Biosurfactants

What is a Biosurfactant?

Biosurfactants are generally defined as low-molecular weight surface-active compounds produced from either bacterial or fungal sources. These compounds have many interesting properties which include the ability to reduce interfacial tensions; and form stable emulsions, gels and foams.

Biosurfactants are amphipathic compounds classified on their molecular structure and can be divided into glycolipids, lipopeptides and phospholipids. High-molecular weight surface-active compounds such as lipopolysaccharides are more often termed Bioemulsifiers.

Glycolipids

The Microbial Biotechnology Research Group at Ulster University mainly focuses on glycolipid type biosurfactants.

Rhamnolipids – composed of one or two rhamnose sugars conjugated to fatty acid side chains which can be either saturated or un-saturated consisting of 8-16 carbons in length. Rhamnolipids are predominantly synthesised by the Gram negative, opportunistic pathogen Pseudomonas aeruginosa. However, our group has been investigating rhamnolipid biosynthesis in other non-pathogenic bacteria such as Burkholderia thailandensis.

Molecular structure of a di-rhamnolipid produced by P. aeruginosa.

Sophorolipids – composed of the dimeric carbohydrate sophorose linked to a long-chain hydroxyl fatty acid through a glycosidic bond. Sophorolipids can be both acid or lactonic and are produced by yeast species such as Starmerella bombicola (previously named Candida bombicola).

Molecular structure of acidic and lactonic sophorolipids.

Mannosylerythritol lipids (MELs) – MELs are composed of fatty acids containing either 4-O- β-D-mannopyranosyl-erythritol or 1-O-β-D- mannopyranosylerythritol as the hydrophilic head group, attached to a variety of fatty acids. These compounds are produced by yeast species such as Pseudozyma.

Generic molecular structure of a Mannosylerythritol lipid type biosurfactant.

Applications

Surfactant compounds are utilised in a number of industrial processes, the majority of these surfactants are derived from the petro-chemical industry. Biosurfactants possess a number of advantages over synthetic surfactant compounds as they are less toxic and can be produced from renewable resources. Biosurfactants currently account for approx. 5% of the world surfactant market and are predicted to be worth $5.5 billion by 2022. Biosurfactants are currently utilised for bioremediation of hydrocarbon contaminated soil; microbial enhanced oil remediation (MEOR); detergents in home cleaning products; food additives and in the textiles industry. Biosurfactant have also been shown to have anti-microbial properties and are currently being investigated for usage as novel anti-microbial drugs.

Research Posters on Biosurfactants

Twigg et al. (2019). Characterisation of rhamnolipid production in a previously un-investigated marine Pseudomonad. Presented at Biosurfactants 2019, Stuttgart, Germany (October 2019).

Twigg et al. (2019). The riddle of rhamnolipid molecular biosynthesis. Presented at Biosurfactants 2019, Stuttgart, Germany (October 2019)

Tripathi et al. (2019). Characterisation of rhamnolipid production in a Marinobacter strain and a description of its potential antimicrobial properties. Presented at Biosurfactants 2019, Stuttgart, Germany (October 2019).