GUIDO BOGNOLO

Independent consultant, Belgium

In the 1998 work “La chasse au canards (hunting ducks)” by Robert Lamoreux there is a verse that has become of common use among many French speaking people, including in those 50% of the Belgians of which I am part. It says “et au troisiéme jour le canard etait encore vivant (and on the third day the duck was still alive) essentially meaning that something that was surely going to happen (the duck should have been the guest of honour at the table of the X-mas lunch) did not happen.

Nothing applies better to describe the life cycle of biosurfactants.

The first reporting of biosurfactants is attributed to Bergstrom et al. who in 1946 observed (and reported) a somewhat strange matter that appeared in their experiments (it was later recognized to be a sophorolipid) (1). Sophorolipids were positively identified in 1949 by Jarvis et al. (2), and isolated by Gorin et al. in1951 (3). Subsequent work led to the identification of other glycolipids until eventually in 1968 came the discovery of surfactin by Arima et al. (4) in 1968. This flood of completely new surface active species created great excitement and enthusiasm.

But regrettably much of the excitement was fuelled by misinformation. Biosurfactants were portrayed as having exceptional surface and interfacial properties, superior mildness and biodegradability, in many, many cases the author(s) of the  publications did not even measure them, just reported what someone else did or said, who in turn had reported what someone else had done or said, etc., etc., etc. 

Surfactancy, mildness, biodegradability were often quoted in the vacuum: for surfactancy there was nearly no comparison with existing surfactants, or the very, very few who ventured in a comparison used irrelevant references (Tween 20 or 80 and sodium dodecyl sulphates were the favourite benchmarks, ignoring sulphonates and alcohols ethoxylates). Readings of surface tension of 30 mN/m and higher were considered outstanding ignoring that the petrochemical surfactants mostly used have surface tension of between 28 and 32 mN/m. Many biosurfactants were claimed to have low critical micelle concentration (CMC), a daring statement, given that the curves of surface tension versus concentration gave a gentle decreasing slope to the equilibrium surface tension, which happened at much higher concentration. But extrapolation of the curve, drawing a straight tangent line at an arbitrary point in the curve, in the region of low concentration and a horizontal line at equilibrium gave low values at the crossing point of the two lines, and that was considered good enough.

Even today academic articles talk of biodegradability and mildness by extrapolation: biosurfactants are natural products hence they must be biodegradable and mild, with limited support (if any) of actual experimental evidence.

The phenomenon has gone out of hands to the point that the serious academia has eventually (and rightly) reacted and called its own members to behave. I quote an exert of an excellent article of Twigg et al. “ A major issue facing the field of microbial surface-active compound research has been that the discovery and/or biotechnological application of new biosurfactant-producing organisms has been seen as an easy opportunity for a research project and subsequent publication. ]This has led to a multitude of papers in the literature that are not only of little scientific value but are also misleading through repeated citation……Leading researchers in the field have identified that many of these studies utilize ]techniques [that] are not precise and accurate enough, so some published conclusions might not be justified. Such studies lacking robust experimental evidence generated by validated techniques and standard operating procedures are detrimental to the field of microbially produced surface-active compound research (5).

The excitement for the almost daily discovery of new yeasts, fungi, bacteria capable of synthesising biosurfactants concealed the reality that the bioconversion process generally produced biosurfactants very slowly and in very low yields, at the best a few grams  after days of fermentation. Thus exorbitant production costs, thousands times that of conventional surfactants and extremely low quantities available for a realistic assessment of their possible applications.   Working to raise productivity, hence reducing costs and making available sufficient volumes for real in-use tests (as opposed to inferring potential benefits from an inadequate evidence) was low in the priority of  many academic, lured by the perceived glory of discovering new producing species.

For many years to follow academia put more effort in search for biosurfactants producing microorganisms and strains and to characterize the products with more and more sophisticated analytical methods. But very little went into trying to understand what benefits  these molecules could  offer in practice.

Not surprising then that for many years biosurfactants remained laboratory curiosities, and that excitement turned into disillusion. And there is nothing better than disillusion to create antagonism. At the time I was a young researcher in the applied research department in a chemical multinational who had been part of the initial excitement, but then also of the disillusion, and for years the simple mention of biosurfactants caused an immediate reaction of disdain.

How happened then that “au troisiéme jour le canard etait encore vivant”? It happened because the industry stamped-in. The industry is Evonik.

Evonik’s Nutrition & Care Division of Industrial Biotechnology had been for long an important source of growth and innovation. The Division had retained an unshakable commitment to biosurfactants and had conducted extensive research in their premises at Slovenská L’Upča (Slovak Republic). The results were sophorolipids and rhamnolipids produced in commercial volumes and sold at prices that were eventually competitive on a price-effectiveness basis to conventional surfactants. Sophance LA-A ™, Rewoferm RL ONE ™ and Rehance ONE ™ are the trade names of Evonik’s commercial biosurfactants.

The route to rhamnolipids was bumpy; first they are high foaming, a property much sought after in hand dishwashing and hair and body shampoos, but havoc in fermentation processes. This was solved by addressing process design and equipments, such that foam was no longer a limit to productivity. Second, among the many species producing rhamnolipids only the pathogenic Pseudomonas aeruginosa produced high yields. This demanded a lengthy and expensive purification process to ensure that any residue of the bacteria was removed. The problem was solved by genetic engineering, transposing the genes responsible for the rhamnolipids synthesis in Pseudomonas aeruginosa into the non-pathogenic Pseudomonas putida (6). The result was high yield of biosurfactant produced safely.

As of 2018 Evonik began to supply Unilever with the volumes needed to formulate a hand dishwashing liquid put in the Chilean market under the trade name “Quix”. Another hand dishwashing products containing rhamnolipids, trade name “Sunlight” was marketed in Vietnam. In 2019 Evonik and the consumers group of Unilever entered in a strategic alliance.  Unilever had already taken steps towards sustainability with the Clean Future Initiative, with the set goal “to replace fossil carbon in all cleaning products by 2030” (7).

Was the Evonik faith that convinced other to follow, or the mounting pressure of the public opinion for a green planet and the growing concern about climate changes?

Up to you to judge, but look at the situation today.

BASF has a capital and business agreement with the biosurfactants producer ACS of Japan.

On January 25, 2022Dow announced an exclusive engagement with Locus Performance Ingredients of the USA to sell its line of sophorolipids in the global home care and personal care markets.

In March 2022 Sasol Chemicals entered in partnership with Holiferm Ltd. (UK) to develop and commercialize sophorolipids. On 25 January, 2023 Holiferm and Sasol announced a further collaboration to produce and market rhamnolipids and mannosylerythritol lipids. The agreement includes a commitment from Sasol to purchase the majority of the production from the new Holiferm plant due to be operational by mid 2023. In October 2023 Sasol launched two brands, Carinex™ for personal care and Livinex ™ for the home care, technical, institutional and industrial cleaning that uses sophorolipids manufactured with Holiferm’s proprietary technology.

In March 2022 Stepan purchased the rhamnolipid technology of NatSurFact ® from Logos Technologies Inc. of the USA and is supplying samples to NatSurFact’s existing customers. It has plans for expanded production. Jointly with Jeneil, Stepan markets the rhamnolipid-based Zonix ™ fungicide for the agricultural market.

Above these majors, about 35 biosurfactants producers around the world have been positively identified, and the number increases by the day as large multinational and venture capital investors take an interest in shadow enterprises that have the technology but not the cash to organize production.  

Producing means nothing if there are no sales. Here it is more difficult to identify participants, but a few facts can be quoted.

The personal care industry has been the first to respond to the siren song of biosurfactants. In the USA by mid 2023 there were at least 97 creams, 51 serum and 49 shampoos brands containing “Glycolipids” (the INCI name that lumps together all the existing glycolipids).  The formulated products include shampoos, moisturizers, micellar water, baby products hand cleaners. In China the brand’s adoption of “Glycolipids” increased over 10 times in the last five years.

The use of  biosurfactants in hand dishwashing liquids  extends beyond the brands already discussed. There are producers in China and Japan. In Europe Ecover who were the first to sell a household cleaner containing biosurfactants in 2009 have a full range of cleaners, differing in size and concentration.

There are now formulated products on sale for oil cleaning, diary hard surface and equipment cleaning, hatcheries and growing barns cleaning, animal husbandry, animal feeding, fungicides.

It appears then that biosurfactants are exiting the darkness of the early 2000s for a brighter future. But it is worth keeping in mind that naturally occurring surfactants, including biosurfactants will never be a complete substitute for the conventional surfactants. And this for the simple reason that the vast majority of naturally occurring surfactants are nonionic  while conventional surfactants,  are nonionic, anionic, cationic and amphoteric. Sophorolipids are a mixture of anionic carboxylates and nonionic lactones, while the  few natural anionics (phospholipids) do not have the structure, and hence the performance matching that of the of conventional anionics. 

The production cost of biosurfactant, although orders of magnitude lower than in the early days, leaves still room for further improvements. The microorganisms producing Evonik’s rhamnolipids feed on glucose which is not cheap and has alternatively nutritional use. Other research work suggests that sunflower oil or other edible oils or hydrocarbons could become acceptable feedstock.

Using household or industry wastes is sighted as the perfect solution that contributes both to the cheap production of biosurfactants and to the circular economy. Regrettably the results to-date are deceiving: different wastes, from spent cooking oils to olive pressing residues to citrus or orange peels did not produce acceptable yields.

You can imagine my excitement when reading that a leading biosurfactants formulator had announced the test marketing of two products using material recovered from industrial wastes. The colourful promotional leaflet in support of the test market shows pictures of typical wastes, potatoes and apples peels and banana skins, makes references to biosurfactants for a greener world  and prises the contribution of waste recovery to the circular economy.  I could not control my emotions “wuuaaaahhhh, finally there is a cost-effective way to  produce economically biosurfactants from waste” was my emotional reaction. The enthusiasm however chilled when consulting other publications of the same company to find out more of what in my interpretation was an extraordinary endeavour, I read that the waste recovered were water and ethanol. Now these are typical ingredients for any formulation, irrespectively if it has to do with conventional surfactants or biosurfactants. Good, every gram of waste recovered is a gram gained, but why associating to biosurfactants something that has nothing to do with biosurfactants? Surely there were other ways to present a positive achievement without playing on ambiguities.

Biosurfactants can do without it.