Aims: To study Bacillus contamination of wheat flour and ropy bread, to analyse genetic diversity of isolated strains and to evaluate the ability of these strains to produce ropy bread.
Methods and results: Classical and molecular methods [16S rDNA sequencing and random amplified polymorphic DNA (RAPD)-PCR] were used to identify and type-isolated strains. The predominant species isolated were Bacillus subtilis and B. licheniformis. RAPD analysis demonstrated that the same sample may harbor different strains. Ten of 15 strains of B. subtilis and four of six strains of B. licheniformis were able to cause rope spoilage of the laboratory-baked bread.
Conclusion: RAPD typing can be useful in the tracking of Bacillus strains during bakery processing and in the understanding of the role of different Bacillus strains in the rope spoilage of bread.
Significance and impact of the study: The results indicate the variability of Bacillus strains isolated from flour and responsible for rope spoilage of bread.