Trehalose Biosurfactants - Biosurfactants: Research Trends and Applications - page 197

8 Trehalose Biosurfactants
Nelly Christova and Ivanka Stoineva
CONTENTS
Introduction ............................................................................................................ 197
Trehalose Lipids ..................................................................................................... 198
Chemical Structures of Glycolipids Produced from Mycobacteria .................. 198
Chemical Structures of Glycolipids Produced from Rhodococcus ................... 201
Production .............................................................................................................. 202
Biosynthesis ...................................................................................................... 202
Carbon Source and Growth Conditions ............................................................204
Optimization of Production ...............................................................................206
Physicochemical Properties ................................................................................... 207
Physiological Role and Biological Activities ......................................................... 208
Potential Application of Trehalose Lipids.............................................................. 210
Conclusion ............................................................................................................. 211
References .............................................................................................................. 212
INTRODUCTION
Many prokaryotic and eukaryotic microorganisms can grow on compounds that are
poorly soluble in water and often are associated with the production of surface-active
compounds or biosurfactants. Biosurfactants comprise a diverse group of chemical
structures with amphiphilic character. Generally, the lipophilic parts of their mol-
ecules consist of long-chain fatty acids, hydroxyl fatty acids, or α-alkyl-β-hydroxyl
fatty acids, while the hydrophilic moieties can be carbohydrates, amino acids, cyclic
peptides, phosphates, carboxylic acids, or alcohols. Biosurfactants can be catego-
rized in five groups regarding their chemical composition: glycolipids, lipopeptides,
phospholipids, fatty acids, and polymeric biosurfactants. Biosurfactants can also be
grouped into two categories: low-molecular-mass compounds that lower surface and
interfacial tension and high-molecular-mass compounds that bind tightly to surfaces
(Rosenberg and Ron 1999).
The amphiphilic character of the surfactant molecules is responsible for their unique
properties. They appear to act preferentially at the interface between phases with differ-
ent polarity and hydrogen bonding, forming an ordered molecular film at the interface
and altering significantly the interfacial energy (Georgiou et al. 1992). Recent studies
show that whenever a microbe comes across an interface, biosurfactants play a signifi-
cant role in several biological processes such as motility, bacterial cell signaling, bio-
film formation, cellular differentiation, substrate accession, and bacterial pathogenesis
(Kitamoto et al. 2002; Lang 2002; Cameotra and Makkar 2004; Van Hamme et al. 2006).
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