SOME INVESTIGATIONS ONLACTOBACILLUSINFECTION

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Abstract
Studies on the comparative growth rates of a strain of a typical beer Lactobacillus in beer, beer extract, hopped and unhopped wort, showed that, in beer extract, the growth is more prolific than in the other media. Factors necessary for optimal growth in beer extract were studied, the effects of pH, temperature, concentrations of yeast extract and maltose, and oxygen tension being determined. Using the medium so developed, the concentrations of some sterilizing agents, required to kill lactobacilli in brewery equipment, were found to be: cetyltrimethylammonium bromide, I: 5,000; formaldehyde, 2%; caustic soda, 1%; sodium hypochlorite, 0.1% available chlorine; hot water at 66–71deg; C. was also lethal. With acid phosphate buffer, a pH of 1.5 is necessary to kill these organisms within 2 hr. at 10–13deg; C. The optimal temperature for growth in bulk beer is found to be approximately 30deg; C., and the critical pH which prevents development is 3.7-3.8, according to the beer. A test for detecting lactobacilli in water, wort, brewery yeast, and beer is described, and experience with different techniques for preserving these organisms is discussed. Using sensitive methods, strains of beer lactobacilli have been isolated from malt and air.