We have generated a recombinant strain of B. thuringiensis that co-synthesizes two bacteriocins (kenyacin 404, thurincin H) with improved inhibitory activity, when compared with parental strains. To our knowledge, this is the first study that shows that B. thuringiensis could be manipulated to produce two bacteriocins, one being of heterologous origin, that enhance the antibacterial activity of the recombinant strain.

The British Standard protocol currently used to determine the nisin concentration in cheese requires the manipulation of a 40 g sample involves two critical points, pH adjustment and heating/cooling. In this work, we developed a fast micromethod that permits the manipulation of 0.2 g cheese, substitutes the use of 0.02N HCl by 50 mM citric acid and facilitates the handling of many samples in reduced time, and with increased efficiency/yield. This change keeps the pH stable at ~3.4, enough to sidestep the pH adjustment, and nisin antimicrobial activity was stable at boiling temperatures.