When considering the cleaning and sterilization of microbes in factories, it's crucial to understand the concept of biofilms. This article simply and clearly explains what biofilms are, their formation process and mechanism, the physiological characteristics of biofilm cells, the areas in food factories where they are likely to form, and methods of removal.
What are Biofilms?
Imagine waking up in the morning and feeling the slimy stuff on your teeth – that's a biofilm. Or think of the stubborn plaque at the base of your teeth; it’s akin to a tough biofilm that’s taken root somewhere in a factory line.
Despite cleaning and maintaining hygiene in food manufacturing plants, there are often cases where products get mysteriously contaminated by microbes. This could be due to biofilms formed somewhere along the production line.
Biofilms are Resistant to Medication
Let’s look at the growth curve of microbes. When microbes actively multiply and increase their numbers in a test tube, it’s called the logarithmic growth phase. Eventually, nutrients deplete, and microbes can't multiply further – this is the stationary phase. Left as is, the microbes will gradually die, known as the death phase.
Now, if we stress microbial cells, which stage would be strongest? The weakest would be the death phase, of course. But between the logarithmic growth and stationary phases, which is more resistant to stress? Many would think cells in the logarithmic growth phase are stronger, likening them to humans in their teens and twenties. However, in microbes, cells in the stationary phase show stronger resistance to stress.
Microbes are more resistant to various stresses in the stationary phase, where growth has slowed, than in the active logarithmic growth phase. Let’s explain this with an easy analogy.
The Battle of Okehazama in 16th century Japan saw the minor lord Oda Nobunaga face the powerful Imagawa Yoshimoto. Imagawa, with a force more than ten times larger than Nobunaga's, was confident of a quick victory. However, Nobunaga, despite being outnumbered, launched a surprise attack and defeated Imagawa. This battle showed that a smaller, well-strategized force could win, elevating Nobunaga’s fame and paving his way to unify Japan. Imagawa's downfall at Okehazama can be likened to the logarithmic growth phase of microbes – overconfident and unprepared.
Conversely, even a minor lord can put up a strong defense when barricaded in a castle, as seen in 16th century Japan. Ishida Mitsunari, a general under Toyotomi Hideyoshi, faced fierce resistance trying to capture a small castle despite outnumbering its defenders 20 to 1. This example mirrors microbes in the stationary phase or biofilm state, demonstrating high resistance to attacks.
Thus, the principle of a fortified defense being difficult to overcome applies to both history and microbiology.
All organisms are better prepared for adversity if they've experienced some hardship. In this preparatory stage, cells produce stress proteins. These proteins are found not only in microbes but also in higher animals.
In factories, microbes proliferate when nutrients are abundant. However, factory environments are not nutrient-rich like food, so microbes adhere to surfaces and form biofilms. These biofilms make microbes more resistant to disinfectants. This resistance isn’t just because biofilms have layers of organic matter and cells impeding disinfectant penetration. Experiments show that biofilm cells, even when detached from surfaces and tested, are more resistant to disinfectants than those grown in test tubes. This indicates a fundamental change in the cell properties of biofilm-forming microbes, likely due to the aforementioned stress proteins.
Thus, understanding the concept of biofilms is essential in cleaning and sterilizing factories.
Where Biofilms are Likely to Form
Where do biofilms form?
In factory environments, high-risk areas include underneath large equipment where regular cleaning is missed.
Also, the insides and outsides of pipes, which are hard to clean,
and even the undersides of factory floor mats can harbor biofilms.
The wheels of trolleys used to transport goods in the factory can also be difficult to clean and may spread biofilm-derived microbes around.
Faucets are often overlooked; though sinks are easy to clean, the faucets themselves, touched by many hands, can easily develop biofilms.
Cleaning tools like sponges, brushes, and gloves,
as well as electrical control panels with buttons touched by many workers, can also be breeding grounds for biofilms.
Invisible scratches on stainless steel surfaces can accumulate organic matter, leading to biofilm formation.
Biofilm Removal Methods
There are no special methods for removing or sterilizing biofilms. As mentioned in another article, the key to microbial extermination in food factories lies in cleaning. It's vital to first identify areas where biofilms have formed, then physically remove them or use chemical cleaning to treat them as organic dirt. The nature of the organic matter coexisting with biofilms, like lipids or proteins, varies depending on the factory, so cleaning methods should be tailored accordingly. Trying to sterilize biofilms without cleaning is a mistake.
※For the basic concept of sterilization in food factories, please refer to the following article:
Food Factory - Sterilization and Cleaning: Which is More Important?
