Metabolic Engineering of <i>E. coli</i> for Enhanced Diols Production from Acetate

Effective employment of renewable carbon sources is highly demanded to develop sustainable biobased manufacturing. Here, we developed <i>Escherichia coli</i> strains to produce 2,3-butanediol and acetoin (collectively referred to as diols) using acetate as the sole carbon source by stepwise metabolic engineering. When tested in fed-batch experiments, the strain overexpressing the entire acetate utilization pathway was found to consume acetate at a 15% faster rate (0.78 ± 0.05 g/g/h) and to produce a 35% higher diol titer (1.16 ± 0.01 g/L) than the baseline diols-producing strain. Moreover, singularly overexpressing the genes encoding alternative acetate uptake pathways as well as alternative isoforms of genes in the malate-to-pyruvate pathway unveiled that leveraging <i>ackA-pta</i> and <i>maeA</i> is more effective in enhancing acetate consumption and diols production, compared to <i>acs</i> and <i>maeB</i>. Finally, the increased substrate consumption rate and diol production obtained in flask-based experiments were confirmed in bench-scale bioreactors operated in fed-batch mode. Consequently, the highest titer of 1.56 g/L achieved in this configuration increased by over 30% compared to the only other similar effort carried out so far.