Strain evolution and novel downstream processing with integrated
catalysis enable highly efficient co-production of 1,3-Propanediol and
organic acid esters from crude glycerol
Abstract
Bioconversion process with a single target product often lacks economic
competitiveness owing to incomplete use of raw material and high costs
of downstream processing (DSP). Here, we show with the microbial
conversion of crude glycerol that an integrated strain engineering and
catalytic conversion of the so-called byproducts can greatly improve DSP
and the process economy. Specifically, Clostridium pasteurianum was
first adapted to increased concentration of crude glycerol in a novel
automatic laboratory evolution system. At m3 scale bioreactor the strain
achieved a simultaneous production of 1,3-propanediol (PDO), acetic and
butyric acids at 81.21, 18.72 and 11.09 g/L within only 19 h,
respectively, representing the most efficient fermentation of crude
glycerol to targeted products. A heterogeneous catalytic step was
developed and integrated into the DSP process to obtain high-value
methyl esters from acetic and butyric acids at high yields. The
co-production of the esters also greatly simplified the recovery of PDO.
For example, a cosmetic grade PDO (96% PDO) was easily obtained by a
simple single-stage distillation process (with an overall yield more
than 77%). This integrated approach provides an industrially attractive
route for a complete use of the raw material with the simultaneous
production of three appealing products which greatly improve the process
economy and ecology.