We have developed the conversion of glycerol into thermoplastic poly(3-hydroxypropionate) [poly(3HP)]. For this, the genes for glycerol dehydratase (dhaB1) of Clostridium butyricum, propionaldehyde dehydrogenase (pduP) of Salmonella enterica serovar Typhimurium LT2, and polyhydroxyalkanoate (PHA) synthase (phaC1) of Ralstonia eutropha were expressed in recombinant Escherichia coli. Poly(3HP) was accumulated up to 11.98% (wt/wt [cell dry weight]) in a two-step, fed-batch fermentation. The present study shows an interesting application to engineer a poly(3HP) synthesis pathway in bacteria.
Petroleum (or crude oil) is a complex mixture of hydrocarbons. Annually, millions of tons of crude petroleum oil enter the marine environment from either natural or anthropogenic sources. Hydrocarbon-degrading bacteria (HDB) are able to assimilate and metabolize hydrocarbons present in petroleum. Crude oil pollution constitutes a temporary condition of carbon excess coupled to a limited availability of nitrogen that prompts marine oil-degrading bacteria to accumulate storage compounds. Storage lipid compounds such as polyhydroxyalkanoates (PHAs), triacylglycerols (TAGs), or wax esters (WEs) constitute the main accumulated lipophilic substances by bacteria under such unbalanced growth conditions. The importance of these compounds as end-products or precursors to produce interesting biotechnologically relevant chemicals has already been recognized. In this review, we analyze the occurrence and accumulation of lipid storage in marine hydrocarbonoclastic bacteria. We further discuss briefly the production and export of lipophilic compounds by bacteria belonging to the Alcanivorax genus, which became a model strain of an unusual group of obligate hydrocarbonoclastic bacteria (OHCB) and discuss the possibility to produce neutral lipids using A. borkumensis SK2.
Triacylglycerols (TAG) and wax esters (WE) constitute together with polyhydroxyalkanoates (PHA) the major storage lipophilic compounds in prokaryotes. Recently, the production of neutral lipids such as TAG and WE has been reported in species of the genus Alcanivorax, which belongs to the group of obligate hydrocarbonoclastic bacteria (OHCB). We analyzed the production of such neutral lipids by different marine hydrocarbonoclastic bacteria growing on pyruvate or hexadecane as sole carbon source, and compared it to other bacteria such as Rhodococcus opacus strain PD630 and Acinetobacter baylyi strain ADP1, which are two well-studied strains for production of neutral lipids. Alcanivorax borkumensis SK2 synthesized mainly TAG when cells are cultivated on pyruvate, while biosynthesis and accumulation of WE was mainly observed in cells growing on hexadecane. Alcanivorax jadensis T9 synthesized and accumulated mainly WE if cells were cultivated with hexadecane, while both TAG and WE were observed if cells were cultivated with pyruvate as sole carbon source, respectively. Predominantly production as well as export of WE was observed in Marinobacter hydrocarbonoclasticus SP17 growing on pyruvate or hexadecane as sole carbon source. The chemical structures of TAG and WE produced by A. borkumensis SK2 were analyzed by gas chromatography and/or mass spectrometry, and first studies to investigate the influence of different C/N ratio (7, 50 or 150) on the production of neutral lipids were performed.
In many microorganisms, the key enzyme responsible for catalyzing the last step in triacylglycerol (TAG) and wax ester (WE) biosynthesis is an unspecific acyltransferase which is also referred to as wax ester synthase/acyl coenzyme A (
This study presents novel information useful for addressing the question how species of the genus Alcanivorax discharge triacylglycerols (TAG) and/or wax esters (WE). The observed structures were referred as ''blebs'' according to Gauthier et al. [1] to avoid confusion with other discharging phenomena. The cells were aerobically cultivated on solid media and not in liquid media to maintain the cells in the native state, and were investigated by transmission electron microscopic (TEM) and scanning electron microscopic (SEM) methods to document the surface structures of the cells. The phenomenon of lipid export could be allocated to three phases: phase I: protrusion formation of the cell membrane occurred; phase II: discharging progressed further with blebs becoming larger; and phase III: the blebs at the cell surface were separated from the cells. Using freeze-fracture micrographs by TEM, vesicle experiments and TLC, we have shown that the blebs contained TAG and WE. The results shown in this study will support further research to unravel the unknown discharging mechanism. In addition, the formation of an extensive extracellular matrix was observed by SEM.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.