食品安全监管食品安全 (8).pdf

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1、Science-based Food Safety Supervision(SFSS)by Dr.S.Z.Tang Biofilm and Food Safety Hazards during post-processing Science-based Food Safety Supervision(SFSS)by Dr.S.Z.Tang 2 What is biofilm?A community of microorganisms attached to a surface.It is look like a film but there are live microorganism ins

2、ide.Contrast to“planktonic”cells:Individual cells suspended in a fluid medium(http:/www.personal.psu.edu/faculty/j/e/jel5/biofilms/)Biofilm formation in the water bed Science-based Food Safety Supervision(SFSS)by Dr.S.Z.Tang 3 How is the biofilm formed?http:/www.personal.psu.edu/faculty/j/e/jel5/bio

3、films/Science-based Food Safety Supervision(SFSS)by Dr.S.Z.Tang How is the biofilm formed?Science-based Food Safety Supervision(SFSS)by Dr.S.Z.Tang Figure from:Kolter,R.and R.Losick.1998.One for all and all for one.Science 280:226-227.How is the biofilm formed?Science-based Food Safety Supervision(S

4、FSS)by Dr.S.Z.Tang Three key processes of biofilm formation Attachment Adsorption/adhesion of a microbial cell to a solid surface.Colonization Establishment of a microbial community at the site of attachment.Growth Maturation of a three-dimensional biofilm community.Science-based Food Safety Supervi

5、sion(SFSS)by Dr.S.Z.Tang Why can bacteria biofilm be formed?For resistance to extreme conditions Heat&cold Starvation Dessication Resistance to toxic substances For survive and long life Science-based Food Safety Supervision(SFSS)by Dr.S.Z.Tang Function of Biofilm Science-based Food Safety Supervisi

6、on(SFSS)by Dr.S.Z.Tang What is the biofilm more resistant?Special structure Very thick and stick outside layer Polymers Science-based Food Safety Supervision(SFSS)by Dr.S.Z.Tang What is the biofilm more resistant?Special quorum sensing(QS)?The sensing of population density.QS is a unique characteris

7、tics of biofilm.Quorum sensing provides communication among bacteria via molecules released into the environment.The concentration of released molecules reflect population density.QS regulates gene expression including virulence gene expression.Science-based Food Safety Supervision(SFSS)by Dr.S.Z.Ta

8、ng What bacteria can form biofilm?Staphylococcus aureus Staphylococcus mutans Salmonella typhi Enterococcus faecalis Pseudomonas aeruginosa Listeria monocytegenes Cronobacter sakazakii Science-based Food Safety Supervision(SFSS)by Dr.S.Z.Tang Listeria monocytogenes biolfilm formation at different da

9、ys Photo at 6 h,2 d and 7 d.Science-based Food Safety Supervision(SFSS)by Dr.S.Z.Tang Listeria monocytogenes biolfilm formation at different temperatures Photo at 4,12,22,and 37 Science-based Food Safety Supervision(SFSS)by Dr.S.Z.Tang Autoinducers Small molecules released into environment for quoru

10、m sensing are called autoinducers Gram-negative bacteria use AI-1 and AI-2 molecules as autoinducers.Gram-positive bacteria use processed oligopeptides for communication.(Miller and Bassler.2001)Science-based Food Safety Supervision(SFSS)by Dr.S.Z.Tang Disruption of Biofilm Objectives BIOFILM-PLANKT

11、ONIC Disrupt the EPS matrix that binds cells together Promote cell detachment from the surface Much room for R&D Biofilm disrupting chemicals Methods of implementing/delivery Science-based Food Safety Supervision(SFSS)by Dr.S.Z.Tang Biofilm and Food safety Most pathogenic bacteria can form biofilm g

12、enerally ignored by industry.Safe food biologically in terms of traditional pathogenic bacteria as the form of planktolic may not be safe.Research should be done for the strategies of biofilm formed pathogens.Science-based Food Safety Supervision(SFSS)by Dr.S.Z.Tang Bacteria in biofilm still survive

13、 after antimicrobial treatment under confocal laser microscope Brochothrix thermosphacta biofilm treated with 0.5%trisodium phosphate&strained with fluorescent viability.Red-dead,green-live Science-based Food Safety Supervision(SFSS)by Dr.S.Z.Tang Disruption of Biofilm Prevent settlement alter surfa

14、ce properties inhibit cell-to-cell signaling Induce dispersal nitric oxide(NO)alter cell-to-cell signaling detergents physical removal Science-based Food Safety Supervision(SFSS)by Dr.S.Z.Tang Biofilm Book Pina M.Fratamico,Bassam A.Annous and Nereus W.Gunther IV.(2009).Biofilms in the food and beverage industries.NY:Woodhead Publishing Limited and CRC Press LLC.(TS205,pp580,Y1870)Science-based Food Safety Supervision(SFSS)by Dr.S.Z.Tang Questions What is biofilm?What is special for Biofilm?Why is biofilm formed pathogen ignored?What would be solutions for biofilm pathogen control?