Engineered E. coli W enables efficient 2,3-butanediol production from glucose and sugar beet molasses using defined minimal medium as economic basis

Abstract

BackgroundEfficient microbial production of chemicals is often hindered by the cytotoxicity of the products or by the pathogenicity of the host strains. Hence 2,3-butanediol, an important drop-in chemical, is an interesting alternative target molecule for microbial synthesis since it is non-cytotoxic. Metabolic engineering of non-pathogenic and industrially relevant microorganisms, such as Escherichia coli, have already yielded in promising 2,3-butanediol titers showing the potential of microbial synthesis of 2,3-butanediol. However, current microbial 2,3-butanediol production processes often rely on yeast extract as expensive additive, rendering these processes infeasible for industrial production.ResultsThe aim of this study was to develop an efficient 2,3-butanediol production process with E. coli operating on the premise of using cost-effective medium without complex supplements, considering second generation feedstocks. Different gene donors and promoter fine-tuning allowed for construction of a potent E. coli strain for the production of 2,3-butanediol as important drop-in chemical. Pulsed fed-batch cultivations of E. coli W using microaerobic conditions showed high diol productivity of 4.5 g l−1 h−1. Optimizing oxygen supply and elimination of acetoin and by-product formation improved the 2,3-butanediol titer to 68 g l−1, 76% of the theoretical maximum yield, however, at the expense of productivity. Sugar beet molasses was tested as a potential substrate for industrial production of chemicals. Pulsed fed-batch cultivations produced 56 g l−1 2,3-butanediol, underlining the great potential of E. coli W as production organism for high value-added chemicals.ConclusionA potent 2,3-butanediol producing E. coli strain was generated by considering promoter fine-tuning to balance cell fitness and production capacity. For the first time, 2,3-butanediol production was achieved with promising titer, rate and yield and no acetoin formation from glucose in pulsed fed-batch cultivations using chemically defined medium without complex hydrolysates. Furthermore, versatility of E. coli W as production host was demonstrated by efficiently converting sucrose from sugar beet molasses into 2,3-butanediol.Electronic supplementary materialThe online version of this article (10.1186/s12934-018-1038-0) contains supplementary material, which is available to authorized users.

Microbial Upgrading of Acetate into 2,3-Butanediol and Acetoin by E. coli W

“…No production from acetate on complex medium containing yeast extract In a previous study, 2,3-butandediol production from glucose was successfully established on chemically de ned medium [6]. The two most promising strains, Escherichia coli W 445_Ediss (W) and E. coli W ΔldhA ΔadhE Δpta ΔfrdA 445_Ediss (Δ4) were therefore chosen to investigate product formation from acetate.…”

“…Although 2,3-butanediol can be produced naturally by e.g. Klebsiella oxytoca or Enterobacter cloacae, some hosts are pathogenic and require complex and expensive media additives [6]. Therefore, 2,3-butanediol production has recently been developed in Escherichia coli [6][7][8].…”

“…Klebsiella oxytoca or Enterobacter cloacae, some hosts are pathogenic and require complex and expensive media additives [6]. Therefore, 2,3-butanediol production has recently been developed in Escherichia coli [6][7][8]. Since E. coli is not a natural producer, a heterologous pathway consisting of three genes has to be overexpressed: acetolactate synthase, acetolactate decarboxylase and butanediol dehydrogenase ( Fig.…”

“…1) [9]. So far, 2,3-butanediol has been produced from glucose [7,8] and alternative sugar sources such as sugar beet molasse [6].…”

A robust flow cytometry-based biomass monitoring tool enables rapid at-line characterization of S. cerevisiae physiology during continuous bioprocessing of spent sulfite liquor

“…Substrate and metabolite concentrations in the culture broth were measured as described previously by Erian et al [40], using an Ultimate 3000 system (Thermo Scientific, Waltham/ MA, USA) using an Aminex HPX-87H column (300 × 7.8 mm, Bio-Rad, Hercules, CA, USA).…”