Anti-biofilm forming and anti-quorum sensing activity of selected essential oils and their main components on food-related micro-organisms.

AIMS: The aim of this study was to investigate the effect of clary sage, juniper, lemon and marjoram essential oils (EOs) and their major components on the formation of bacterial and yeast biofilms and on the inhibition of AHL-mediated quorum sensing (QS). METHODS AND RESULTS: Biofilm formation was measured by crystal violet and resazurin staining, and QS inhibition was detected by paper disc diffusion assay. Marjoram EO inhibited Bacillus cereus, Pichia anomala, Pseudomonas putida and mixed-culture biofilm formation of Ps. putida and Escherichia coli and showed the best QS inhibitor effect on Chromobacterium violaceum. For B. cereus, all components showed better antibiofilm capacity than the parent EOs. Lemon EO inhibited E. coli and mixed-culture biofilms, and cinnamon was effective against the mixed forms. Scanning electron microscopy showed the loss of three-dimensional structures of biofilms. CONCLUSIONS: The EOs and components used seem to be good candidates for prevention of biofilm formation and inhibition of the AHL-mediated QS mechanism. SIGNIFICANCE AND IMPACT OF THE STUDY: Biofilm formation on foods and food industrial equipment is a serious problem causing food spoilage and emergence of foodborne diseases. This article highlights the importance of studying EOs as potential disinfectants and food preservatives.

Continuous production of ethanol using yeast cells immobilized in preformed cellulose beads.

Saccharomyces cerevisiae cells were immobilized on preformed cellulose beads by adsorption. The fermentation capacity of the immobilized yeast cells was found to be practically independent of the hydrogen ion concentration between pH 3.1 and 6.25. The fermentation capacity was maximal at 30 degrees C. The immobilized yeast cells were used for continuous production of ethanol in a fluidized-bead reactor. The average values characteristic for the process were an ethanol concentration of 41.9 +/- 0.1 g1(-1), a fermentation efficiency of 82.9 +/- 2.1% and a volumetric productivity of 3.94 +/- 0.52 g1(-1) h-1.