High cell density production of multimethyl-branched long-chain esters in Escherichia coli and determination of their physicochemical properties.

MENENDEZ-BRAVO S, ROULET J, SABATINI M, COMBA S, DUNN R, GRAMAJO H, ARABOLAZA A

BIOTECHNOLOGY FOR BIOFUELS

BIOMED CENTRAL LTD

Lugar: Londres; Año: 2016

1754-6834

Background: Microbial synthesis of oleochemicals derived from native fatty acid (FA) metabolism has presentedsignificant advances in recent years. Even so, native FA biosynthetic pathways often provide a narrow variety of usuallylinear hydrocarbons, thus yielding end products with limited structural diversity. To overcome this limitation, we tookadvantage of a polyketide synthase-based system from Mycobacterium tuberculosis and developed an Escherichiacoli platform with the capacity to synthesize multimethyl-branched long-chain esters (MBE) with novel chemicalstructures.Results: With the aim to initiate the characterization of these novel waxy compounds, here, we describe the chassisoptimization of the MBE producer E. coli strain for an up-scaled oil production. By carrying out systematic metabolicengineering, we improved the final titer to 138.1 ± 5.3 mg MBE L−1 in batch cultures. Fed-batch microbial fermentationprocess was also optimized achieving a maximum yield of 790.2 ± 6.9 mg MBE L−1 with a volumetric productivityof 15.8 ± 1.1 mg MBE (L h)−1. Purified MBE oil was subjected to various physicochemical analyses, includingdifferential scanning calorimetry (DSC) and pressurized-differential scanning calorimetry (P-DSC) studies.Conclusions: The analysis of the pour point, DSC, and P-DSC data obtained showed that bacterial MBE possessimproved cold flow properties than several plant oils and some chemically modified derivatives, while exhibiting highoxidation stability at elevated temperatures. These encouraging data indicate that the presence of multiple methylbranches in these novel esters, indeed, conferred favorable properties which are superior to those of linear esters.Keywords: Escherichia coli, Wax production, Metabolic engineering, Fed-batch fermentation, Oleochemicals