Dominic Büning of Sasol Chemicals explains the challenges and opportunities of developing and commercializing multifunctional biosurfactants, which perform in various personal care applications, for a mass market adoption of technology

Surfactants play a critical role in the personal care industry. They act as cleansing agents, dispersants, thickening agents, emulsifiers, foaming agents, solubilizers, wetting agents and more.

For example, surfactants are used as emulsifiers within many daily leave-on products like creams, lotions and sunscreens, where they stabilize two or multiphase systems of immiscible liquids. As key ingredients in every rinse-off formulation, such as facial cleansers, shampoos and shower gels, surfactants are used to cleanse the hair, scalp and skin effectively.

Thus, these ingredients significantly contribute to our daily hygiene routine. Furthermore, they are also known for their encapsulating properties for other waterinsoluble ingredients, such as essential oils and perfumes.

Despite offering these various functions and fascinating features, there are a few reasons why the industry needs advanced surfactant alternatives

First, some traditional surfactants can cause irritation and itchiness to the scalp and skin, which is particularly relevant for sensitive users of daily personal care products and rinse-off power users like professional hairdressers or medical staff who frequently come in contact with these formulations throughout the day.

For this reason, there has always been a market pull towards more mild surfactant systems and the resulting formulations. Ideally, these systems should also help moisturize and protect the skin barrier function, ultimately limiting transepidermal water loss.

Second, innovative ingredients should be able to unlock premium performance that allows formulators to address important consumer needs and today’s major industry trends. For example, multifunctional surfactants that combine foaming and mild cleansing action with skin and scalp care properties are in line with the current trend towards a more minimalistic formulation approach and higher efficiency.

Third, the production of surfactants is traditionally based on petrochemical, palm kernel oil (PKO) and/or coconut oil (CNO)- derived feedstocks, some of which account for significant carbon emissions and other adverse effects on the environment such as deforestation and biodiversity loss in tropical regions

With the push to meet net-zero emissions and increasing environmental social governance (ESG) requirements, an ever-growing number of consumers and manufacturers are highly conscious of the ecological footprint of daily personal care products. This induces a rising demand for more sustainable ingredients in the cosmetic industry.

Future ingredients should therefore aim to be based on renewable and sustainably sourced feedstocks. They should be safe for humans and the environment, be completely biodegradable, have a lower product carbon footprint and ideally feature novel exciting properties.

With these considerations, fermentation-derived biosurfactants represent an important upcoming class of sustainable ingredients for innovative personal care formulations

These biodegradable, very mild and multifunctional ingredients combine classical surfactant properties with advanced scalp and skin care as well as microbiome-related benefits.1 This article discusses how these fossil- and palm-free alternatives are becoming more widely used in the industry.

Click to PCM to read full article

Classes of bio-based surfactants and sustainability considerations

Before approaching the topic, it is important to recall the different terminology between bio-based surfactants and biosurfactants. Per definition, bio-based surfactants broadly refer to surfactants that are partially or fully based on renewable feedstocks. This material class can be divided into three sub-segments: Partially biobased surfactants, fully bio-based surfactants and biosurfactants.

Partially bio-based surfactants typically consist of an alkyl chain derived from PKO- or CNO-based fatty acids as a hydrophobic building block which is coupled with a petrochemicalderived hydrophilic building bloc

For example, fatty alcohol ethoxylates are typically based on natural fatty alcohols and petrochemical-derived ethylene oxide (EO) despite recent industry initiatives to transform the EO value stream towards biomass on a massbalanced or even segregated basis. Because of their compatibility, these materials are widely used as weak to moderate foaming cosurfactants, mainly in combination with anionic surfactants, in personal cleansing products such as shampoos, shower gels or liquid soaps

In addition to their use as surfactants, fatty alcohol ethoxylates serve as raw material for the manufacturing of important anionic surfactants such as alkyl ether sulfates (AES) like sodium laureth sulfate (SLES) or alkyl ether carboxylates. Partially bio-based surfactants are therefore considered as the current standard of the industry because the materials are cheap, biodegradable, insensitive to water hardness and relatively mild to the skin despite their good cleansing and foaming performance.

Fully bio-based surfactants are solely based on renewable feedstocks, which also includes the aforementioned ethoxylates and derivates based on bio-ethylene. Here, the hydrophilic building block is derived from natural feedstocks such as sugars and amino acids, or inorganic molecules like sulfur trioxide.

Important examples for fully bio-based surfactants are alkyl sulfates (AS), alkyl polyglycosides (APG) and amino acid-based surfactants such as glycinates, sarcosinates, taurates and isethionates. These materials are typically more sensitive to water hardness, offer less foaming functionality and are more expensive, compared to partially bio-based surfactants.

Interestingly, there are some fully bio-based surfactants like AS, including Sodium Lauryl Sulfate (SLS) and alpha-olefin sulfonates (AOS), which are harsher and do not offer optimal performance compared to classical SLES.

While bio-based surfactants result partially or fully from renewable raw materials, this does not necessarily translate to a lower carbon footprint compared to petrochemicals. This is somewhat counterintuitive as fossil-based materials – per definition – feature a biogenic carbon uptake of zero.

For illustration, cradle-to-gate life cycle assessment (LCA) studies by Shah et al show natural fatty alcohols based on palm kernel oil may have a higher overall carbon footprint compared to synthetic alcohols due to greenhouse gas emissions associated with deforestation and land-use-changes.²

This example, among others, shows that the industry needs to further broaden the LCA database and understanding to identify and pursue the most sustainable feedstock and value

stream options on a scientific basis. To create a coherent understanding, this initiative cannot be limited to personal care but should be based on cooperation between various partners along the value chain and across different industries.

A closer look at biosurfactants

Given the ecological challenges with petrochemical-based surfactants and even conventional bio-based surfactants, various researchers in academia and in the industry have been working on alternative solutions.

While biosurfactants have been used as active ingredients within niche applications, they have only recently become more commercialized by various manufacturers, making them more affordable and available in higher volumes. Thus, they are among the latest innovations in a long line of sustainability efforts by the surfactant industry.

Unlike their chemically derived counterparts, these naturally occurring surfactants are produced by fermentation using microorganisms. Interestingly, they are produced as secondary metabolites by a wide range of different organisms, like bacteria, fungi, and yeast, for numerous reasons

Examples include making hydrophobic substrates more accessible, i.e. digestible, reducing the competition from other organisms through antimicrobial action and/or disrupting biofilm formation by preventing cell adhesion. Because these surfactants are fully derived from locally grown feedstocks such as natural oils and/or sugars, they are a more sustainable product with a lower product carbon footprint compared to classical petrochemical or bio-based surfactants.

However, the product carbon footprint of those materials is clearly dependent on the raw material input as well as energy demand during the fermentation and the subsequent downstream process.

Most importantly, the production of these materials is not associated with the depletion of fossil resources nor biodiversity loss or deforestation issues that are discussed for classically used lauric oils, like PKO, derived from tropical regions. Furthermore, the biosurfactant production process offers an exciting opportunity to be incrementally transitioned from using first-generation biomass including vegetable oils and sugars to second-generation biomass such as wood, towards third-generation biomass such as food waste, as a feedstock

However, it is worth noting that there is consensus within the industry to broaden the LCA database and develop a coherent understanding of the sustainability aspects of these different options.³

From a formulation perspective, biosurfactants are often not drop-in replacements for traditional, petrochemical-base surfactants, which becomes apparent from their different molecular structure, and might require some new formulation approaches. While state-of-the art formulation concepts have been successfully optimized over decades, these novel ingredients have only recently gained significant focus and attraction by the industry

However, when successfully implemented, these reformulations may unlock a new realm for personal care products, contributing, for example, to mild cleansing properties, hair conditioning, skin moisturization and more beyond the capabilities of classical ingredients.

Click to PCM to read full article

Types of biosurfactants and their benefits

Among most commercially advanced biosurfactants are glycolipids, including rhamnolipids and sophorolipids, and to a certain extent, mannosylerythritol lipids (MELs). Glycolipids are of particular interest for rinse-off formulations such as hand soap, shampoo, conditioner, mouthwash, make-up removers, anti-acne gels, facial cleansers, and toothpaste.

These multifunctional ingredients are mild to skin and eyes, contribute to cleansing and foaming performance and feature exciting and perceivable skin and scalp care properties. Furthermore, these biosurfactants beneficially affect the human skin microbiome in a variety of ways.1

Rhamnolipids, a subgroup of glycolipids, are produced by fermentation using Pseudomonas aeruginosa bacteria that consume sugar and/ or rapeseed oil, depending on the process and strain. There are two structural types: monorhamnolipids and di-rhamnolipids, which consist of one or two hydrophilic rhamnose groups respectively, which again can be tailored.

However, there are two challenges. Pseudomonas is a human pathogen and must be deactivated and removed from the finished product. They also produce low production yields, making rhamnolipids difficult to produce, yet an increasing number of companies now produce them on a commercial scale.

Sophorolipids, also a subgroup of glycolipids, are produced by fermentation using Starmerella bombicola yeast that consumes glucose and rapeseed oil. These biosurfactants consist of a hydrophilic acetylated and/or nonacetylated sophorose segment that is attached to a hydrophobic differently unsaturated lipid chain with a terminal carboxylic acid function

These molecules either form a closed lactone ring via internal esterification or are present with a free carboxylic acid group, which turns the molecule from a nonionic into an anionic surfactant. It should be noted that commercially available products always contain a mixture of lactonic and acidic sophorolipids

For example, the sophorolipid product range, recently launched by Sasol, consists of two 60% active product types including a lower foaming high-lactonic sophoropipid type (CARINEX SL L) and a higher foaming highacidic sophorolipid type (CARINEX SL A), see Figure 1. Scientific studies showed sophorolipids to feature a beneficial antimicrobial (bacteriostatic) effect against Cutibacterium acnes (formerly known as Propionibacterium acnes) that inhibits their proliferation on skin

Furthermore, sophorolipids feature a high microbiome and skin compatibility as well as skin moisturization properties.1 However, it is likely that there is a synergistic effect of these benefits in vivo on human skin, which is not necessarily apparent when conducting classical in vitro experiments. Furthermore, sophorolipids are described as active against dandruff on dry and oily scalps

Mannosylerythritol lipids (MELs) are another subgroup of glycolipids, consisting of a hydrophilic sugar core of 4-O-β-Dmannopyranosyl-D-erythritol with multiple hydrophobic residues. Typically, those include two fatty acid chains with different degrees of acetylation.

Depending on the acetylation degree and position, they are distinguished between MEL-A, MEL-B, MEL-C and MEL-D with an increasing polarity from MEL-A towards MEL-D. In cosmetic formulations, MELs are mostly used for damaged hair repair. Because they also show interesting properties in regard to skin moisturization, and barrier repair they are an interesting alternative for ceramides.¹

Overall, biosurfactants can offer a variety of exciting scalp, skin, and hair care benefits. However, biosurfactants feature very different molecular structures compared to traditional surfactants that allow for, but also need, novel formulation design approaches. For example, these materials are more compatible with cationic surfactants and polymers than classical surfactants, although featuring anionic groups

However, when determining the best biosurfactant solution, it is important for formulators to work directly with raw material manufacturers so they understand the product type, current surfactants being used and the benefits they are looking for. There is no single set formulation for certain kinds of products, so consultation is often required to discuss customization and other adjustments that will produce the desired benefits and optimal performance in final products.

Click to PCM to read full article

Key to innovation: collaboration

While commercial biosurfactants have been around for several decades, the primary barriers for a widespread adoption of the technology within the personal care industry are cost of production, performance linked to the raw material quality and purity and scalability of production

Only recently have significant technological improvements of the downstream process, which involves separating and purifying the biosurfactants out of the fermentation broth, come to fruition. Thanks to these improvements, the production of biosurfactants has become more economically available and scalable.

On the formulation side, there are similar challenges associated with the widespread use of biosurfactants. Manufacturers are faced with creating new formulation designs while ensuring scalability, affordability, and optimal performance.

Biosurfactants have not reached full mass market volumes yet, which is why formulators view them as more expensive than conventional surfactants. However, prices are expected to change as raw material producers obtain economies of scale and further optimize production processes

As raw material manufacturers continue to work on the ramp-up of production capacities and the development of new biosurfactants variants, producers of consumer products are more focused on the establishment of understanding formulation and adopting biosurfactants in known formulations.

There is a risk that the industry is currently running into the problem of innovation silos, as individual teams are stuck in innovation cycles focusing exclusively on individual product lines or parts of the value chain. From an innovation strategy perspective, these silos limit the ability of the personal care industry to go through a substantial sustainability-driven transformation, including the adoption of potentially disruptive technologies like biosurfactants

Given the ambitious sustainability targets of all major industry players for the upcoming years and the potential contribution of this technology to achieve those goals, there is no time to waste

The industry needs a fundamental shift in how it has largely operated over the last few decades. It requires collaboration between various companies, start-ups, and universities to drive this technology forward.

Partners need to be willing to jointly work on formulation design guidelines, application data and molecular structure performance relationships to ensure the future growth of biosurfactants. As an example, in March 2022, Sasol Chemicals began working closely with a partner on the commercialization of biosurfactants beyond sophorolipids.

Conclusion

Overall, while work continues to improve existing biosurfactants and incorporate them into formulations, there are many benefits to adopting this new ingredient into future products. However, companies should keep in mind this will require an open mind, collaboration, and patience with changing existing formulations to create more sustainable products.

The overall goal for the industry is to create personal care products with lower carbon footprints while unlocking premium performance and addressing consumer needs and evolving industry trends. Sasol Chemicals is working to commercialize various multifunctional biosurfactants that perform in various personal care applications, aiming for a mass market adoption of technology.

Every household should have access to sustainable products for their personal care needs, and biosurfactants are becoming a key ingredient in these products.

References

Click to PCM to read full references