Evaluation of Anaerobic Growth of Bacillus licheniformis and Bacillus subtilis in Tomato Juice

Conditions responsible for growth and pH elevation by selected strains of Bacillus subtilis and Bacillus licheniformis were studied in order to assess the potential hazard of metabiosis occurring between Clostridium botulinum and mesophilic Bacillus species in aseptically packaged tomato juice. The effects of the initial tomato juice pH on the growth of these Bacillus strains were evaluated. Cultures of B. licheniformis previously identified by Fields et al. (6) were reclassified as B. subtilis because none grew under strict anaerobic conditions nor used propionate. B. subtilis did not grow under strict anaerobic conditions but could use oxygen if present in the environment. None of the B. subtilis or B. licheniformis strains grew at pH 4.0 or 4.2. Only B. subtilis 075-T-09 and B. licheniformis 64-83-46 strains isolated from acidic foods were able to grow at pH 4.4 in tomato juice. Anaerobically, B. licheniformis strains did not grow in tomato juice or tomato juice with added nitrate and thiamine and even showed a loss of viability. Both B. licheniformis and B. subtilis require oxygen for growth in tomato juice at pH 4.4.