The heat resistance of spores from biofilms of Bacillus cereus grown in tryptic soy broth and milk

Bacillus cereus is a concern for the dairy industry due to the biofllm and spore formation during the manufacture of dairy products, causing contamination in the final products. Biofllm spores of all tested isolates showed a significantly higher (P < 0.05) or statistically comparable D-90 degrees value than their planktonic spores. The dipicolinic acid (DPA) content was measured and suggested not responsible for the differences in D-90 degrees values observed. The intracellular structure of spores was observed under transmission electron microscopy, showing a clearly defined circular coat for biofllm spores while an irregular-shaped coat was observed for planktonic spores. This is the first manuscript considering factors including biofllm formation, DPA content and spore structure in milk. This suggests more severe heat treatments are needed to control B. cereus spores from biofilms in the dairy industry compared with spores from planktonic cultures without the presence of milk. (C) 2021 Elsevier Ltd. All rights reserved.