的产量，在较高乳糖浓度下，产量增加更多且活性损失减少。与MRS相比，脱脂牛奶中的产量较低，且主要在稳定期检测到。当向牛奶中添加酪蛋白水解物时，肠球菌素产量更高且开始得更早，这表明额外的氮源对屎肠球菌在牛奶中生长的重要性。对于屎肠球菌RZS C5与切达干酪生产中使用的发酵剂的共培养，在牛奶发酵过程中未检测到肠球菌素活性。此外，在中试规模的切达干酪生产中测试了屎肠球菌RZS C5和屎肠球菌DPC 1146菌株的适用性。从奶酪生产开始就产生肠球菌素，并且在奶酪的整个成熟阶段都很稳定。这表明牛奶或奶酪的早期和晚期污染都可以通过稳定的原位肠球菌素产生来对抗。使用这种共培养是除良好生产规范之外的一项额外安全措施。
