Microbial engineering for production of novel lipids

SIMÓN MENENDEZ-BRAVO, SANTIAGO COMBA, ANA ARABOLAZA AND HUGO GRAMAJO.

Congreso; IX Congreso de Microbiología General; 2013

Nowadays, there are considerable environmental and economic drivers that impulse the development of new and improved bio-based chemicals. Particularly, in view of the lubricant industry, vegetable oils (i.e. triacylglycerols, TAGs) are considered a good source of biolubricants. However, their main disadvantages are their poor low temperature fluidity behaviour and their sensitivity to oxidation at high temperatures. Wax esters have lubrication properties that are superior to ordinary vegetable oil due to their high oxidation stabilities and resistance to hydrolysis. Nevertheless, due to the high cost of obtaining wax esters from existing sources, their use is limited to specialized and high value product areas such as cosmetic, pharmaceutical and/or specialty lubricants. In this context, microbial-cell-factories are an attractive model for the production of specific products as it provides the opportunity to convert sustainable biomass into high value chemicals. The assembly of metabolic activities derived from different organisms allows the reconstitution of designed biosynthetic pathways for the production of novel molecules with chosen features. With the aim of producing novel lipids with improved lubricant properties, we propose the synthesis of multi methyl-branched wax esters (MMWEs) in Escherichia coli. The inclusion of methyl branches would disrupt the lipid packing ability of the hydrocarbon chains, thereby reducing the melting temperature of the oil without altering chemical stability. To accomplish this, we took advantage of the metabolic pathways involved in the biosynthesis of complex lipids in mycobacteria. We have assembled a minimal set of three enzymes based on a type I iterative polyketide synthase biochemistry for in vivo production of a variety of functionalized lipids in a genetically improved E. coli strain. The successful in vivo synthesis of MMWEs by recombinant E. coli was detected by thin layer chromatography and confirmed by HPLC coupled to nanospray tandem mass spectrometry. We also showed that the chemical diversity of the MMWEs produced can be modulated in function of the substrates utilized.