BACTERIOPHAGE: Biological Aspects

CAPRA, M. L.; QUIBERON, A.; REINHEIMER, J. A.; GUGLIELMOTTI, D. M.

Reference Module in Food Sciences

Academic Press

Año: 2018; p. 1 - 9

Hugh Whitehead and Geoffrey Cox in 1935 identified the first bacteriophage (phage) specific for a lactic acid bacterium (LAB) at the New Zealand Dairy Research Institute. They discovered lactococcal bacteriophage as the causal agent of the complete breakdown of acid production experienced when using single-strain starters. Since then, phages infecting every species of LAB used in the dairy industry have been isolated. The phage infecting dairy lactobacilli was first isolated from sewage water in New York City. Later many Lactobacillus phages infecting strains of Lactobacillus delbrueckii (subsp. bulgaricus and subsp. lactis), Lactobacillus helveticus, Lactobacillus plantarum, and Lactobacillus casei/paracasei, among others, were isolated from traditional yogurt and other fermented foods. Likewise, the streptococcus thermophilus phages were first isolated almost 60 years ago in Switzerland. As Lactococcus lactis and S. thermophilus are responsible for most industrial dairy fermentations, the knowledge focusing on phages infecting these species is more extensive and deeper. Less information regarding phages attacking heterofermentative BAL of dairy importance could be found, such as those from Leuconostoc genera. Leuconostoc are generally present in mixed starter cultures together with homofermentative La. lactis. While the latter are responsible for producing great amounts of lactic acid, the former produces flavor compounds (principally diacetyl) and CO2. Diacetyl is an important flavor compound in semihard Dutch-type cheeses (e.g. Gouda), and CO2 is important for eye formation and the texture of semi-hard cheeses and for the opening of the matrix of molded cheeses. Since Leuconostoc strains do not contribute significantly to lactic acid production in milk, phage infections of Leuconostoc cultures may remain unnoticed during processing but will negatively impact on final fermented products. Since the discovery by Whitehead and Cox, phages of LAB have been the subject of ongoing research to understand the interaction between them and bacteria, and to exploit this knowledge for the improvement of valuable LAB strains. However, the inhibitory effect of bacteriophage against lactic acid starters is still recognized as one of the major and persistent troubles in dairy fermentation processes.