ACETOBACTER SPECIES CAPABLE OF INFECTING BEER

Hitherto, the only representatives of the genus Acetobacter which have been separated in pure culture from beers in this country, and concerning which adequate descriptions have been published, are A. viscosum Baker, Day, and Hulton, A. capsulatum Shimwell, and A. turbidans Cosbie, Tošić, and Walker. The object of the present work was to gain an estimate of the respective abilities of other known species of Acetobacter to act as infections in top fermentation beer, this information being required as an aid to the identification of Acetobacter species which the authors have isolated recently from beers and from pitching yeasts. The behaviour of authentic cultures of ten well‐known species of Acetobacter ( A. capsulatum was included for purposes of comparison) when introduced into sterile samples of various beers under suitable conditions for growth has been observed. A. acetigenum, A. acetosum and A. capsulatum were most active in causing deterioration of the beers. Next to these in order of rate of development came A. ascendens , whilst A. aceti and A. pasteurianum showed themselves to be relatively slow growers under the conditions of these tests. The two last‐named organisms are sufficiently active, nevertheless, to be regarded as objectionable beer disease bacteria. A. gluconicum, A. kützingianum, A. suboxydans , and A. xylinum gave no evidence of growth in beer during an incubation period of 28 days. Since A. kützingianum and A. suboxydans were isolated originally from Continental beers their failure to develop in the present case may be a result of previous long continued cultivation in an artificial environment.