ABSTRACT

Surfactants are surface-active molecules that mediate the solubility of hydrophobic chemicals in aqueous media by forming micelles and emulsions that physically arrange to suspend hydrocarbons, solvents and metals in water. As such, these compounds have fundamental roles in chemical synthesis

CONTENTS

5.1 Introduction ................................................................................................ 127 5.1.1 Overview and State of the Art ..................................................... 127 5.1.2 Chemistry, Diversity and Production of Biosurfactants .......... 129 5.1.3 Types of Biosurfactants ................................................................. 129

5.1.3.1 Microbially Derived Biosurfactants ............................. 129 5.1.3.2 Plant-Derived Biosurfactants ......................................... 132

5.2 Production Media ...................................................................................... 135 5.2.1 Carbon Sources .............................................................................. 135 5.2.2 C/N Ratios ...................................................................................... 136 5.2.3 Growth Stage .................................................................................. 136 5.2.4 Genetics and Biosynthesis of Biosurfactant Production .......... 138

5.3 Uses of Biosurfactants for Waste Treatment .......................................... 139 5.3.1 Bioremediation of Hydrophobic Substances .............................. 139 5.3.2 Biostimulation Removal of Heavy Metals from

Contaminated Environments ....................................................... 141 5.4 Biostimulation and In Situ Production ................................................... 143 5.5 Conclusions ................................................................................................. 145 References ............................................................................................................. 146

and industrial processes in which they are used to physically separate and concentrate chemicals that are targeted for disposal, recycling or further processing. The most common uses of surfactants are as detergents to desorb oil and other hydrophobic chemicals from surfaces and suspend the contaminants in water during equipment washing. The second main use is as emulsifiers and demulsifiers to create or break emulsions that gather and concentrate hydrophobic chemicals and metals previously dispersed in water. Lastly, surfactants can be used to alter the bioavailability of chemicals to degrader microorganisms that are used for bioremediation of organic pollutants either in a bioreactor or for treatment of contaminated soils and sludges that are generated during industrial processes. Given all of these applications, studies on the properties of surfactants and their optimisation for specific applications comprise a large body of knowledge with hundreds of research articles published each year in dedicated journals on surfactant chemistry, which include both synthetically produced surfactants and biologically produced biosurfactants.