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Microbiom Health & Wellbeing Care & Cosmetics
Reading Time 11 min
September 17, 2024

The surface of our body is home to a large number of microorganisms that are beneficial to our health. Cosmetics should not disturb the natural microbiome of the skin. For this reason, a team at Evonik led by microbiologist Stefan Pelzer has developed a model that can be used to test important ingredients

We can’t see them. We can’t hear them. We can’t feel them. But they are everywhere—our bodies are covered in them: microorganisms. These tiny organisms are invisible to the naked eye and colonize our skin in unimaginable numbers.

An estimated 30 trillion bacteria live in and on a human body. They cavort in the pores on our arms, multiply in the sebum of our nose or feed on the sweat from the moist warmth of our armpits.

Sounds gross? It is, in fact, completely natural. Humans are even dependent on these fellow inhabitants. For example, they keep the skin’s protective acid mantle stable and provide natural protection against pathogens. Without a stable skin microbiome, as the community of microbes on our skin is called, pathogens would have an easy time of it.

It is therefore worthwhile to look after the healthy microorganisms on the skin as well as the skin itself. But is that even possible, given the many cosmetics used in our bathrooms? According to surveys, half of all people in Germany use skin care products every day. Worldwide sales of cleansers and creams, lotions and masks, serums and oils will reach several hundred billion US dollars this year.

Three pipettes on a machine take samples from small glass sample containers.
Michelle Dargatz sits in front of a closed container into which she reaches with airtight gloves.
As some of the bacterial strains used cannot tolerate oxygen, biotechnologist Michelle Dargatz places them in a suitable oxygen-free culture medium

A diverse community

But what effect do these care products have on the skin microbiome? Do they unbalance it? And if so, how could this be prevented? Professor Stefan Pelzer and his team are investigating these questions in Halle-Künsebeck, not far from Bielefeld. The microbiologist has been with Evonik since 2012 and is the head of microbiome research at the company’s Biotech Hub. The company has high hopes for biologically based, biotechnologically produced, and biodegradable solutions. The Biotech Hub combines expertise in this field and has around 150 employees working on almost 80 projects at three different locations.

Pelzer, who has already promoted research into the gut microbiome for the Animal Nutrition unit, is currently working with his team on creating a basis for assessing the effect of cosmetics on the skin microbiome early on in the laboratory phase. Evonik also develops, produces, and markets ingredients for skin care products. Customers of the Care Solutions unit are cosmetics companies that want to translate the latest findings on the microbiome and the interest of potential end consumers into a corresponding product range.

This requires active ingredients and excipients that are demonstrably “microbiome-friendly.” Manufacturers use them to formulate products that can be advertised with the corresponding promise. “This is what we call a product that neither disrupts the reproduction of the microorganisms nor seriously alters their diversity,” explains Pelzer.

Stefan Pelzer leans on a high table. A laboratory room can be seen behind him.

The “natural population” includes, for example, staphylococci, which like to arrange themselves in grape-like formations; corynebacteria, which look like small clubs under the microscope; rod-shaped cutibacteria; and many more. The community of microorganisms is diverse, but differs in its composition depending on which part of the body you look at. The same bacteria do not live in the moist environment of the back of the knee as on the rather dry forearms. And in the sebum of an oily forehead, which is exposed to a lot of sunlight, different co-inhabitants feel at home than in intimate areas, where bacteria have to make do with little light and oxygen. Only very specific species can be found almost everywhere as “all-rounders”—and that’s why Evonik focuses on them.

Michelle Dargartz enters data from a display, holding a sample vial in her hand.

The term “microbiome” was coined in 2001 by the late US microbiologist and Nobel Prize winner Joshua Lederberg. The enthusiasm for this topic has been great ever since. Initially, the main focus was on the gut microbiome. There is no longer any doubt that the community of microbes in the digestive tract plays a key role in our health and well-being. It is even said to be linked to diseases such as diabetes or Alzheimer’s. “What we know about the inhabitants of the intestines of humans and animals is a great help when we’re researching the skin microbiome,” reports Pelzer. “For example, we can adopt technologies from gut microbiome research and learn a lot about the right approach.”

Portraitbild Stefan Pelzer

»Our model also captures the interactions and dependencies between the bacteria«

Prof. Dr. Stefan Pelzer Head of microbiome research at Evonik’s Biotech Hub

The microbes that live on a person’s skin are already determined at birth: If a baby is born by caesarean section, different bacteria colonize its skin than after a natural birth. Later, age, hormones, the immune system, antibiotic treatments, the place of residence, and lifestyle influence the ecosystem on the skin. How often do we expose ourselves to the sun? What climate do we live in? How often do we shower, what do we use to wash ourselves, and what creams do we apply afterwards.

Competitors on the skin

How cosmetics and their ingredients affect the skin has so far mostly been tested without adequate consideration of the microbiome. Tests were limited to a few bacterial species at best. “That’s too simplistic,” says Pelzer, who is concerned with creating realistic test conditions in the laboratory. After all, numerous microbes live together on the skin. They are in competition or benefit from each other. They communicate via messenger substances and influence each other’s growth. “We have therefore developed a microbiome model covering the most important skin microbes. For the first time, this model also captures the interactions and dependencies between the bacteria,” explains Pelzer, who is currently also President of the Association for General and Applied Microbiology (VAAM). “That’s because well-groomed skin, no matter where it is, depends on a balanced microbiome.”

Pelzer’s team does not view the microbes in isolation, but as a community. A microbiome model was developed based on the needs of the cosmetics industry and building on initial experiments at Creavis, Evonik’s strategic research unit. The researchers in Halle-Künsebeck took the different skin zones—dry, moist, oily—as a model and created co-cultures from those bacteria that colonize all three areas. In these co-cultures, eight to ten of the most common microbial species grow simultaneously in culture media, excrete metabolic products, and interact and compete with each other, just like on human skin. Exposing them collectively to the ingredients of cosmetics can influence their interaction. This means that the complexity of the system far exceeds that of the tests available to date.

Product launches 2004 (there were 2) to 2023 (there were 1660)
Newly launched cosmetic products that target the microbiome Source: Mintel Group Ltd.

You can’t see with the naked eye how microbes react to surfactants, ceramides, oils or moisturizing substances. However, the breakdown of the specific bacterial DNA in a sample reveals exactly which microbes tolerate a test substance well and which may disappear completely. “We have found that some ingredients hardly influence diversity and growth,” reports Pelzer. “Other substances that are available on the market had huge effects on the diversity of skin bacteria.”

Preservatives are something of a challenge for the creation of a microbiome-friendly product. They are essential to ensure that a cream in a jar keeps after opening. After application, however, they also inhibit the growth of “good” bacteria on the skin, at least temporarily. The aim here is to find agents that fulfill their function as preservatives on the one hand and do as little harm as possible to the microbiome on the other.

At the Hamburg location, a team from Care Solutions is working on precisely this task. It is developing preservatives exclusively from natural raw materials.

If the bacterial community on the skin is out of balance for a longer period of time, for example due to antibiotics or excessive hygiene, this weakens the skin’s barrier function. Undesirable microorganisms can then gain the upper hand. Here’s one example: Cutibacterium acnes is one of the most common representatives on human skin. However, if certain strains become too dominant, this can promote acne. It can also cause a yeast to spread more easily, causing dandruff to form. In addition to cosmetics that disturb the microbiome as little as possible, Evonik’s research is also looking at care products that actually promote the growth of certain bacteria—similar to how probiotic yogurts can be used to keep the intestinal flora healthy.

Samples with test liquid are panned in an analyzer.

Freezer and incubator

Many of the tests are carried out in the laboratory in Halle-Künsebeck under strict safety regulations. Access is only permitted after individuals receive a briefing and don a smock and safety goggles. On the one hand, these rules protect the valuable cultures from contamination. On the other, they protect employees or visitors from the bacteria. The microbes are stored at minus 80 degrees Celsius in a freezer that is secured by a combination lock. More pleasant temperatures prevail in large incubators, which heat and swivel numerous glass flasks simultaneously. In a “hypoxic” station, scientists work with anaerobic microbes that can survive without oxygen. In a high-throughput cultivator and a microbioreactor, they multiply bacteria in a controlled manner and track their growth online. The researchers also use flow cytometry, a process in which cells can be distinguished from one another using laser light, to determine how well or how poorly the cultures are thriving.

Some of the work that people used to perform is now done by machines in the Evonik laboratory. In one room, high-tech robots pick bacteria from culture media; in another, they pipette and dilute samples via precise movements. “The automation of work steps saves us a lot of time,” says Pelzer. “It allows us to achieve results faster and creates capacity for other tasks.”

An example of this is the research into the microbiome in acne, which, at Evonik, is the responsibility of Michelle Dargatz. A biotechnologist, Dargatz has been working at the company for seven years and recently presented one of Evonik’s models at an international skin microbiome congress in The Hague. In Künsebeck, she is currently developing the first model to simulate problematic skin.

Evonik employee Michelle Dargatz prepares a sample in a multi-stage process in Halle-Künsebeck.

One of the reasons why people suffer from acne is that certain strains of Cutibacterium acnes feel particularly at home on their skin. They multiply excessively in the sebum and thus displace other microbes. Dargatz is investigating how bacterial communities, which are typically found on acne skin, react to certain ingredients in cosmetics. What is the effect of salicylic acid, for example, which is found in skin care products for blemished skin? How does Cutibacterium acnes react to anti-inflammatory zinc? And which substances improve the drainage of sebum without disturbing the “good” skin bacteria?

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FROM THE TEST TUBE TO THE SKIN

The first test with stress factors is currently under way in a laboratory sterile bank: Michelle Dargatz wants to test how her bacteria react to UV light, i.e. sunlight. They stand in bright blue light for a few hours, after which they are counted to see if they can still multiply normally.

“With the help of the two models for normal and acne-prone skin, we want to precisely understand microorganisms and their interactions in order to improve the products for our customers,” says Pelzer.

So far, the team has tested around 30 substances from cosmetics on the cultures, including both its own ingredients and products from customers. One important finding is that the formulation, i.e. the mix of different substances, can cancel out or change the effect of individual ingredients.

In the future, Pelzer’s team plans to use the skin microbiome models primarily to test ingredients and formulations from the Evonik laboratories. In addition, further microbiome models are to be developed that mimic scalps with dandruff, atopic dermatitis or older skin. Pelzer adds that computer simulations could soon support his research thanks to artificial intelligence and make predictions about the effects of substances.

A yellow liquid in around 30 small test tubes. At the bottom is sebum, an icy layer of fat.

The team at the Biotech Hub still examines the bacteria in test tubes, but Pelzer is already planning the next step. “In the future, the ultimate feat would be to study the microbes on artificial 3D skin tissue in order to also investigate their interaction with skin cells,” he says.

To achieve this goal, the group in Halle-Künsebeck works closely with other Evonik research units. Among them is the Evonik Skin Institute in Singapore, which was founded in March 2024. “Investigating how cosmetics affect the skin and what consumers can expect from the products is one of our specialties,” says the institute’s head, Dr. Jennifer Bourland, a cell biologist.

Her team not only works on cell cultures and tissues but also has tests carried out on volunteers. The Skin Institute thus serves as an interface between the market and science. For the past three or four years, the microbiome have been playing an increasingly important role in the cosmetics industry, reports Bourland. “And it’s now more than just a trend,” she says. “The skin microbiome has become a very important factor in the marketing of cosmetic products.”

More than 20 employees work with Bourland at the Skin Institute on various projects, but the biotechnologist is particularly fascinated by the microbiome. “It is becoming increasingly clear that it is not only associated with diseases but also interacts with the skin in healthy people and, like the gut microbiome, has an influence on many areas of our lives.”

Portrait Jennifer Bourland

Globally networked

Bourland’s team is in contact with Stefan Pelzer in Germany on an almost weekly basis. “For example, if we have substances that we think are interesting for the microbiome, our colleagues test them for us. We work a lot on skin, while the Künsebeck team works a lot on the microbiome,” reports Bourland. Combining the two is a major goal for her as well. 

To achieve this, the Skin Institute is working together with various startups that investigate skin biology. “Our network is an important key to success as we search for new paths and innovations,” says Bourland. However, testing the microbiome on laboratory skin is still in its infancy. “The models are not yet representative of what actually happens on skin,” says Bourland, “but we’re working on it.”

She believes that many cosmetics on drugstore shelves will be microbiome-friendly in the foreseeable future. “The biggest challenge in their development will be to address as many microbiomes as possible, as these are very individual in nature,” says Bourland.

Evonik is networked worldwide to further explore this distinctiveness. The researchers from Künsebeck are also in contact with the Center for Microbiome Innovation at the University of California in San Diego, USA. In addition, there is the communication with cosmetics manufacturers who have their customers’ interests in mind. Whether in California, Singapore or Germany, there’s a clear common goal: In the future, scientifically proven care products will protect and support the skin microbiome in order to maintain health and enable optimal skin care—completely individually.

A machine fills yellow liquid into two test tubes in a holder,

Stefan Pelzer explains the research approach

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