Stabilization and De-Stabilization of (Membrane-)Proteins by Microbial Glycolipid and Lipopeptide Biosurfactants - in-vivo Relevance and Industrial Applications

Abstract

Glycolipid and lipopeptide biosurfactants are secondary metabolites which are produced and secreted by a wide range of both pathogenic and non-pathogenic microorganisms. Under optimal conditions production of biosurfactants can reach 400 g/L. In-vivo, biosurfactants interact with a wide range of functional proteins and biosurfactants also has the potential to substitute non-sustainable chemical surfactants in detergents where they interact with enzymes. It is therefore relevant to understand how biosurfactants in-vivo interact with functional extracellular proteins and also how biosurfactants interact with industrial detergent enzymes.Biosurfactants can denature globular proteins such as myoglobin and α-lactalbumin. Denaturation kinetics is however an order slower when compared to classical chemical surfactants such as SDS. Commercial detergent enzymes are not denatured and inactivated by biosurfactants. This is in contrast to chemical surfactants such as SDS. Biosurfactants are thus promising eco-friendly alternatives to chemical surfactants.Biosurfactants can promote and stabilize protein structure. Biosurfactants fold and stabilize outer membrane proteins. The thermal stability is however perturbed in anionic biosurfactants compare to non-ionic dodecyl maltoside which is often used for membrane protein stabilization.Upon infections, human proteins may be exposed to secreted microbial biosurfactants. Lysozyme, a defensive and antimicrobial human enzyme, is highly protease resistant. However in the presence of anionic rhamnolipid, produced by the opportunistic pathogen Pseudomonas Aeruginosa, the positive surface potential is neutralized and lysozyme becomes easily susceptible for both human and bacterial proteases. Rhamnolipid also promotes fibrillation of FapC, the main protein in Pseudomonas Aeruginosa functional amyloids. Rhamnolipid induces instant fibrillation and also morphological changes in FapC fibrils. Biosurfactants may thus play an important role in microbial biofilms and infections.In general, biosurfactants can interact with proteins in multifarious ways with fundamental, medical and industrial relevance.