Question

1. We discussed phage in the context of sausage fermentation; it is also a serious concern in many modern, high-throughput cheese fermentations. However, phage problems never occur during traditional sauerkraut or kefir fermentations. Why would this be the case?

2. Is phage likely to be a problem in beer fermentations? Why or why not?

Answer 1

• Sauerkraut is fermented cabbage consumed as a salad/side dish in western countries and has an acidic and sour taste. The process of fermentation is carried out by removing the outer leaves, shredding the cabbage, and mixing it with salt and then kept in tanks covered to allow fermentation to take place for certain days or weeks. The presence of live bacteria Leuc. mesenteroides and Lb. plantarum act as a source of probiotics for Sauerkraut restricting the growth of phage during the fermentation process. The addition of salt also limits the growth of phage. Kefir is a traditional buttermilk that is viscous, acidic, slightly effervescent, and alcoholic in nature produced by the fermentation of milk with kefir grains. Kefir grains contain Lactic acid bacteria, acetic acid bacteria, and yeast which therefore makes kefir a high source of probiotic and hence limits the growth of phage. The conversion of carbohydrates like starch and sugar by the probiotics into alcohol and or acids which act as a natural preservative, prevents the growth of phage.
• Lactobacillus Brevis, Lactobacillus lindneri and Pediococcus damnosus, and some Gram-negative bacteria such as Pectinatus cerevisiiphilus, Pectinatus frisingensis, and Megasphaera cerevisiae cause beer spoilage by turbidity, acidity and producing unpleasant smell like that of hydrogen sulfide. Studies have indicated that lytic bacteriophages have proved useful in destroying the beer spoiling bacteria by infecting and lysing the bacterial cell wall, disrupting the bacterial metabolism, and finally causing cell death. Bacteriophages are natural and an inexpensive way of preventing the beer spoilage and thus act as a novel regimen for the destruction of bacteria spoiling the beer.