Are biosurfactants actually surfactants? Thoughts and opportunities concerning microbial glycolipid amphiphiles

Monday, May 1, 2023

4:10 PM – 4:30 PM MDT

Room: 405

Presenting Author(s)

Niki Baccile, PhD (he/him/his)

Researcher
Sorbonne Université
Paris, Ile-de-France, France

Co-Author(s)

AP

Alexandre Poirier

PhD, Employed in private sector
Sorbonne Université, France
CS

Chloé Seyrig (she/her/hers)

PhD, PostDoc
Sorbonne Université, France

Abstract: For most surfactants and lipids, the relationship between the chemical structure and the self-organization properties in water are well-known under standard conditions of use (room temperature, no added solute, neutral pH). Such relationship, called the packing parameter, correlates the effective surface area of the headgroup to the volume and length of the aliphatic chain (J. Chem. Soc., Faraday Trans. 2, 1976, 72, 1525). However, as we have recently illustrated in a broad literature survey (Table 9 in Green Chem., 2021, 23, 3842), this rule does not always apply to most microbial glycolipids, for which structure-property predictions are somewhat speculative, or simply wrong. According to our experience on the self-organization features of tens of microbial glycolipid amphiphiles in water, we have found that very often the word “biosurfactant” is not appropriate to describe their behaviour. In the worst case, many molecules display a lipid- or even gelator-like behaviour. In the best case scenario, some of them display a double surfactant/lipid-like behaviour. In a specific case, we have even observed a unique chameleonic behaviour (J. Colloid Interface Sci. 2023, 630, 404), meaning that a given molecule is able to self-associate into nine different supramolecular morphologies at room temperature and under conditions of strong dilution ( > 95 wt% water). Such an odd behaviour, incomparable in the standard literature of head-tail surfactants and lipids, can be driven by pH, type of counterion but also the sense, or even the rate, of pH variation.

This presentation has the goal of showing the limits of biosurfactants intended as surfactants and opens to new opportunities offered by the multiphasic behavior of this class of molecules in view of possible high-end applications.