Chapter 8 Biofilm and Food Safety by Dr. Tang在线视频

Chapter 8 Biofilm by Tang

Hello, Ladies and Gentlemen, welcome to our course, scientific food safety supervision. In today’s lecture, I would like to talk a new topic which is called biofilm, related to our food safety

Biofilm is a hazard during the post-possessing. So what is biofilm? Biofilm actually is a community of microorganisms, attached to the surface, so it means in the film it is not only some kind of substances inside, also there are live bacteria or microorganism inside, it looks like a film, but inside, there is microorganism inside. This slide shows you the biofilm, what it looks like as a biofilm.

This slide shows you the stages of development for biofilm formation. This slide is clearer for the four stages of the biofilm formation. And this shows the biofilm cycle, and the cycle of these three stages or four stages. The first stage is attachment, it means planktonic or free bacteria first of all attach to the surface of the equipment or the facilities in the food industry. And then they release some kind of stick substances, which actually is carbohydrate, look like gel, and then glue it, and then finally they release. So this is a cycle.

So why can bacteria biofilm be formed? This bacteria biofilm is formed for their own survival and for their long life because they want to survive longer in the extreme environment, for example, the very hot weather and cold weather, or antibiotic environment or desiccation.

So what is the function for biofilm? That means what they are doing here? As I said, they just want to response to the stress, extreme environment. These four photos show four different kinds of stress to the biofilm. This again shows you the different part of, different stages of the stress for the biofilm. So why the, again, the bacteria biofilm be formed and for survival and also they have special reason for that. So what is the special for the biofilm, for this kind of biofilm? There are two main reasons. The first one is that they have very special structures, you see, the film outside the membrane is very thick. So it’s not easy for antibiotics or some other factors to enter to these bacteria.

The second reason is that there is not only one single bacteria inside, actually it’s a community of the bacteria inside, so they come together in the same environment, or in the room, when they contact each other, they have some kind of signals to communicate each other. This is called quorum sensing. Because of the quorum sensing, they would give new gene expression. And also they have new expression, new performance, and these performance come together, they resistance to different environment. And make them more difficult to be removed, to be killed. So what bacteria can be biofilm formed actually is based on the research data? About 80% of bacteria can form biofilm, of course, not many researchers have done on this.

Here is an example of bacteria easily biofilm formed, for example, Cronobacter and Listeria and Staphylococcus, those are the typical one, easily to be formed for the biofilm.

And this slide shows the differences of the Listeria monocytogenes biofilm compared to the planktonic bacteria during different days. At different days, they are formed in the different stages. For example the first one, the first photo, is just the planktonic one. The second one they are getting together. The third one is real film. It is differently. And this slide shows Listeria monocytogenes at different temperature. You see the first one is 4°C, that means cold temperature. You see the final one, is 37°C, it is a little bit warm temperature. So the warm temperature is easily to get biofilm. And then this one come together, based on the research they have some factors to induce this biofilm formation, which is called auto-induced, also here show the chemical structure, it’s auto inducers.

So this is the factor for biofilm, so how to prevent this kind of biofilm? How to prevent, how to control this biofilm? So our objective is to interfere the pathogenic one, we want to control it, we want to remove it. And based on the mechanism of this biofilm formation. There are three to four stages altogether. The first stage is attaching it from the planktonic one, from planktonic one to the biofilm, that is a natural process of biofilm formation. Now how to control it? We do another way. So can we do it from the biofilm to the planktonic one? Then we stop it or we control it, or we inhibit it, inhibit the process from the planktonic to the biofilm. So of course, this is the new topic, we need do more research on that, so this slide shows you the relationship between biofilm and the food safety issue.

So this is the result under the electro-microscope, you see the pigments, the red one, the different light inside, so the, someone is dead, someone is alive, so generally we think, after the antimicrobial treatment, all those bacteria should be dead, and should be in one color. However, when we show this one, a lot of them are different colors, you see a lot of bacteria are still alive, indicating the biofilm is more resistant to the environment, but we thought it is already be killed. So this is the potential risk for our food and food industry, food products. So for the biofilm and in the food industry, this is the new topic as research come in. We have the book to refer. In this book, we will learn how the biofilm is formed, what the mechanism is, and what the huge area for us to do is.

So in today’s lecture, I have just talked about the new topic of food safety which is called biofilm. Now I have questions for you to think?

First, what is biofilm? Second, what are the special characteristics or special features for this kind of biofilm? And the third question is, why is this biofilm formed? What is, in particular, for the pathogenic bacteria? And then the final one, what should be the solution or the strategies to control this kind of pathogenic biofilm?

This is end of this lecture today. Thank you so much. See you next time.