Biosynthesis of odd-chain fatty alcohols in Escherichia coli

• Metabolic engineering of E. coli to produce odd-chain fatty alcohol (C11, C13, C15).
• Demonstrated tailored production of desired medium odd chain fatty alcohols.
• Tuning gene expression levels in up- and down-stream pathway to improve production.
• A highest reported titer of 1.95 g/L fatty alcohols in E. coli was achieved.

Engineered microbes offer the opportunity to design and implement artificial molecular pathways for renewable production of tailored chemical commodities. Targeted biosynthesis of odd-chain fatty alcohols is very challenging in microbe, due to the specificity of fatty acids synthase for two-carbon unit elongation. Here, we developed a novel strategy to directly tailor carbon number in fatty aldehydes formation step by incorporating α-dioxygenase (αDOX) from Oryza sativa (rice) into Escherichia coli αDOX oxidizes Cn fatty acids (even-chain) to form Cn−1 fatty aldehydes (odd-chain). Through combining αDOX with fatty acyl–acyl carrier protein (-ACP) thioesterase (TE) and aldehyde reductase (AHR), the medium odd-chain fatty alcohols profile (C11, C13, C15) was firstly established in E. coli. Also, medium even-chain alkanes (C12, C14) were obtained by substitution of AHR to aldehyde decarbonylase (AD). The titer of odd-chain fatty alcohols was improved from 7.4 mg/L to 101.5 mg/L in tube cultivation by means of fine-tuning endogenous fatty acyl-ACP TE (TesA′), αDOX, AHRs and the genes involved in fatty acids metabolism pathway. Through high cell density fed-batch fermentation, a titer of 1.95 g/L odd-chain fatty alcohols was achieved, which was the highest reported titer in E. coli. Our system has greatly expanded the current microbial fatty alcohols profile that provides a new brand solution for producing complex and desired molecules in microbes.