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1. Evaluate if production in broth can be achieved by adding crude lantibiotic to increase signal transduction. </P>
2. Evaluate a classical mutagenesis approach to optimize lantibiotic production. </P>
3. Determine the range of the antimicrobial activity of this lantibiotic. </P>
4. Produce a de-lactose whey fermentate powder using this culture.
The objective of this exploratory project was to develop a whey-based fermentate that contains probiotic lantibiotic-producing bifidobacteria. The fermentate would be spray dried into a powder and used as a food ingredient to protect against prominent food pathogens such as E. coli and Salmonella. A lantibiotic is a modified protein with broad-spectrum antimicrobial activities. The only commercially available products that have broad-spectrum antimicrobial activities are those that inhibit gram-positive bacteria, not gram-negative bacteria such as E. coli and Salmonella. Researchers previously discovered a probiotic bifidobacterium called Bifidobacterium longum subsp. longum (DJO10A) that produces this lantibiotic compound, but only on solid media (agar), not in liquid medium. </P>The results of this study show that the lantibiotic gene cluster could be switched on in broth in a dose dependant fashion, up to the maximum level of added inducer of 160 AU. To maintain expression of the gene cluster, the culture could be sub-inoculated at a minimum of 10% to maintain sufficient levels of the induced in the medium. Researchers were unable to detect the lantibiotic compound in the supernatant, but detected a 3.2 kDa lantibiotic peptide in the pellet using Maldi-Tof MS. The obtained mutants and grew them in the presence of 250 AU/ml of a crude lantibiotic preparation. Researchers determined that none of the mutants significantly increased lantibiotic production. An antimicrobial spectrum analysis of this crude lantibiotic preparation revealed a broad spectrum of both gram-positive and gram- negative bacteria, illustrating its potential usefulness as a natural food preservative. This exploratory project demonstrated that the broad-spectrum lantibiotic of B. longum DJO10A could be produced in broth cultures. In order to achieve a whey-based fermentate with the lantibiotic-producing B. longum DJO10A, more research is needed to optimize production the lantibiotic in broth cultures.