Sustainable microbial biosurfactants and bioemulsifiers for commercial exploitation

Emulsion-based formulations are widely exploited in medicine, food and cosmetics, where surfactants and emulsifiers play contrasting, but equally important roles. Both are able to adsorb at the oil and water interface enabling dispersion of droplets of one phase in the second. The main function of surfactants is lowering the interfacial tension, while emulsifiers, adsorb more slowly to the droplet surface and give longer-term stability. High toxicity and high ecological impact of many synthetic surfactants/emulsifiers have led to interest in other, natural molecules such as biosurfactants and bioemulsifiers. These bio-based surface-active agents are interesting for the main industries linked to human health – pharmaceuticals, food and cosmetics, with several having been discovered and already widely applied. However, the commercialisation of the production of bio-surfactants/emulsifiers is often limited by optimisation difficulties, high purification costs and low yields, all of which have an impact on their wider application. Therefore, much effort is required to find stable and cost effective methods to produce bio-surfactants/emulsifiers on a large scale. This review focuses on the main properties of bio-emulsifiers and bio-surfactants, followed by an overview of their current use in consumer product formulations. Finally, the potential of bio-surfactants/emulsifiers to replace the currently used counterparts will be assessed.