Valorization of pyrolysis water: a biorefinery side stream, for 1,2-propanediol production with engineered Corynebacterium glutamicum

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DOI: {10.1186/s13068-017-0969-8}


Background: A future bioeconomy relies on the efficient use of renewable resources for energy and material product supply. In this context, biorefineries have been developed and play a key role in converting lignocellulosic residues. Although a holistic use of the biomass feed is desired, side streams evoke in current biorefinery approaches. To ensure profitability, efficiency, and sustainability of the overall conversion process, a meaningful valorization of these materials is needed. Here, a so far unexploited side stream derived from fast pyrolysis of wheat straw-pyrolysis water-was used for production of 1,2-propanediol in microbial fermentation with engineered Corynebacterium glutamicum. Results: A protocol for pretreatment of pyrolysis water was established and enabled growth on its major constituents, acetate and acetol, with rates up to 0.36 +/- 0.04 h(-1). To convert acetol to 1,2-propanediol, the plasmid pJULgldA expressing the glycerol dehydrogenase from Escherichia coli was introduced into C. glutamicum. 1,2-propanediol was formed in a growth-coupled biotransformation and production was further increased by construction of C. glutamicum.pqo.aceE.ldhA.mdh pJULgldA. In a two-phase aerobic/microaerobic fed-batch process with pyrolysis water as substrate, this strain produced 18.3 +/- 1.2 mM 1,2-propanediol with a yield of 0.96 +/- 0.05 mol 1,2-propanediol per mol acetol and showed an overall volumetric productivity of 1.4 +/- 0.1 mmol 1,2-propanediol -L-1 h(-1). Conclusions: This study implements microbial fermentation into a biorefinery based on pyrolytic liquefaction of lignocellulosic biomass and accesses a novel value chain by valorizing the side stream pyrolysis water for 1,2-PDO production with engineered C. glutamicum. The established bioprocess operated at maximal product yield and accomplished the so far highest overall volumetric productivity for microbial 1,2-PDO production with an engineered producer strain. Besides, the results highlight the potential of microbial conversion of this biorefinery side stream to other valuable products.



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