**2. Biosurfactants produced by MACA**

In addition to *Rhodococcus*, diverse members of the order *Corynebacteriales* have been reported to synthesise extra-cellular and cell-bound biosurfactants, including

#### **Figure 3.**

*The appearance of (a)* Gordonia amarae*, (b)* Rhodococcus erythropolis *and (c)* Tsukamurella spumae *on glucose yeast-extract agar after 7 days incubation at 30°C.*


*\*S, straight-chain saturated fatty acids; U, straight-chain unsaturated fatty acids; T, tuberculostearic acid. Adapted from [2].*

#### **Table 2.**

*Chemotaxonomic features of mycolate genera classified in the order* Corynebacteriales*.*

members of the genera *Corynebacterium*, *Dietzia*, *Gordonia*, *Mycobacterium*, *Nocardia*, and *Tsukamurella.* Species belonging to the genus *Rhodococcus* have been most extensively investigated and are known to produce different chemical types, including a variety of glycolipids. However, an interesting array of biosurfactant structures are synthesized by MACA including lipopeptides, oligosaccharide lipids, polymeric glycolipids, terpenoid glycosides, trehalose corynemycolates, trehalose mycolates and dimycolates, and trehalose lipid (THL) esters [13]. Example structures of the different types of biosurfactants produced by MACA are shown in **Figure 4**. The chemical structure of trehalose-containing glycolipids have perhaps

*Biosurfactant Production by Mycolic Acid-Containing Actinobacteria DOI: http://dx.doi.org/10.5772/intechopen.104576*

been studied in most detail. Several structural types have been reported including mono-, di- and tri-corynemycolates which have been characterised for species such as *Rhodococcus erythropolis*, *Rhodococcus ruber* and *Rhodococcus wratislaviensis* [14] and trehalose di-nocardiomycolates which have been characterised for *Rhodococcus opacus* [13]. The mycobacterial trehalose mycolates or di-mycolates (cord factors) are also thoroughly investigated given their role as modulators of mycobacterial pathogenesis and host immune response.
