ABSTRACT
Succinoyl trehalose lipids (STLs) are promising glycolipid biosurfactants produced from n-alkanes that are secreted by Rhodococcus species bacteria. These compounds not only exhibit unique interfacial properties but also demonstrate versatile biochemical actions. In this study, three novel types of genes involved in the biosynthesis of STLs, including a putative acyl coenzyme A (acyl-CoA) transferase (tlsA), fructose-bisphosphate aldolase (fda), and alkane monooxygenase (alkB), were identified. The predicted functions of these genes indicate that alkane metabolism, sugar synthesis, and the addition of acyl groups are important for the biosynthesis of STLs. Based on these results, we propose a biosynthesis pathway for STLs from alkanes in Rhodococcus sp. strain SD-74. By overexpressing tlsA, we achieved a 2-fold increase in the production of STLs. This study advances our understanding of bacterial glycolipid production in Rhodococcus species.
Subject(s)
Glycolipids/biosynthesis , Rhodococcus/genetics , Trehalose/biosynthesis , Alkanes/metabolism , Coenzyme A-Transferases/genetics , Coenzyme A-Transferases/metabolism , Cytochrome P-450 CYP4A/genetics , Cytochrome P-450 CYP4A/metabolism , DNA Transposable Elements , DNA, Bacterial/genetics , Fructose-Bisphosphate Aldolase/genetics , Fructose-Bisphosphate Aldolase/metabolism , Genes, Bacterial , Molecular Sequence Data , Plasmids/genetics , Rhodococcus/enzymology , Sequence Analysis, DNAABSTRACT
Succinoyl trehalose lipids (STLs) are promising glycolipid biosurfactants produced from n-alkanes by Rhodococcus sp. These compounds show not only unique interfacial properties but also versatile biochemical actions. In this study, we determined for the first time the complete structure of the main component, namely STL-1, based on NMR, MALDI-TOF/MS and GC-MS analyses. The present STL-1 produced from n-hexadecane was identified as 3,4-di-O-alkanoyl-2-O-succinoyl-alpha-D-glucopyranosyl-2'-O-succinoyl-alpha-D-glucopyranoside. The major fatty acid of STL-1 was C(16), indicating that n-hexadecane as the carbon source is directly incorporated into the carbohydrate moiety via terminal oxidation. We also investigated its surface active properties using a Whilhelmy method at 25 degrees C. The estimated CMC and gamma(CMC) values for STL-1 were 5.6x10(-6) M and 19.0 mN/m, and those for sodium salt (NaSTL-1) were 7.7x10(-6) M and 23.7 mN/m, respectively. The high activity of STL-1 was probably due to the unique molecular structure resulting from its multiple functional groups including succinic acids and two long fatty acids. Accordingly, STL-1 and its sodium salt were demonstrated to exhibit an excellent surface-activity at remarkably low concentrations, and should have great potential for environmentally friendly surfactants.
