Page 129 - CW E-Magazine (2-7-2024)

Point of View

Microbial biosurfactants likely set for a virtuous

cycle of growth

Microbial biosurfactants (MBS), in contrast to chemical surfactants, are surface-active substances synthesized by living cells. They are
amphiphilic compounds produced on living surfaces, mostly microbial cell surfaces, or excreted extra-cellularly and contain hydrophobic and
hydrophilic moieties that reduce surface tension and interfacial tensions between individual molecules at the surface and interface, respectively.

Interest in MBS has been steadily increasing in recent years due to their diversity, environmentally friendly nature, possibility of large-
scale production, selectivity, performance under extreme conditions and potential applications in environmental protection.

The type and amounts of MBS produced depend primarily on the producer organism, factors like carbon and nitrogen, trace elements,
temperature and aeration.
Classification
MBS are classified mainly by their chemical structure and microbial origin. Structurally, they contain a hydrophobic and hydrophilic
moiety. The hydrophilic (polar) moiety (water soluble) can be a carbohydrate, an amino acid or peptide, a phosphate group, alcohol, carboxylic
acid or some other compound, while the hydrophobic (non-polar) moiety (oil soluble) is mostly a long-carbon-chain fatty acid (saturated or
unsaturated).

MBS are part of a broader family of biosufactants, the first generation of which include the well-known alkylpolyglucosides (APGs),
made entirely from renewable feedstocks (starch and vegetable oils based fatty acids) through chemical synthesis (though they can also
be made enzymatically). APGs are now established and used mainlyin personal care and cleaning applications, though their current market
size is well below early projections. Newer first generation biosurfactants include sucrose esters, produced by chemically esterifying fatty
acids with sucrose.

MBS represent the second generation of biosurfactants and are the latest wave in surfactants. Several are possible, and some are now
being produced at commercial scale by fermentation principally from oils, fats, and sugars. They include lipopeptides and oligopeptides,
glycopeptides (such as sophorolipids and rhamnolipids), polymeric biosurfactants, and phospholipids.Glycolipids are the most well-known
MBS. They consist of mono-, di-, tri- and tetra-saccharides and include glucose, galactose, mannose, rhamnose and glucuronic acid. Among
glycolipids the best known are sophorolipids, trehalolipids and rhamnolipids.

Sophorolipids were the first MBS to enter the beauty and personal care market. They are produced by yeasts and occur naturally in
materials such as some types of honey. A select number of yeasts such as candida bombicola can be used industrially to produce
sophorolipidsfrom raw materials such as sugar and rapeseed oil. Rhamnolipids are glycolipids naturally produced by Pseudomonas aeruginosa
in oily media. They have strong foaming properties and are very mild on the skin and the environment and are also suitable for use in oral
care products like toothpaste and mouthwash, as well as baby care products.

Sophorolipids are the largest category of MBS in use today, accounting for more than 50% of the global MBS market, followed by the
rhamnolipids.

Benefits
MBS have several advantages over their chemical counterparts. They are free of palm oil, which keeps them away of the criticism of
deforestation, as well as human rights and labour issues associated with palm oil derived products that have (part) biological origin. From a
perspective of functional properties, MBS are mild, readily biodegradable, and with low aquatic toxicity. Traditional surfactants, on the other
hand, are oil-based chemicals (which raises sustainability issues) and could have environmental concerns since they are eventually released
in the environment through wastewaters.

Importantly, MBS typically have up to 50% lower carbon footprint compared to existing fossil and partially fossil-basedand palm kernel
oil (PKO)-based surfactants. There are no dioxane issues associated with their manufacture (a problem increasingly impacting markets
for ethoxylated surfactants), and their use enables sulphate-free and non-GMO claims in personal care products wherein they are most
commonly employed. MBS also have superb synergy as a co-surfactant with other bio-based surfactants.

Chemical Weekly July 2, 2024 129

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