Chemicals Used to Control Microbial Growth: Study with Video Lessons, Practice Problems & Examples

Chemical agents for controlling microbial growth can be categorized into liquid and gaseous forms. Liquid agents include alcohols, aldehydes, halogens, and surfactants, while gaseous agents consist of ethylene oxide and formaldehyde. Their effectiveness is influenced by concentration, exposure time, temperature, and the presence of interfering chemicals. Understanding these factors is crucial for optimizing disinfection and sterilization processes, ensuring that microbial control is both effective and safe.

Chemicals Used to Control Microbial Growth

So when it comes to the chemicals that are used to control microbial growth, it turns out that there are many chemical agents that can be used for controlling microbial growth. And these chemicals can be grouped as being either liquid chemicals or gas chemicals. Now these chemicals that are used to control microbial growth are going to be able to kill microbes by irreversibly reacting with proteins, DNA, and the plasma membrane. And by interacting and reacting with those molecules, they can inactivate them and prevent them from doing their normal function. And so this is how chemicals can be used to control microbial growth. Now, below what we're showing you is a map of our lesson or our outline of the lesson moving forward in our course on the chemicals that are used for controlling microbial growth. And notice that our lesson is broken up into 2 parts, the left part over here and this right part over here. And so the left part is referring specifically to liquid chemicals. And the right part over here is specifically referring to gaseous chemicals or gas chemicals. Now moving forward in our course, we're going to be following the leftmost branches first. So we'll talk about the liquid chemicals first. And then after we talk about the liquid chemicals, we'll move on and talk about the gas chemicals at the end. And so the liquid chemicals as you can see here in our map include alcohols, aldehydes, biguanides, halogens such as chlorine and iodine, surfactants such as soaps, detergents, and quats, as well as heavy metals, phenolics, and peroxygens. And we will cover each of these liquid chemicals in more detail moving forward in our course by, again, following these branches from left to right. And then the gaseous chemicals that we're going to talk about moving forward include ethylene oxide, formaldehyde, and ozone. And so this here concludes our brief introduction to the chemicals that are used to control microbial growth. And once again, moving forward in our course, we'll get to talk a lot more about each of these different chemicals that are shown. So I'll see you all in our next video.

Which of the following chemical agents is a gas? 

• A. Quats.
• B. Alcohols.
• C. Ozone.
• D. Chlorine.

Factors Affecting Chemical Agents

In this video, we're going to talk about some factors affecting chemical agents that are used for controlling microbial growth. It turns out that the effectiveness of these chemical agents actually depends on multiple factors. Below we have a table listing some of these factors affecting these chemical agents. The first factor listed here is the concentration of the chemical agent being used. Some chemicals are effective when they are diluted. Diluting these chemical agents can be an important thing to do before using these chemical agents. Also, some chemical agents are going to be extremely toxic at high concentrations, which means that using diluted chemical agents can also be favorable. The actual concentration of the chemical agent can differentiate a disinfecting procedure versus a sterilization procedure.

Another important factor that affects the chemical agents is the exposure time, which is really just how long the microbes are exposed to the chemical agent, whether they are exposed for a short period or a long period. Some chemicals require really long exposure times and are less but still effective at shorter times. The exact exposure time will be an important factor to consider because it can greatly affect these chemical agents.

The third factor we have listed here is the temperature. Some chemicals have an optimal temperature at which they work best. If the temperature is too cold or too hot, it may prevent these chemical agents from being effective. The temperature is an important factor affecting these chemical agents.

The last factor we have here is the interfering chemicals because sometimes these chemical agents will react with other chemicals. Some chemicals may not be compatible with each other because they may react with each other. When they react with each other, they may inactivate one another, which means that these chemical agents can be affected by these other interfering chemicals. This is something that needs to be taken into account when a scientist is trying to determine the effectiveness of the chemical agent.

This concludes our brief lesson on some of the factors affecting these chemical agents that are used for controlling microbial growth. We'll be able to get some practice applying these concepts as we move forward in our course. So, I'll see you all in our next video.

Here’s what students ask on this topic:

What are the main types of chemicals used to control microbial growth?

The main types of chemicals used to control microbial growth can be categorized into liquid and gaseous forms. Liquid chemicals include alcohols, aldehydes, biguanides, halogens (such as chlorine and iodine), surfactants (such as soaps, detergents, and quats), heavy metals, phenolics, and peroxygens. Gaseous chemicals include ethylene oxide, formaldehyde, and ozone. These chemicals work by irreversibly reacting with proteins, DNA, and the plasma membrane of microbes, thereby inactivating them and preventing their normal function. Understanding these categories helps in selecting the appropriate chemical for specific microbial control needs.

How do concentration and exposure time affect the effectiveness of chemical agents in controlling microbial growth?

The concentration of a chemical agent is crucial as some chemicals are effective when diluted, while others are toxic at high concentrations. The concentration can also differentiate between disinfection and sterilization procedures. Exposure time, or the duration for which microbes are exposed to the chemical agent, is another critical factor. Some chemicals require long exposure times to be effective, while others can work in shorter periods. Both concentration and exposure time must be optimized to ensure the chemical agent effectively controls microbial growth without causing harm or being inefficient.

What are the factors affecting the effectiveness of chemical agents used for microbial control?

The effectiveness of chemical agents used for microbial control is influenced by several factors: 1) Concentration: Some chemicals are effective when diluted, while others are toxic at high concentrations. 2) Exposure Time: The duration for which microbes are exposed to the chemical agent affects its efficacy. 3) Temperature: Chemicals have an optimal temperature range where they work best; too hot or too cold temperatures can reduce their effectiveness. 4) Interfering Chemicals: Some chemicals may react with others, inactivating each other and reducing their effectiveness. Understanding these factors is essential for optimizing microbial control processes.

What are the differences between liquid and gaseous chemical agents used for microbial control?

Liquid chemical agents include alcohols, aldehydes, biguanides, halogens (chlorine and iodine), surfactants (soaps, detergents, and quats), heavy metals, phenolics, and peroxygens. These agents are typically applied directly to surfaces or used in solutions. Gaseous chemical agents, such as ethylene oxide, formaldehyde, and ozone, are used in their gaseous state and are often employed for sterilizing equipment and spaces where liquid application is impractical. The choice between liquid and gaseous agents depends on the application context, the type of microbes targeted, and the specific requirements of the disinfection or sterilization process.

Why is it important to consider interfering chemicals when using chemical agents for microbial control?

Interfering chemicals can react with the chemical agents used for microbial control, potentially inactivating them and reducing their effectiveness. This interaction can occur when multiple chemicals are used simultaneously or when residues of other chemicals are present. For example, certain surfactants may react with disinfectants, rendering them less effective. Therefore, it is crucial to consider the presence of interfering chemicals to ensure that the chosen chemical agent can function optimally and achieve the desired level of microbial control without unintended interactions.