Abstract
SummaryThe AlkBGTL proteins coded on the alk operon from Pseudomonas putida GPo1 can selectively ω‐oxidize ethyl esters of C6 to C10 fatty acids in whole‐cell conversions with Escherichia coli. The major product in these conversions is the ω‐alcohol. However, AlkB also has the capacity to overoxidize the substrate to the ω‐aldehyde and ω‐acid. In this study, we show that alcohol dehydrogenase AlkJ and aldehyde dehydrogenase AlkH are able to oxidize ω‐alcohols and ω‐aldehydes of esterified fatty acids respectively. Resting E. coli expressing AlkBGTHJL enabled exclusive mono‐ethyl azelate production from ethyl nonanoate, with an initial specific activity of 61 U gcdw −1. Within 2 h, this strain produced 3.53 mM mono‐ethyl azelate, with a yield of 0.68 mol mol−1. This strain also produced mono‐ethyl dicarboxylic acids from ethyl esters of C6 to C10 fatty acids and mono‐methyl azelate from methyl nonanoate. Adding ethyl nonanoate dissolved in carrier solvent bis‐(2‐ethylhexyl) phthalate enabled an increase in product titres to 15.55 mM in two‐liquid phase conversions. These findings indicate that E. coli expressing AlkBGTHJL is an effective producer of mono‐esterified dicarboxylic acids from fatty acid esters.
Highlights
Medium-chain a,x-dicarboxylic acids (DCAs) are building blocks for polyesters, polyurethanes and polyamides
The expansion of the AlkBGTL pathway with AlkJ and AlkH in E. coli resulted in a biocatalyst that could efficiently x-oxidize ethyl-esterified medium-chain fatty acids to yield mono-ethyl DCAs
Aldehyde dehydrogenase AlkH produces the carboxylic acid from 9-oxo methyl nonanoate
Summary
Medium-chain a,x-dicarboxylic acids (DCAs) are building blocks for polyesters, polyurethanes and polyamides. Adipic acid (AA), a C6 DCA, is produced from the petrochemical feedstock benzene. To produce AA, benzene is converted into a mixture of cyclohexanol and cyclohexanone. This mixture is oxidized with nitric acid to yield adipic acid with the concomitant emission of N2O, a potent greenhouse gas (Cavani and Alini, 2009; Van de Vyver and Roman-Leshkov, 2013). C8-C10 DCAs are produced from renewable feedstocks, such as oleic acid and ricinoleic acid, via ozonolysis (Cornils et al, 2000; Metzger, 2009). Ozonolysis of unsaturated fatty acids is highly selective and effective, it suffers from several drawbacks. The applied ozone is highly toxic and associated with high explosion risks. The cleavage of unsaturated fatty acids results in by-product formation
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
