Ryan M P, Ross R P, Hill C
Dairy Products Research Centre, Fermoy, County Cork, Ireland.
Appl Environ Microbiol. 2001 Jun;67(6):2699-704. doi: 10.1128/AEM.67.6.2699-2704.2001.
The aim of the present study was to develop adjunct strains which can grow in the presence of bacteriocin produced by lacticin 3147-producing starters in fermented products such as cheese. A Lactobacillus paracasei subsp. paracasei strain (DPC5336) was isolated from a well-flavored, commercial cheddar cheese and exposed to increasing concentrations (up to 4,100 arbitrary units [AU]/ml) of lantibiotic lacticin 3147. This approach generated a stable, more-resistant variant of the isolate (DPC5337), which was 32 times less sensitive to lacticin 3147 than DPC5336. The performance of DPC5336 was compared to that of DPC5337 as adjunct cultures in two separate trials using either Lactococcus lactis DPC3147 (a natural producer) or L. lactis DPC4275 (a lacticin 3147-producing transconjugant) as the starter. These lacticin 3147-producing starters were previously shown to control adventitious nonstarter lactic acid bacteria in cheddar cheese. Lacticin 3147 was produced and remained stable during ripening, with levels of either 1,280 or 640 AU/g detected after 6 months of ripening. The more-resistant adjunct culture survived and grew in the presence of the bacteriocin in each trial, reaching levels of 10(7) CFU/g during ripening, in contrast to the sensitive strain, which was present at levels 100- to 1,000-fold lower. Furthermore, randomly amplified polymorphic DNA-PCR was employed to demonstrate that the resistant adjunct strain comprised the dominant microflora in the test cheeses during ripening.
本研究的目的是开发辅助菌株，使其能够在奶酪等发酵产品中，在由产生乳酸链球菌素3147的发酵剂所产生的细菌素存在的情况下生长。从一种风味良好的市售切达干酪中分离出一株副干酪乳杆菌副干酪亚种菌株（DPC5336），并将其暴露于浓度不断增加（高达4100任意单位[AU]/毫升）的羊毛硫抗生素乳酸链球菌素3147中。这种方法产生了该分离株的一个稳定的、抗性更强的变体（DPC5337），它对乳酸链球菌素3147的敏感性比DPC5336低32倍。在两项独立试验中，将DPC5336与DPC5337作为辅助培养物进行比较，分别使用乳酸乳球菌DPC3147（天然生产者）或乳酸乳球菌DPC4275（产生乳酸链球菌素3147的转接合子）作为发酵剂。这些产生乳酸链球菌素3147的发酵剂先前已被证明可控制切达干酪中偶然出现的非发酵剂乳酸菌。在成熟过程中产生了乳酸链球菌素3147并保持稳定，成熟6个月后检测到的水平为1280或640 AU/克。在每次试验中，抗性更强的辅助培养物在细菌素存在的情况下存活并生长，在成熟过程中达到10⁷ CFU/克的水平，相比之下，敏感菌株的水平要低100到1000倍。此外，采用随机扩增多态性DNA-PCR来证明抗性辅助菌株在成熟过程中是试验奶酪中的主要微生物群落。
